How long should air conditioner run?

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How long should air conditioner run?

Postby Triple digit golfer » Sun Apr 10, 2011 4:41 pm

I am in a new place since last summer and I am using the A/C for the first time today. I am not sure if there is something wrong with the thermostat, but it's about 80 degrees outside, so not too hot, yet the A/C seems to go on and off every ten minutes. It seems very frequent to me. The thermostat will say the temperature in here is 73 degrees, then it turns off, and by the time it turns back on ten minutes later, it already says it is 76. I don't think it's likely that it is warming up three degrees from the A/C being off for only ten minutes...although maybe it is.

Any ideas what the problem might be (if any)? In the winter it did not seem like the blower was running that frequently. It seemed like it ran longer but stayed off longer.
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Postby JDaniels » Sun Apr 10, 2011 4:56 pm

Is the stat in direct exposure to sunlight? Maybe another heat source? Is it on the top floor? Heat rises so even though it's only 80 outside, it may get hot quickly after the unit shuts off. Also, ASHRAE suggests to cool at 78. This might alleviate the constant start and stops.
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Postby Triple digit golfer » Sun Apr 10, 2011 4:59 pm

No direct sunlight on the thermostat. I am on the second floor of a building with six units.

I don't mind the frequent starts and stops, but I am just wondering if it's normal or if there is something wrong. I've never lived on a second floor before so maybe that does have something to do with it.
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Postby magicmom » Sun Apr 10, 2011 5:01 pm

Some thermostats like mine have a number of degrees that adjusts before it comes on. Mine is set on 2 so if I have it set to come on at 87 it won't start till it gets to 89 and then run till it gets to 87. If yours is set on 1 that might make it come on more times.
Does that make any sense?
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Postby Triple digit golfer » Sun Apr 10, 2011 5:04 pm

magicmom wrote:Some thermostats like mine have a number of degrees that adjusts before it comes on. Mine is set on 2 so if I have it set to come on at 87 it won't start till it gets to 89 and then run till it gets to 87. If yours is set on 1 that might make it come on more times.
Does that make any sense?


Absolutely. I was thinking about that. Maybe it is set to even less than 1. Maybe if I have it set to 73, once it gets to 73.1, it clicks on. I wouldn't even know how to check that. I'm in an apartment so maybe I'll check with the office.

It just went off at 3:46, then on at 3:53 and is still running now (4:04).
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Postby JDaniels » Sun Apr 10, 2011 5:08 pm

Triple digit golfer wrote:
magicmom wrote:Some thermostats like mine have a number of degrees that adjusts before it comes on. Mine is set on 2 so if I have it set to come on at 87 it won't start till it gets to 89 and then run till it gets to 87. If yours is set on 1 that might make it come on more times.
Does that make any sense?


Absolutely. I was thinking about that. Maybe it is set to even less than 1. Maybe if I have it set to 73, once it gets to 73.1, it clicks on. I wouldn't even know how to check that. I'm in an apartment so maybe I'll check with the office.

It just went off at 3:46, then on at 3:53 and is still running now (4:04).


That difference is called a "deadband". Usually, factory default is 2 degrees. Most people leave it since as you said, most people don't know how to change it. Definitely check it to make sure it is set to factory default of 2 degrees.
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Postby livesoft » Sun Apr 10, 2011 5:18 pm

Since you are renting, you should let management know your concerns.
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Postby Triple digit golfer » Sun Apr 10, 2011 5:21 pm

livesoft wrote:Since you are renting, you should let management know your concerns.


That's the plan. But they are such idiots I have little confidence they'll do anything other than come and click on the A/C and/or heat and tell me, "It's working."
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Postby magicmom » Sun Apr 10, 2011 5:29 pm

Maybe you can find directions for your thermostat online? It's called the temperature differential. I have my book but that probably won't be the same for yours.
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Postby infecto » Sun Apr 10, 2011 7:45 pm

I am confused. If it turns off @ 73 then turns back @ 76, why is there a concern about the deadband? Sounds like there is a thermal loss if the temperature is changing so drastically.
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Postby magellan » Sun Apr 10, 2011 9:04 pm

Is there an air duct blowing cool air directly onto the thermostat?

A three degree change in room temp in 10 minutes isn't normal and I'd focus on what's going on with that first. Maybe you could put a thermometer next to the thermostat just to verify that it's measuring the temperature accurately.

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(edited to fix spelling mistake)
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Re: How long should air conditioner run?

Postby fishnskiguy » Sun Apr 10, 2011 10:37 pm

Triple digit golfer wrote:I am in a new place since last summer and I am using the A/C for the first time today. I am not sure if there is something wrong with the thermostat, but it's about 80 degrees outside, so not too hot, yet the A/C seems to go on and off every ten minutes. It seems very frequent to me. The thermostat will say the temperature in here is 73 degrees, then it turns off, and by the time it turns back on ten minutes later, it already says it is 76. I don't think it's likely that it is warming up three degrees from the A/C being off for only ten minutes...although maybe it is.

Any ideas what the problem might be (if any)? In the winter it did not seem like the blower was running that frequently. It seemed like it ran longer but stayed off longer.


Sounds to me like there is very little insulation between your unit and the ones on either side. A three degree drop in ten minutes is a lot. Just guessing but when the tenants on either side turn on their A/C units, I'll bet yours will cycle less.

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Postby Slapshot » Sun Apr 10, 2011 10:49 pm

I'm envious that someone is using an air conditioner today.
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Postby englishgirl » Mon Apr 11, 2011 8:41 am

Slapshot wrote:I'm envious that someone is using an air conditioner today.


Well, but think of the expense. April has traditionally been my lowest electricity bill month, but this year so far I've had the A/C going every day. It seems like it's much hotter than previous years - I think it's going to be an expensive summer.

Anyway, TDG, 73 degrees? You should set it higher than that. There's no need to use up the electricity to cool the place to that low. Try a temp in the 75-78 range, which is better for the environment.

Also, are you on the top floor? I'd worry about attic insulation - could get very hot later in the summer if you don't have enough insulation, so ask the management about that too.
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Re: How long should air conditioner run?

Postby Parthenon » Mon Apr 11, 2011 10:38 am

Triple digit golfer wrote:I am in a new place since last summer and I am using the A/C for the first time today. I am not sure if there is something wrong with the thermostat, but it's about 80 degrees outside, so not too hot, yet the A/C seems to go on and off every ten minutes. It seems very frequent to me. The thermostat will say the temperature in here is 73 degrees, then it turns off, and by the time it turns back on ten minutes later, it already says it is 76. I don't think it's likely that it is warming up three degrees from the A/C being off for only ten minutes...although maybe it is.

Any ideas what the problem might be (if any)? In the winter it did not seem like the blower was running that frequently. It seemed like it ran longer but stayed off longer.


One way to smooth out the temperature fluctuations is to turn the fan on manually and leave it on. The air conditioner will still start and stop but maybe not that often.

The other issue, and I think this may be the problem besides the lack of insulation, is that perhaps the air conditioning unit is sized too big for the space being conditioned. It should run for a longer period of time in order to remove the moisture from the air which can lead to feeling cooler at a higher temperature setting on the thermostat.

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Postby TxAg » Mon Apr 11, 2011 12:40 pm

englishgirl wrote:
Slapshot wrote:I'm envious that someone is using an air conditioner today.


Well, but think of the expense. April has traditionally been my lowest electricity bill month, but this year so far I've had the A/C going every day. It seems like it's much hotter than previous years - I think it's going to be an expensive summer.

Anyway, TDG, 73 degrees? You should set it higher than that. There's no need to use up the electricity to cool the place to that low. Try a temp in the 75-78 range, which is better for the environment.

Also, are you on the top floor? I'd worry about attic insulation - could get very hot later in the summer if you don't have enough insulation, so ask the management about that too.



What's wrong with 73? He should be comfortable.

Mine is typically set around 75 during the day and 68-70 at night.

I rarely use the heat in the winter months, though.
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Postby englishgirl » Mon Apr 11, 2011 2:36 pm

What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.

Try an experiment of leaving the system off, and only get up and check what temperature it is when you feel uncomfortable. I've found that in winter I feel cold at 67, and in the summer I feel warm at 79. Maybe you run hotter than that (or you don't have the thin Florida blood) and you need it to be on 73, but maybe not.

Mine is set at 78 when I'm home (and I think 77 overnight), and 84 when I'm out during the day. It's very comfortable. OK, so when I get home I take off the cardigan or sweater that I wear all day at work, but really, we shouldn't be cooling our spaces so much that we need to wear sweaters in summer in the first place.
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Postby TxAg » Mon Apr 11, 2011 6:50 pm

I get hot easily. I refuse to be uncomfortable in my own home. Good thing I live in a 900 sf apt and not a 3000 sf house.
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Postby Triple digit golfer » Mon Apr 11, 2011 7:05 pm

englishgirl wrote:Anyway, TDG, 73 degrees? You should set it higher than that. There's no need to use up the electricity to cool the place to that low. Try a temp in the 75-78 range, which is better for the environment.


I set it where I'm comfortable. Higher than 73 is too warm for me. I feel there is a need to use up electricity to cool the place to 73 because any warmer is uncomfortable for me. Screw the environment! :)
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Re: How long should air conditioner run?

Postby Triple digit golfer » Mon Apr 11, 2011 7:07 pm

Parthenon wrote:One way to smooth out the temperature fluctuations is to turn the fan on manually and leave it on. The air conditioner will still start and stop but maybe not that often.


I never understood this. If you leave it on, how will it start and stop?
If it does, how does "on" differ from "auto?" Thanks.
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Postby Triple digit golfer » Mon Apr 11, 2011 7:09 pm

englishgirl wrote:What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.


There's no need to run it that low for YOU to be comfortable.

I don't care about the planet or my bottom line when it comes to being comfortable in my own home. I'll spend as much as it takes and ruin the planet as much as I need to in order to be comfortable.
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Re: How long should air conditioner run?

Postby infecto » Mon Apr 11, 2011 7:24 pm

Triple digit golfer wrote:
Parthenon wrote:One way to smooth out the temperature fluctuations is to turn the fan on manually and leave it on. The air conditioner will still start and stop but maybe not that often.


I never understood this. If you leave it on, how will it start and stop?
If it does, how does "on" differ from "auto?" Thanks.


It does not stop. The air circulation continues to run but the actual a/c will still cycle. IMO, not worth keeping on.
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Re: How long should air conditioner run?

Postby Triple digit golfer » Mon Apr 11, 2011 7:58 pm

infecto wrote:
Triple digit golfer wrote:
Parthenon wrote:One way to smooth out the temperature fluctuations is to turn the fan on manually and leave it on. The air conditioner will still start and stop but maybe not that often.


I never understood this. If you leave it on, how will it start and stop?
If it does, how does "on" differ from "auto?" Thanks.


It does not stop. The air circulation continues to run but the actual a/c will still cycle. IMO, not worth keeping on.


Got it, thank you.
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Postby rfburns » Mon Apr 11, 2011 8:02 pm

Do you live in a southern or coastal climate i.e., humid locale? If so it may be the A/C is working hard at removing the latent heat (humidity from the air, carpet, walls, etc.). It must come out first. You said you just turned it on so give it a day or two. If it is still acting the same, then yes something is wrong.

I'll spend as much as it takes and ruin the planet as much as I need to in order to be comfortable.


You won't want to go there. From your description it will soon be running non-stop. :shock:
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Postby In The Weeds » Mon Apr 11, 2011 10:03 pm

I tend to want to say you have cold air being directed toward the thermostat...but if heat were delivered threw the same ductwork it would be logical you would experience the same with the heating....
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Postby natureexplorer » Mon Apr 11, 2011 10:32 pm

Triple digit golfer wrote:
livesoft wrote:Since you are renting, you should let management know your concerns.
That's the plan. But they are such idiots I have little confidence they'll do anything other than come and click on the A/C and/or heat and tell me, "It's working."
You might want to watch your electricity consumption on your bill closely. It sounds like your place might be poorly insulated.
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Postby englishgirl » Mon Apr 11, 2011 10:50 pm

Triple digit golfer wrote:
englishgirl wrote:What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.


There's no need to run it that low for YOU to be comfortable.

I don't care about the planet or my bottom line when it comes to being comfortable in my own home. I'll spend as much as it takes and ruin the planet as much as I need to in order to be comfortable.


Then there's no need to worry about the A/C running too often or about insulation or a faulty thermostat if neither the environment nor money is a concern, and the whole thread is unnecessary. In fact, you might prefer it if it breaks down a little more and runs constantly, as you'll always have a nice cool breeze blowing on you.

And I never said to run it at a temperature at which you are uncomfortable. I said to check the thermostat to see what temperature it is when you are uncomfortable, with the implication (being that I am uncomfortable at 79, and therefore run mine at 77 or 78 ) that you should set it slightly below that.

Thanks for the kind thoughts about the planet, by the way.
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Postby infecto » Mon Apr 11, 2011 11:41 pm

englishgirl wrote:
Triple digit golfer wrote:
englishgirl wrote:What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.


There's no need to run it that low for YOU to be comfortable.

I don't care about the planet or my bottom line when it comes to being comfortable in my own home. I'll spend as much as it takes and ruin the planet as much as I need to in order to be comfortable.


Then there's no need to worry about the A/C running too often or about insulation or a faulty thermostat if neither the environment nor money is a concern, and the whole thread is unnecessary. In fact, you might prefer it if it breaks down a little more and runs constantly, as you'll always have a nice cool breeze blowing on you.

And I never said to run it at a temperature at which you are uncomfortable. I said to check the thermostat to see what temperature it is when you are uncomfortable, with the implication (being that I am uncomfortable at 79, and therefore run mine at 77 or 78 ) that you should set it slightly below that.

Thanks for the kind thoughts about the planet, by the way.



hahahahaha best reply ever. +1
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Postby campy2010 » Tue Apr 12, 2011 1:15 am

I live in an expensive electricity state and my first reaction was 'ouch my wallet' not 'what about the environment?' I'm curious, what is your monthly electric bill for an early summer month....say 80-85s outside and the ac kept at 73? What is the bill when its 90s-100s outside and the ac is kept at 73?
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Postby Triple digit golfer » Tue Apr 12, 2011 7:50 am

englishgirl wrote:
Triple digit golfer wrote:
englishgirl wrote:What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.


There's no need to run it that low for YOU to be comfortable.

I don't care about the planet or my bottom line when it comes to being comfortable in my own home. I'll spend as much as it takes and ruin the planet as much as I need to in order to be comfortable.


Then there's no need to worry about the A/C running too often or about insulation or a faulty thermostat if neither the environment nor money is a concern, and the whole thread is unnecessary. In fact, you might prefer it if it breaks down a little more and runs constantly, as you'll always have a nice cool breeze blowing on you.

And I never said to run it at a temperature at which you are uncomfortable. I said to check the thermostat to see what temperature it is when you are uncomfortable, with the implication (being that I am uncomfortable at 79, and therefore run mine at 77 or 78 ) that you should set it slightly below that.

Thanks for the kind thoughts about the planet, by the way.


I did all that already. 73 is the magic number.

And yes, you did say to set it at an uncomfortable temperature. You said it's not necessary to set it as low as 73. Anything higher than 73 is uncomfortable for me.

Regarding the thread being unnecessary: Nothing on this board is necessary. I am not concerned with the energy bills. I am concerned with something being mechanically wrong with the air conditioner or thermostat.

As for my comments about the planet...I'm sorry if you disagree, but my comfort comes before the health of the planet.

Thanks for your comments and suggestions earlier in the thread (seriously).
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Postby Triple digit golfer » Tue Apr 12, 2011 7:52 am

campy2010 wrote:I live in an expensive electricity state and my first reaction was 'ouch my wallet' not 'what about the environment?' I'm curious, what is your monthly electric bill for an early summer month....say 80-85s outside and the ac kept at 73? What is the bill when its 90s-100s outside and the ac is kept at 73?


Not sure, because this will be my first summer here. In the past, it was anywhere from $80-120, depending on the temperature.
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Postby infecto » Tue Apr 12, 2011 8:41 am

Triple digit golfer wrote:
campy2010 wrote:I live in an expensive electricity state and my first reaction was 'ouch my wallet' not 'what about the environment?' I'm curious, what is your monthly electric bill for an early summer month....say 80-85s outside and the ac kept at 73? What is the bill when its 90s-100s outside and the ac is kept at 73?


Not sure, because this will be my first summer here. In the past, it was anywhere from $80-120, depending on the temperature.


Since it is an apartment the be st you can do is tell maintenance. You could always get a thermometer and measure the change but the only problem with the thermostat would be skipping temperatures levels. Not even sure if thats possible but I guess anything is.
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Postby Valuethinker » Tue Apr 12, 2011 10:49 am

TxAg wrote:I get hot easily. I refuse to be uncomfortable in my own home. Good thing I live in a 900 sf apt and not a 3000 sf house.


It's likely the key is the humidity in Houston rather than the raw temperature.

Humidity has a huge impact on our subjective experience of cold and heat.

Outside of direct sunlight, there's lots of places that are thermally hot, but dry.

Conversely in a humid place, air conditioning feels like a necessity rather than a luxury. Step forward probably 60-70% Continental USA in summer (if not 90%).
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Postby Valuethinker » Tue Apr 12, 2011 10:55 am

englishgirl wrote:What's wrong with 73? We are a nation of energy hogs, and there's no need to run it that low to be comfortable - it's just using extra electricity. It will be more economical to run it at a higher temperature, so it's not just good for the planet but good for your bottom line too.

Try an experiment of leaving the system off, and only get up and check what temperature it is when you feel uncomfortable. I've found that in winter I feel cold at 67, and in the summer I feel warm at 79. Maybe you run hotter than that (or you don't have the thin Florida blood) and you need it to be on 73, but maybe not.

Mine is set at 78 when I'm home (and I think 77 overnight), and 84 when I'm out during the day. It's very comfortable. OK, so when I get home I take off the cardigan or sweater that I wear all day at work, but really, we shouldn't be cooling our spaces so much that we need to wear sweaters in summer in the first place.


Welcome to the 'rebound effect' aka Jevons effect.

Studies show that when British people replace their windows with double glazing, or improve their insulation, they then increase their mean living room temperature.

The mean temperature of an English living room in winter has risen by something like 7 degrees C (16 or so Fahrenheit) in the last 40 years-- to about 20 degrees C (68F).

That's the general problem with conservation. More fuel efficient cars tends to mean we drive more, for example (Vehicle Miles Travelled is directly correlated with GDP growth *but* that relationship has flattened out in the USA since about 2000).

I tend to focus on the 'big wins'.

I don't use my lights more if I have LED spots over halogen spots-- that's a 95% energy saving. Had I AC, it would be even more than that (ridiculously more, because a 50 watt halogen costs another 15-25 watts in air conditioning to remove that heat).

I don't use my fridge more if it is a modern one, which consumes 1/3rd the energy of a 1980 fridge (1/4 is possible). Even at (low) US power rates, posters here report savings of c. $20 pcm by switching a 20+ year old fridge to a new one.

Air con is tricky. In an American climate (humid, generally) people are going to want to run AC.

But if the AC is wrongly sized or badly set, it may run too much-- the impression of comfortable rooms is distorted if the humidity is not being properly controlled.
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Postby Tdad » Tue Apr 12, 2011 11:34 am

Sounds the OP got short cycles.

Also, if possible, call an energy auditor to do blower testing and make sure that all ducts and the whole house are air tight, otherwise, you are wasting money on electric bills.
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Re: How long should air conditioner run?

Postby UrbanMedic » Tue Apr 12, 2011 11:50 am

Triple digit golfer wrote:I am in a new place since last summer and I am using the A/C for the first time today. I am not sure if there is something wrong with the thermostat, but it's about 80 degrees outside, so not too hot, yet the A/C seems to go on and off every ten minutes. It seems very frequent to me. The thermostat will say the temperature in here is 73 degrees, then it turns off, and by the time it turns back on ten minutes later, it already says it is 76. I don't think it's likely that it is warming up three degrees from the A/C being off for only ten minutes...although maybe it is.

Any ideas what the problem might be (if any)? In the winter it did not seem like the blower was running that frequently. It seemed like it ran longer but stayed off longer.


It could be the AC is crappy and poorly maintained. This is typical of apartments. In most places AC is considered a necessity, but it doesn't have to be good AC or efficient AC. The system needs to be checked and probably recharged with refrigerant. If this isn't done routinely, there's just not enough gas in the pipes to go a good job cooling your place. A guy who used to down the street from us kept his house at, I kid you not, 62 degrees year round. I can't imagine the bill. But in any case, he always had someone out once a spring to recharge his AC and it usually needed it. The thing was running almost 18 hours a day for 6 months a year.

Check your air filters, vacuum out what you can in your furnace / AC unit. You might look into getting a window unit if your appeals to management are unsuccessful. In your case, it might be more cost effective.
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Postby Valuethinker » Tue Apr 12, 2011 11:59 am

natureexplorer wrote:
Triple digit golfer wrote:
livesoft wrote:Since you are renting, you should let management know your concerns.
That's the plan. But they are such idiots I have little confidence they'll do anything other than come and click on the A/C and/or heat and tell me, "It's working."
You might want to watch your electricity consumption on your bill closely. It sounds like your place might be poorly insulated.


OP can get a gadget which measures electricity consumption of one appliance (or one for the whole apartment, and then see what happens when AC kicks in).

In the UK, the big swing factor is the electric kettle (5-10% household consumption).

In the US, you don't have those. But you do have AC.

Our per household average is 4800kwhrs and yours is roughly 11-12,000 (highly dependent on geography). The difference, other than larger house sizes generally, is largely to do with AC.

If feels like OP has a seriously effed AC and is going to be paying that through the nose in higher electricity bills.

I suspect a broken thermostat but it could be something worse.

Any idea how old the AC is? Check model number online?

The EIA Energy Star website will give you an estimate of the cost pcm of running that, once you have the model number. Does that check out?
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Re: How long should air conditioner run?

Postby Valuethinker » Tue Apr 12, 2011 12:01 pm

Triple digit golfer wrote:I am in a new place since last summer and I am using the A/C for the first time today. I am not sure if there is something wrong with the thermostat, but it's about 80 degrees outside, so not too hot, yet the A/C seems to go on and off every ten minutes. It seems very frequent to me. The thermostat will say the temperature in here is 73 degrees, then it turns off, and by the time it turns back on ten minutes later, it already says it is 76. I don't think it's likely that it is warming up three degrees from the A/C being off for only ten minutes...although maybe it is.

Any ideas what the problem might be (if any)? In the winter it did not seem like the blower was running that frequently. It seemed like it ran longer but stayed off longer.


It really does sound like your thermostat is broken.

Get a separate thermometer, and check air temperatures against it.
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Postby UrbanMedic » Tue Apr 12, 2011 12:36 pm

Valuethinker wrote:
OP can get a gadget which measures electricity consumption of one appliance (or one for the whole apartment, and then see what happens when AC kicks in).



Meritline.com was selling the Kill-A-Watt for about $20 shipped. I just bought one the other day to figure out why our electrical bill was so high. We pay about 12 cents per kwh above 1,000 in the summer.

Just for those interested, here's a list of things I measured:
1500 watt electric tea kettle. To boil 1 liter of water taken from the tap - about 10 cents.

Vacuum is about 1100 watts. I vacuum once a day, sometimes twice if its messy. About 2 cents per vacuum session.

Dryer is 220v and I couldn't plug it into the dryer, but the heater element is rated at 5800 watts. Since its electric, efficiency is close to 100%. So that's a bit pricey at about 69 cents per hour of use. This does not take into account any heat spill into the house that add to AC loads or subtract from heating.

Central AC -- can't measure it directly. Same is true for the blower. I could turn off everything else in the house and kick it on for 15 minutes and check the meter.

Older tube television -- during use 110-120 watts. Standby (one of those always on TVs) 1.5 watts.

Electric blanket. Regardless of setting, low med high, it is always 50 watts. Even when not in use, it draws 0.5 watts. This was most puzzling. I figured a, it would use more. b, that the setting changed its power consumption. I don't understand why.

Netbook surfing internet. 14 watts. Watching full screen HD movie, 21 watts.

Deep freeze. Very very cheap. 10 cents per day. It used 0.5kwh for 13 hours of use.

Fridge -- I suspect it is a big user. It runs quite frequently and draws about 150-250 watts. I have not checked it over a 24 hour period yet, but was cleaning off the radiator coils in back to see if that helps.

Stove is 220v, so I can't measure that. I think the oven uses as much electricity as the dryer.

Cable modem + wireless router is almost nonexistent use. About a penny per day.

Lighting. CFL mostly. Not even worth measuring its so little.

Cell phone charge. Ditto with lights.

Oil filled space heater. About 1450 watts on high setting. 610 watts on low.

So the biggest users I can come up with are the electric range and oven, fridge (only because it runs quite frequently), the dryer, and my guess of central heat and cooling.

We got a clothes line for the backyard to help limit the amount of dryer use, started using the microwave more instead of the oven, and when possible cooking things out doors. I have a little kerosene stove I use on the patio. This makes me happy because I like old stoves, keeps the house from smelling funny from cooking smells, and helps avoid putting a lot of heat into the house when its hot. But with kerosene selling at $5 / gallon, it's debatable if it really saves all that much. I priced it per million BTU and kero is about $36 per million BTU at 100% efficiency vs $18 per million for electric. Propane is about $2.10 per gallon, so that's about $23 per million BTU. This is bulk residential prices. A typical 20 lb tank will really hold somewhere about 16-18 lbs in my experience and they are seldom truly empty. Propane weighs about 4.5 pounds per gallon at 65 degrees I think, so a tank is but 4 gallons of propane. They sell for about $20 on the swap tank racks, or about $5 per gallon. That makes it about $54 per million BTU which is way higher than I would have guessed. Long and short, electricity and natural gas are cheap.

--

Edit, I just priced charcoal. I get 46 lbs for $17. 1 lb = 9,000 BTU. Thus it is appx $41 per million BTU at 100% efficiency. I don't know what at typical grill yields in terms of efficiency, but I guess not too high.
Last edited by UrbanMedic on Tue Apr 12, 2011 12:55 pm, edited 1 time in total.
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Postby infecto » Tue Apr 12, 2011 12:48 pm

UrbanMedic wrote:
Deep freeze. Very very cheap. 10 cents per day. It used 0.5kwh for 13 hours of use.

Fridge -- I suspect it is a big user. It runs quite frequently and draws about 150-250 watts. I have not checked it over a 24 hour period yet, but was cleaning off the radiator coils in back to see if that helps.



Funny you mention this. I always wanted to take a chest freezer and change the thermostat to run like a fridge then just use it as a fridge. Compared to a standup fridge, they use next to nothing.
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Postby campy2010 » Tue Apr 12, 2011 1:00 pm

Triple digit golfer wrote:
campy2010 wrote:I live in an expensive electricity state and my first reaction was 'ouch my wallet' not 'what about the environment?' I'm curious, what is your monthly electric bill for an early summer month....say 80-85s outside and the ac kept at 73? What is the bill when its 90s-100s outside and the ac is kept at 73?


Not sure, because this will be my first summer here. In the past, it was anywhere from $80-120, depending on the temperature.


Not terrible. If I were to cool my house to these temps I would probably have a $200-$300 electricity bill. Of course, I live in a poorly-insulated rental.
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Postby Valuethinker » Tue Apr 12, 2011 1:07 pm

UrbanMedic wrote:
Valuethinker wrote:
OP can get a gadget which measures electricity consumption of one appliance (or one for the whole apartment, and then see what happens when AC kicks in).



OK the thing to drill down on is your fridge.

*that*, if it is old, will burn watts. And ditto a separate freezer.


http://www.energystar.gov/index.cfm?fus ... gw_code=RF

On the right hand side, a spreadsheet that will estimate savings of upgrade if you own a pre 1992 model (or pre 1998 even).

You just need the model number.

Meritline.com was selling the Kill-A-Watt for about $20 shipped. I just bought one the other day to figure out why our electrical bill was so high. We pay about 12 cents per kwh above 1,000 in the summer.


I pay about 22 cents US for *all* my power ;-).


Dryer is 220v and I couldn't plug it into the dryer, but the heater element is rated at 5800 watts. Since its electric, efficiency is close to 100%. So that's a bit pricey at about 69 cents per hour of use. This does not take into account any heat spill into the house that add to AC loads or subtract from heating.


They burn. I assume yours is vented to the outside? If not, they really are inefficient.

On 'efficiency' not 100%: you have to turn the tumbler. But yes, most of the electricity gets turned into heat.

Central AC -- can't measure it directly. Same is true for the blower. I could turn off everything else in the house and kick it on for 15 minutes and check the meter.


If it's an old system, or badly installed, then you really could be burning.

Older tube television -- during use 110-120 watts. Standby (one of those always on TVs) 1.5 watts.


Looks way too low but it might be so (maybe the standbyes weren't so inefficient-- the plasma screen standbyes, and the early Set Top Boxes, were horrifying).

Electric blanket. Regardless of setting, low med high, it is always 50 watts. Even when not in use, it draws 0.5 watts. This was most puzzling. I figured a, it would use more. b, that the setting changed its power consumption. I don't understand why.


And it's a safety worry. Put it on a power bar and turn it off when not in use. And consider a replacement.


Deep freeze. Very very cheap. 10 cents per day. It used 0.5kwh for 13 hours of use.


Mine burns 180 kwhr pa (but it's only 110 litres, and front opening). A modern chest freezer can be *very* efficient.

Fridge -- I suspect it is a big user. It runs quite frequently and draws about 150-250 watts. I have not checked it over a 24 hour period yet, but was cleaning off the radiator coils in back to see if that helps.


As above. What age? A 1940 fridge used 500 kwhr pa. A 1970 one, 2000 kwhr (yes, that's $20 pcm at your rate), a 2011 one (efficient) 550-750 kwhr (much bigger than the 1940 model).

Stove is 220v, so I can't measure that. I think the oven uses as much electricity as the dryer.


They'll be a watts on the fuse. Watts x hours in use = watt hours. Divide by 1000 = kwhr. 100% conversion into heat.

Cable modem + wireless router is almost nonexistent use. About a penny per day.


Modern. The early ones were horrific.

Lighting. CFL mostly. Not even worth measuring its so little.


Query. 15 watt bulb. 65 hours is 1 kwhr. Not nothing.

Cell phone charge. Ditto with lights.

Oil filled space heater. About 1450 watts on high setting. 610 watts on low.


Sounds about right.

Electric blanket and space heater?

Do you live in an uninsulated house? Cold climate? UK these are normal *but* our houses were basically uninsulated.

So the biggest users I can come up with are the electric range and oven, fridge (only because it runs quite frequently), the dryer, and my guess of central heat and cooling.


You should be able to find the range from the manual-- the wattage.

We got a clothes line for the backyard to help limit the amount of dryer use, started using the microwave more instead of the oven, and when possible cooking things out doors. I have a little kerosene stove I use on the patio.


Unless natural gas then a BBQ is not likely to be cheaper than a stove. Natural gas is c. 3 cents/kwhr in US (I think). Propane is priced off oil-- and much much closer per kwhr. (EIA does publish prices).

Microwave is roughly 50% efficient. Over a stove, it saves power because the heat is concentrated in the food, not all over the kitchen. But for some things (many) it just is not as good or does not work.

I really doubt your range is it. And of course in winter, it's supplementary electric heat.

If you heat in winter by electric bar heating that will *drink* electricity. Wattage x hours used.

Air Sourced Heat Pump (you can get ones that do air to hot water heating if you have rads) will help. That can move 3 watts of heat for every watt burned. Below low single digit F, electric bar heating will kick in. Here LG and Mitsubishi dominate the market (and, generally, Mitsubishi are seen as the reliable supplier).

I presume you heat your water electrically? Insulating the water tank could save you a bit (especially if it's in a cold basement).

This makes me happy because I like old stoves, keeps the house from smelling funny from cooking smells, and helps avoid putting a lot of heat into the house when its hot. But with kerosene selling at $5 / gallon, it's debatable if it really saves all that much.


Generally kerosene will cost you money.

And kerosene raises huge safety issues-- Carbon Monoxide poisoning a very real threat-- kills thousands in the third world every year. And fire. Propane is explosive in certain circumstances.

Your house insurance may not cover use of a kerosene stove?

Had I pets or a child, I wouldn't use kerosene.

I priced it per million BTU and kero is about $36 per million BTU at 100% efficiency vs $18 per million for electric. Propane is about $2.10 per gallon, so that's about $23 per million BTU. This is bulk residential prices.


A kerosene stove is unlikely to have more than 70% combustion efficiency (energy in the fuel to usable heat). A propane burner can do in the 80s or even 90 but may well not do so.

A typical 20 lb tank will really hold somewhere about 16-18 lbs in my experience and they are seldom truly empty. Propane weighs about 4.5 pounds per gallon at 65 degrees I think, so a tank is but 4 gallons of propane. They sell for about $20 on the swap tank racks, or about $5 per gallon. That makes it about $54 per million BTU which is way higher than I would have guessed. Long and short, electricity and natural gas are cheap.


Natural gas is very cheap in most of USA. I pay about 4.5p/ kwhr so 6 cents which would be something over ? on Imperial.

Electricity you are bang on US average.

Depending on your climate, the prime suspects in your electricity bills are:

- the fridge
- the HVAC especially if you are using electric heat (an Air Source Heat Pump may well be worth it)

As ever check your loft insulation and hot water tank insulation. These are relatively easy to do something about, usually. Walls are harder. Storm windows help (a lot on the windy side of the house).

If you live in a hot climate, then awnings help on the south and uncovered east or west sides-- a lot. Like 10% of AC bill. Plus much greater comfort-- and my parents have retractible ones.

Also if you have flat roofs or roofs heavily exposed to southern sun. AC is so much more inefficient than heating, that even at NYC latitudes, it pays to switch from a black roof to a silver or white roof (bylaws permitting).

or put up a solar photovoltaic panel, which provides shade ;-).
Last edited by Valuethinker on Tue Apr 12, 2011 1:25 pm, edited 1 time in total.
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Postby Valuethinker » Tue Apr 12, 2011 1:14 pm

englishgirl wrote:Thanks for the kind thoughts about the planet, by the way.


If one wants to save the planet, then *anything* that does something about rainforest deforestation is so far far above anything we can do in our personal lives, in terms of carbon avoided, that you have to focus on that.

Rainforest Trust. Greenpeace. Various groups opposed to biofuels (biodiesel and the palm oil from which it is sourced, could finish off the Indonesian and Congolese rainforest by themselves). As Jane Goodall said at a recent public address I attended 'there is no such thing as sustainable palm oil'.

There are 3 rainforests left on the planet of size: Democratic Republic of Congo, Brasilian and adjacent Amazonia, Indonesia. The last is almost gone.

The only other impact you can possibly have of similar size would be to stop flying.

I went through this with the solar panel. Spent £10k, save 1 tonne of CO2 pa and consume £700 pa of subsidies.

That would be the same benefit to Planet Earth of saving less than 1 acre of rainforest, at a cost of £30, roughly.

I try to find groups that are prepared to fight, to preserve the rainforest.

it's not enough now to talk of personal virtue.
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Postby Valuethinker » Tue Apr 12, 2011 1:23 pm

infecto wrote:
UrbanMedic wrote:
Deep freeze. Very very cheap. 10 cents per day. It used 0.5kwh for 13 hours of use.

Fridge -- I suspect it is a big user. It runs quite frequently and draws about 150-250 watts. I have not checked it over a 24 hour period yet, but was cleaning off the radiator coils in back to see if that helps.



Funny you mention this. I always wanted to take a chest freezer and change the thermostat to run like a fridge then just use it as a fridge. Compared to a standup fridge, they use next to nothing.


Chest freezer will not, I don't think, run as a fridge (the problem being far more moisture to get rid of)?

What makes chest freezers work so well is:

- thick insulation
- not opened and closed very often relative to a fridge

That offsets the minus 18C that they run at.
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Postby UrbanMedic » Tue Apr 12, 2011 1:37 pm

Dryer is 220v and I couldn't plug it into the dryer, but the heater element is rated at 5800 watts. Since its electric, efficiency is close to 100%. So that's a bit pricey at about 69 cents per hour of use. This does not take into account any heat spill into the house that add to AC loads or subtract from heating.


They burn. I assume yours is vented to the outside? If not, they really are inefficient.

On 'efficiency' not 100%: you have to turn the tumbler. But yes, most of the electricity gets turned into heat.


Yes, exterior vent. I did experiment with venting it into the unheated garage in the hopes of recapturing the heat. This was a small disaster. That "lint trap" is in name only. My car looked like a lint sweater after it sat in the garage for 2 days after we did a lot of laundry. I did contemplate rigging up a metal box with a furnace filter on it to filter out the lint from the tubing, but decided this could be a real problem.

Stove is 220v, so I can't measure that. I think the oven uses as much electricity as the dryer.


They'll be a watts on the fuse. Watts x hours in use = watt hours. Divide by 1000 = kwhr. 100% conversion into heat.


11,500 watts. I assume that's everything on at once. All 4 burners and the oven.


Oil filled space heater. About 1450 watts on high setting. 610 watts on low.


Sounds about right.

Electric blanket and space heater?

Do you live in an uninsulated house? Cold climate? UK these are normal *but* our houses were basically uninsulated.


We use the electric blanket only to heat the bed up in the winter. For some reason, if my feet are cold, they want to stay cold all night and I can't sleep. There's nothing nicer than getting into a toasty warm bed. I fell asleep with it on once and woke up half cooked. The newer models have a 3 hour shutoff. You know some poor person fell asleep with it on and cooked themselves half to death.

Thanks for that link about the fridge. That's great stuff. It's a 2008 model, so the feds are saying 424 kwh annually. Not nearly what I thought.

The water heater is natural gas. We pay, currently (may rise shortly) $0.77 per therm. I think one therm is around 30 kwh. So about 2.5 cents per kwh? Seems like a steal.

22 cents is a princely sum if you ask me, but I don't know what typical rates are. This is what state or country? UK?
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Postby Valuethinker » Wed Apr 13, 2011 4:38 am

UrbanMedic wrote:
Dryer is 220v and I couldn't plug it into the dryer, but the heater element is rated at 5800 watts. Since its electric, efficiency is close to 100%. So that's a bit pricey at about 69 cents per hour of use. This does not take into account any heat spill into the house that add to AC loads or subtract from heating.


They burn. I assume yours is vented to the outside? If not, they really are inefficient.

On 'efficiency' not 100%: you have to turn the tumbler. But yes, most of the electricity gets turned into heat.


Yes, exterior vent. I did experiment with venting it into the unheated garage in the hopes of recapturing the heat. This was a small disaster. That "lint trap" is in name only. My car looked like a lint sweater after it sat in the garage for 2 days after we did a lot of laundry. I did contemplate rigging up a metal box with a furnace filter on it to filter out the lint from the tubing, but decided this could be a real problem.



And unsafe. Lint catches *fire*. Fire department always being called to house fires started by lint.

Stove is 220v, so I can't measure that. I think the oven uses as much electricity as the dryer.


They'll be a watts on the fuse. Watts x hours in use = watt hours. Divide by 1000 = kwhr. 100% conversion into heat.


11,500 watts. I assume that's everything on at once. All 4 burners and the oven.


Probably you are only using half of that at any given moment. Oven on for an hour, 5.5kwhr (remembering that the heat goes into the house, so in winter not such a problem).


Oil filled space heater. About 1450 watts on high setting. 610 watts on low.


Sounds about right.

Electric blanket and space heater?

Do you live in an uninsulated house? Cold climate? UK these are normal *but* our houses were basically uninsulated.


We use the electric blanket only to heat the bed up in the winter. For some reason, if my feet are cold, they want to stay cold all night and I can't sleep. There's nothing nicer than getting into a toasty warm bed. I fell asleep with it on once and woke up half cooked. The newer models have a 3 hour shutoff. You know some poor person fell asleep with it on and cooked themselves half to death.


It is trivial then, but safety precaustions are wise.

You are a doc, so you know, but cold feet can be a sign of poor circulation, diabetes etc?

Thanks for that link about the fridge. That's great stuff. It's a 2008 model, so the feds are saying 424 kwh annually. Not nearly what I thought.


There are embedded assumptions about how many times a day it is opened, how long it is opened for (the testers are not teenagers who talk on the phone whilst reorganizing the fridge in search of fodder).

The water heater is natural gas. We pay, currently (may rise shortly) $0.77 per therm. I think one therm is around 30 kwh. So about 2.5 cents per kwh? Seems like a steal.


US gas prices (wholesale) are around $4.50/ m btus. Because of shale gas, US gas prices have dropped like a tone. They are about half (or less) of UK gas prices.

Assume 2 teenagers. Your likely hot water consumption is around 5000 kwhr pa.

If you have natural gas, then that is normally far and away the cheapest way to heat your home. A modern furnace (check Energy Star website again as per previous link) can do 90% efficiency, but not worth upgrading if your current one is c. 80% (which it probably is if less than 15 years old-- you can check model numbers).

2.5 cents/ kwhr for gas, 12 cents for electricity: that would be about typical in the USA, I believe.

22 cents is a princely sum if you ask me, but I don't know what typical rates are. This is what state or country? UK?


UK GDP per capita is lower. Houses are smaller. Energy of all forms costs a lot more. However residential air con is almost unknown (mild climate) although I believe it will become common in London in the next 20-30 years.

Average usage per household is c. 4800kwhr pa for electricity. US I believe is around 12000 (but with huge regional variations).


I believe the average UK gas consumption is around 13000 kwhr pa (hot water would be about 3000-3500 kwhr of that). There are still US states without insulation standards in new construction. Conversely, the UK has an ancient housing stock: renovations and extensions must meet much stricter energy insulation requirements, and a new build home can use 1/5th the energy of a traditional home. But we still have c. 7m homes (1/4rd of the total) with no or minimal insulation (my walls are single brick thick, no cavity, no insulation).

The US average was just over 10.5 cents/ kwhr from memory. As low as 5 cents in the South and in places in the NW where there is plentiful hydro.

However New England, New York and California pay prices as high as the 20c+, with time of day variation.

Time of day pricing is becoming universal: the grid just cannot take the strain of the morning shift going home and turning on the TV and the air con up, whilst office buildings, stores and factories are still humming.

At that moment, peak plant kicks in (*if* the wires can take the current, which on a really hot day, they may not be able to-- it's a serious problem especially in big cities). Peak plant is straight through gas turbine-- 35% efficiency, and expensive. (gas turbines running mid merit or baseload run at 50%+ efficiency with the combined cycle running but are still relatively expensive).

Anything the utility can do to shave the peak is a disproportionate saving to the cost of electricity.

Wholesale electricity prices can be 30 cents/ kwhr at peak (100 is possible on a bad day) and 2 cents in the middle of the night (in fact, because nukes and wind have to pay the grid operator, they can go negative in night time). Add 5-6 cents/kwhr as your typical grid charge.

My best guess is your electricity bill is in your air con. I assume you are not heating with electricity, but if you are, then a switch to gas would almost certainly pay off (although you need a contractor's estimate of cost).

Remember energy savings are basically risk free, ie the right discount rate is around 4% (US Treasury Bonds) except you don't pay tax on energy savings.

For example swapping a 50watt halogen for a 3 watt LED in my kitchen ceiling, has a payback period of 18 months for me (it's a little worse than that, in the winter, the halogen is electric heat for the bedroom above the kitchen).
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Postby infecto » Wed Apr 13, 2011 9:32 am

Valuethinker wrote:Chest freezer will not, I don't think, run as a fridge (the problem being far more moisture to get rid of)?

What makes chest freezers work so well is:

- thick insulation
- not opened and closed very often relative to a fridge

That offsets the minus 18C that they run at.


Chest freezers will run as a fridge. Did it for my homebrew and it works great. Have not had the space to do it for a food fridge though. Hundreds if not thousands of people use chest freezers to keep their kegs cool though. I have seen a number of people use them as food fridges also.

And you are also incorrect on what makes them work so well. Sure not opening helps and thicker insulation always helps but the key is the orientation of the door. Every time you open a standup fridge you have a much larger thermal loss then you would opening a chest fridge. Even when closed there is less thermal loss just do to the orientation of the doors.
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Postby Valuethinker » Wed Apr 13, 2011 9:50 am

infecto wrote:
Valuethinker wrote:Chest freezer will not, I don't think, run as a fridge (the problem being far more moisture to get rid of)?

What makes chest freezers work so well is:

- thick insulation
- not opened and closed very often relative to a fridge

That offsets the minus 18C that they run at.


Chest freezers will run as a fridge. Did it for my homebrew and it works great. Have not had the space to do it for a food fridge though. Hundreds if not thousands of people use chest freezers to keep their kegs cool though. I have seen a number of people use them as food fridges also.

And you are also incorrect on what makes them work so well. Sure not opening helps and thicker insulation always helps but the key is the orientation of the door. Every time you open a standup fridge you have a much larger thermal loss then you would opening a chest fridge. Even when closed there is less thermal loss just do to the orientation of the doors.


Thanks

I was thinking gross, you are pointing out the delta (over my front opening freezer, for example). So thank you.

What you say makes good sense and interesting re 'homebrew'.
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Postby Valuethinker » Wed Apr 13, 2011 9:56 am

UrbanMedic wrote:ovens


http://www.carbonfootprint.com/energyconsumption.html

says 1.56kwhr per use.
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Postby infecto » Wed Apr 13, 2011 10:18 am

Valuethinker wrote:
infecto wrote:
Valuethinker wrote:Chest freezer will not, I don't think, run as a fridge (the problem being far more moisture to get rid of)?

What makes chest freezers work so well is:

- thick insulation
- not opened and closed very often relative to a fridge

That offsets the minus 18C that they run at.


Chest freezers will run as a fridge. Did it for my homebrew and it works great. Have not had the space to do it for a food fridge though. Hundreds if not thousands of people use chest freezers to keep their kegs cool though. I have seen a number of people use them as food fridges also.

And you are also incorrect on what makes them work so well. Sure not opening helps and thicker insulation always helps but the key is the orientation of the door. Every time you open a standup fridge you have a much larger thermal loss then you would opening a chest fridge. Even when closed there is less thermal loss just do to the orientation of the doors.


Thanks

I was thinking gross, you are pointing out the delta (over my front opening freezer, for example). So thank you.

What you say makes good sense and interesting re 'homebrew'.


Think might have changed but it was just something I read a while back. I know

The process of making it is quite easy. can either but a digital thermometer that you cut into the power line or you can just replace the original freezer with a fridge thermo.

Here is one guys creation. http://mtbest.net/chest_fridge.html
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