HVAC systems brands/electric heat pumps

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brak
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HVAC systems brands/electric heat pumps

Post by brak »

My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
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RickBoglehead
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Re: HVAC systems brands/electric heat pumps

Post by RickBoglehead »

Quite a few threads discussing this. Here's two:

viewtopic.php?t=333506

viewtopic.php?t=326987
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Re: HVAC systems brands/electric heat pumps

Post by galawdawg »

brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
The most important component of any HVAC system, including heat pumps, is quality installation. I'd recommend you seek out several well-recommended HVAC installers and contact them for an evaluation of your HVAC needs and quotes. There are quite a few different HVAC brands but many of them use the same major components (compressor, motors, control boards, etc).

York is a system that I recently had installed. If purchased from a York Certified Comfort Expert it will come with a ten (10) year parts AND labor warranty from York. Amana is another brand with a similar warranty, however, unlike York, Amana requires that you have annual service performed by an Amana dealer. York merely requires that the system be maintained as recommended (filter changes, coil cleaning as needed, etc). Most other brands only have a one (1) year labor warranty but will sell third-party extended warranties. York pricing was competitive with Trane, Lennox and the other major brands but included the longer warranty.

In your locale, an electric heat pump will likely be inadequate for heating requirements and you will need to either run the heat strips frequently (which can be costly) or go with a dual-fuel system that switches to natural gas or propane in very low temperatures.

Good luck!
adamthesmythe
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Re: HVAC systems brands/electric heat pumps

Post by adamthesmythe »

It's gets cold up there in Wisconsin. Research carefully the performance of a heat pump in your climate.
mgensler
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Re: HVAC systems brands/electric heat pumps

Post by mgensler »

Recommend reading up on mini-split heat pumps over at Greenbuildingadvisor.com. There are quite a few brands that are made for cold climates without backup heat. You can buy them in ducted and ductless versions. Fujitsu and Mitsubishi are the two well-regarded brands with extensive dealer/parts networks. There are a lot of other brands that are of good quality as well.
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Re: HVAC systems brands/electric heat pumps

Post by Broken Man 1999 »

When we bought our home, the entire neighborhood had Trane heat pumps, two-story homes with two heat pumps.

Currently I have two American Standard heat pumps. The color is different, Trane HPs were green, our American Standard HPs are grey.

Consumer Reports: Results in the following chart are gathered from Consumer Reports’ 2018 Winter and 2019 Summer Surveys of 12,463 heat pumps, owned by members who purchased a new unit between 2003 and 2019.

Category-Predicted Reliability: Trane and American Standard were the only two heat pumps to score 5/5. All other heat pumps scored 4/5 or lower.

Category-Owner Satisfaction: Trane and American Standard were the only two heat pumps to score 5/5. All other heat pumps scored 4/5 or lower.


OP, you will receive much anecdotal info, not as rigorous as Consumer Reports; still, I will add mine.

Our HPs have required repairs along the way, but very few. I have never considered any other brand. Living in Florida, we use our air conditioning more than most other states, and reliability is very important to me.

So, there was my anecdotal info!

Broken Man 1999
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Re: HVAC systems brands/electric heat pumps

Post by BolderBoy »

Recently had an American Standard (same as Trane) central AC replacement. 17 SEER model. The estimator said that going above 17 SEER involves a whole 'nother level of complexity and things to break. The installer was excellent (he put in my new furnace last October).

I agree with galawdawg - the installation quality is the most important consideration.
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Re: HVAC systems brands/electric heat pumps

Post by wfrobinette »

brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.
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Re: HVAC systems brands/electric heat pumps

Post by jpelder »

wfrobinette wrote: Wed Jul 21, 2021 2:09 pm
brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.
That's a good point. IIRC, the number is more like 20 degrees F now, but Wisconsin will have many days well below that. But a heat pump will save OP a lot in spring and fall.

I also agree that quality installation (both of the appliance and the ductwork) is the most important consideration. A well-installed budget brand is better than a poorly-installed Trane or American Standard. There are also some differences in thermostat compatibility among the brands (some work with Nest and similar, while others require their own brand).
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
That doesn't work in Wisconsin. You'll put less CO₂ into the atmosphere by heating your house with a gas furnace for most of the year.

Wisconsin gets 40% of its electricity from coal. The state's energy grid is so dirty that it puts out 630 grams of CO₂ per kWh. A natural gas furnace emits just 5.3 kg of CO₂ per therm, or 180 grams per kWh.

A heat pump in Wisconsin has to achieve a COP of at least 3.5 to reduce CO₂ emissions compared to a natural gas furnace. Even the Asian mini-split heat pumps don't get above 3.5 until about 50°F.

Wisconsin is very cold. The high temperature in Milwaukee is below 50°F from November to April. The low temperature is below 50°F from September to June. Most of the heating season will be spent at temperatures where it's better to burn fossil fuels.

If you don't have access to natural gas, a propane furnace will only emit 6.3 kg of CO₂ per therm, or 210 grams per kWh.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

jpelder wrote: Wed Jul 21, 2021 2:45 pm That's a good point. IIRC, the number is more like 20 degrees F now, but Wisconsin will have many days well below that. But a heat pump will save OP a lot in spring and fall.
That's the temperature where the COP of American heat pumps gets down to 1. That's when heat pumps become as inefficient as electrical resistance heating.

However, the OP wants to "lessen carbon footprint." It's not enough for the COP to be above 1. The COP has to be 3.5 to offset the efficiency losses of electrical generation and the fuel mix of the power grid. Even the Asian mini-splits can't keep COP above 3.5 for most of the heating season in Wisconsin.

Wisconsin is a lot colder than North Carolina. The winter design temperature is 2°F in Milwaukee, -3°F in Madison, and -10° in Eau Claire. The calculations work out very differently in Wisconsin because so much time is spent below the efficient range of the heat pumps.
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Re: HVAC systems brands/electric heat pumps

Post by Mr. Rumples »

If you use it for heating, one thing to be sure of is how its going to function in snow and ice. Even here in VA, ice storms have deposited so much ice so fast that icicles formed and stopped the fan blades from spinning. That means you have to either go out in the bad weather and remove them or turn the system off. This past winter even with a 30 minute defrost cycle it could not keep up with the ice storm so while I was out there, others weren't and had their systems fail. I might build a shelter for it or I might just turn it off, cover it up and run on emergency until the storm abates, but that might not be an option up north.

The other consideration is the noise made when it goes into the defrost cycle. Its a very loud grinding noise on my Carrier unit; I'm surprised the neighbor hasn't complained.

The other thing is the air feels cold. It's coming out in the winter at less than skin temperature. Personally, if we had gas at my house, I would pay extra for the comfort.

In short, I really dislike a heat pump.
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Re: HVAC systems brands/electric heat pumps

Post by lthenderson »

brak wrote: Wed Jul 21, 2021 9:59 am Any suggestion about which brands are most efficient and reliable.
More important than brand quality is which brand is serviced in your area. I would much rather buy a unit from a local company that does quality installation and can get there fairly quickly if it stops working when really hot or cold than buy from a national name brand company that subcontracts out the installation with whomever isn't busy and is the cheapest and will put you on their waiting list if it ever needs serviced. There aren't a lot of moving parts in these systems to get a real quality difference between them.
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brak
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Re: HVAC systems brands/electric heat pumps

Post by brak »

Thank you everyone for great information. I really appreciate it.
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Re: HVAC systems brands/electric heat pumps

Post by WhyNotUs »

talzara wrote: Wed Jul 21, 2021 3:16 pm
That doesn't work in Wisconsin. You'll put less CO₂ into the atmosphere by heating your house with a gas furnace for most of the year.

Wisconsin gets 40% of its electricity from coal. The state's energy grid is so dirty that it puts out 630 grams of CO₂ per kWh. A natural gas furnace emits just 5.3 kg of CO₂ per therm, or 180 grams per kWh.

If you don't have access to natural gas, a propane furnace will only emit 6.3 kg of CO₂ per therm, or 210 grams per kWh.
[/quote]

Rather than going down the Rabbit hole of competing CO2/therm numbers (I am familiar with different and much higher numbers for gas and propane), I would encourage the OP to contact an experienced local contractor who sells and services cold climate heat pumps to perform the appropriate calculations for your home. For your own benefit, a energy assessment of your home is a great place to start in reducing your carbon imprint regardless of next steps.

I live in climate zone 6 and they are very effective here.
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Re: HVAC systems brands/electric heat pumps

Post by teCh0010 »

I leave someplace way warmer than WI, I went with a dual fuel heat pump. When it is above 40 outside the thermostat calls the heat pump for heat, when it is below 40 it calls the gas furnace. The gas furnace is the air handler for both modes, and is variable speed.

With your climate go dual fuel.
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Re: HVAC systems brands/electric heat pumps

Post by jabberwockOG »

Heat pumps work really well in Southern mild climates. We did have one really cold winter day a few years ago when the temp fell to 17F overnight. My heat pump ran 22 out of 24 hours on that day. For 2600 SQFT ranch, our electric bill in coldest month of winter runs apprx $120 (note we have electric hot water heater).

I would avoid heat pump in colder climates especially for places like Wisconsin, Illinois, etc.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

WhyNotUs wrote: Wed Jul 21, 2021 4:50 pm Rather than going down the Rabbit hole of competing CO2/therm numbers (I am familiar with different and much higher numbers for gas and propane), I would encourage the OP to contact an experienced local contractor who sells and services cold climate heat pumps to perform the appropriate calculations for your home.
CO₂ emissions per therm is a chemical constant for each fossil fuel. As long as there is complete combustion, it's always the same.

Since the OP wants to reduce CO₂ emissions, the heat pump should be compared to a 97% efficient furnace. The 3% of lost heat is offset by reduced electricity usage by the blower fan due to the higher temperature rise of a gas furnace.

Duct leakage would affect gas furnaces and ducted heat pumps equally. When comparing to a ductless heat pump, there are systems that can seal ducts from the inside.
WhyNotUs wrote: Wed Jul 21, 2021 4:50 pm For your own benefit, a energy assessment of your home is a great place to start in reducing your carbon imprint regardless of next steps.
The residential HVAC industry likes to sell equipment, but low-tech solutions like air-sealing and insulation can work just as well. Reducing heat loss by 20% has the same effect as improving equipment efficiency by 20%.
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Re: HVAC systems brands/electric heat pumps

Post by TomatoTomahto »

If you’d consider a GSHP (ground sourced heat pump, often called geothermal) as opposed to ASHP (air sourced HP), it will reduce your carbon footprint, running costs, and maintenance costs. A lot. But, you need sufficient land and the upfront costs are large.

We absolutely love our geothermal, year round, near Boston.

ETA: I see lots of references to COP on this thread. Our WaterFurnace GSHP has a COP of 5.1 and an EER of 43.5. Amazing what a difference it makes for a heat pump to operate at around 50 degrees.
Last edited by TomatoTomahto on Thu Jul 22, 2021 1:45 pm, edited 1 time in total.
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Re: HVAC systems brands/electric heat pumps

Post by brianH »

talzara wrote: Wed Jul 21, 2021 3:16 pm Wisconsin gets 40% of its electricity from coal. The state's energy grid is so dirty that it puts out 630 grams of CO₂ per kWh. A natural gas furnace emits just 5.3 kg of CO₂ per therm, or 180 grams per kWh.

A heat pump in Wisconsin has to achieve a COP of at least 3.5 to reduce CO₂ emissions compared to a natural gas furnace. Even the Asian mini-split heat pumps don't get above 3.5 until about 50°F.
Now, you need to factor the massive amount of in methane leaks (way worse for climate change than CO2) from NG infra: https://agupubs.onlinelibrary.wiley.com ... 19GL082635

It's also worth considering that a decision about what heat source to use now will probably last 15+ years. The grid across the country is rapidly shifting away from coal. In 15 years, the situation will look much different in WI.
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Re: HVAC systems brands/electric heat pumps

Post by firebirdparts »

If you want air conditioning, in my opinion you have no reason to avoid having the heat pump, as the added complexity and expense is trivial. Since you live in Wisconsin, you'll want a gas furnace too, and you should delete the 2nd stage electric heat. If you want, you can allow the thermostat to switch back and forth based on which is cheaper. Or, you can switch yourself. The simplistic view is that for a certain cost of gas and electricity, there is an outdoor temperature where you might as well shut the heat pump down. The temperature will be quite low if you just look for the temperature at which the cost per BTU is equal. Thermostats that would consider outdoor temperature to control two-stage heating have been around for 50 years that I know of. Maybe more. Anyway, not a new idea, nor complex. Like they say, do the math. Sometimes the jibber jabber and the math give different answers.

I don't know how much things have changed, but I have american standard here and the condensers are seamless. They wrapped the fins on. That is a pretty leak-proof design, and that's the most obvious. reliability improvement they have. They've performed admirably, but I do keep a spare capacitor around.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

brianH wrote: Thu Jul 22, 2021 12:28 pm Now, you need to factor the massive amount of in methane leaks (way worse for climate change than CO2) from NG infra: https://agupubs.onlinelibrary.wiley.com ... 19GL082635
That study was done in East Coast cities with iron pipes dating back as far as the 19th century. The OP lives in Wisconsin. We don't know the condition of the pipes.

I also gave the numbers for propane, which is delivered in trucks as a liquid. Burning propane emits about 18% more CO₂ per therm than natural gas, reducing the CO₂ breakeven COP to 3.0. In Wisconsin's climate, that only gives you a couple more weeks of heat pump operation before propane becomes cleaner.

It doesn't make financial sense to burn propane if natural gas is available, but it would reduce emissions if the natural gas pipes are leaky enough. It doesn't make financial sense to run heat pumps if natural gas is available, either. Wisconsin pays about 15 cents per kWh for electricity and 80 cents per therm for natural gas (2.7 cents per kWh). The only reason this thread exists is because the OP asked how to reduce CO₂ emissions from heating.
brianH wrote: Thu Jul 22, 2021 12:28 pm It's also worth considering that a decision about what heat source to use now will probably last 15+ years. The grid across the country is rapidly shifting away from coal. In 15 years, the situation will look much different in WI.
Most homeowners who install a heat pump will start using it right away. They will not keep it turned off for 15 years as they wait for electricity generation to become cleaner.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

TomatoTomahto wrote: Thu Jul 22, 2021 12:00 pm ETA: I see lots of references to COP on this thread. Our WaterFurnace GSHP has a COP of 5.1 and an EER of 43.5. Amazing what a difference it makes for a heat pump to operate at around 50 degrees.
Air-source heat pumps specify a COP that includes the electricity used by the fan on the outside unit.

Ground-source heat pumps usually specify the COP of just the heat pump, without adding in the electricity used to pump water through the system. That number depends on the exact setup of the ground loop, which the equipment manufacturer cannot control.

If your ground source heat pump specifies a COP of 5.1, your system COP is probably around 4.
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Re: HVAC systems brands/electric heat pumps

Post by Scotttheking »

wfrobinette wrote: Wed Jul 21, 2021 2:09 pm
brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.

Cold weather heat pumps are 100% to -15 now.
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Re: HVAC systems brands/electric heat pumps

Post by vg55 »

At this moment, I am in the very same position. Two air handlers and two compressors on their last legs.

I live in CT and investigated multiple options:

[*] do nothing -- run to failure and risk marital status
[*] replace air handlers and air compressors with 16 SEER and more efficient systems ($16,000)
[*] replace air handlers and install new air source heat pumps -- leave oil boiler in place as backup ($27,000);
[*] replace oil boiler with geothermal system -- drilling / trenching a no go on this small lot

p.s. no subsidies available since i couldn't meet SEER and HSPF requirements

I opted for the 16K solution.
[*] First Company model 30 HBXB 2 ½ - ton R410A hi-eff air handler.
[*] First Company model 36 HBXB 3-ton R410A hi-eff air handler. (2nd floor unit)
[*] 16 SEER air conditioning equipment model Heil NXA630GKA
[*] 16 SEER air conditioning equipment model Heil NXA636GKA

It's a lot of money for 60 days of air conditioning a year for 15 years; but I expect to sell this house before in 10 years or less.
most buyers in this area expect central air conditioning. grew up in a house with an attic fan. worked great for the time.
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Re: HVAC systems brands/electric heat pumps

Post by vg55 »

PS. I used this site to obtain technical data on matched and mixed systems.

https://www.ahridirectory.org/NewSearch ... ypeId=3523

AHRI -- for certified product performance. Eversource subsidy programs required AHRI certificates.
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Re: HVAC systems brands/electric heat pumps

Post by 4nursebee »

How does one know when a system is on its last legs?
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vg55
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Re: HVAC systems brands/electric heat pumps

Post by vg55 »

past warranty;
coils freezing;
needing annual repair @ $1k
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Re: HVAC systems brands/electric heat pumps

Post by TexasPE »

galawdawg wrote: Wed Jul 21, 2021 10:16 am ...a ten (10) year parts AND labor warranty...
+1 The above saved me close to 5 figures on AC repair bills for our two systems .Evaporator-coil design flaws :oops: required two replacements on each system. In addition, during the first 10 years of ownership company also replaced a compressor and air handler under warranty. No problems with the furnaces, though :D
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Re: HVAC systems brands/electric heat pumps

Post by adamthesmythe »

Scotttheking wrote: Fri Jul 23, 2021 12:39 pm
wfrobinette wrote: Wed Jul 21, 2021 2:09 pm
brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.

Cold weather heat pumps are 100% to -15 now.
I'd like to understand this more. Thermodynamically the heat output of a heat pump decreases as the outdoor temperature decreases. Bu the heat demand increases as the outdoor temperature goes down.

Does that mean that the heat pump has to be sized for the worst case? Then it will be oversized for more ordinary conditions. Are there consequences of having an oversized heat pump?
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Re: HVAC systems brands/electric heat pumps

Post by jharkin »

wfrobinette wrote: Wed Jul 21, 2021 2:09 pm
brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.
Things have changed significantly… this is not even remotely true today.

I’m getting quotes for replacing one of my central ACs. Mitsubishi standard unit is SEER18/ HSPF13 and in heat pump mode ranges from 4.2 COP@47 down to “only” 3.5 COP@17F.

The Mitsubishi hyper heats are a little less efficient but maintain full output to -5F and partial output to -15F.


And this is their ducted systems. The mini splits are even better.
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Re: HVAC systems brands/electric heat pumps

Post by jharkin »

adamthesmythe wrote: Fri Jul 23, 2021 4:37 pm
Scotttheking wrote: Fri Jul 23, 2021 12:39 pm
wfrobinette wrote: Wed Jul 21, 2021 2:09 pm
brak wrote: Wed Jul 21, 2021 9:59 am My HVAC air conditioner is on its last legs. Any suggestion about which brands are most efficient and reliable. Also, I'm from Wisconsin but I am considering purchasing an electric heat pump system instead to lessen carbon footprint. Anyone have any experience with such a system? Pros and cons, things to consider? Thanks.
Heat pump is NOT very efficient below 32 degrees F. But it will handled spring summer and fall nicely up there. Look at a dual fuel system.

Cold weather heat pumps are 100% to -15 now.
I'd like to understand this more. Thermodynamically the heat output of a heat pump decreases as the outdoor temperature decreases. Bu the heat demand increases as the outdoor temperature goes down.

Does that mean that the heat pump has to be sized for the worst case? Then it will be oversized for more ordinary conditions. Are there consequences of having an oversized heat pump?
All heating systems are sized for “worst case” This is called the design day temp and is spelled out in ASHRAE manuals.

The beauty of these modern systems is that they modulate with multi stage compressors and variable speed blowers and can adjust to the load. The days of “bang bang” full blast to off or full blast systems is long gone…

Any installer that tells you “more than 16 seer” is not worth it is just afraid of the technology and is robbing you of the benefits of the best new systems.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

jharkin wrote: Fri Jul 23, 2021 4:53 pm I’m getting quotes for replacing one of my central ACs. Mitsubishi standard unit is SEER18/ HSPF13 and in heat pump mode ranges from 4.2 COP@47 down to “only” 3.5 COP@17F.

The Mitsubishi hyper heats are a little less efficient but maintain full output to -5F and partial output to -15F.
Mitsubishi rates its heat pumps for unrealistic conditions. You are unlikely to achieve the rated COP.

In 2015, the DOE commissioned a test of Fujitsu and Mitsubishi heat pumps in several real houses. Performance was found to fall short of specifications.
For the Mitsubishi FE18:
  • At 47°F, specified COP was 4.11. Measured COP was 2.2, 3.5, and 2.6.
  • At 17°F, specified COP was 2.77. Measured COP was 1.5, 2.2, and 1.7.
For the Mitsubishi FE12, no COP is specified. Mitsubishi gives rated capacity and input, which can be used to calculate COP.
  • At 47°F, rated COP was 4.2. Measured COP was 2.5, 1.3, and 2.6.
  • At 17°F, rated COP was 3.0. Measured COP was 1.7, 1.0, and 1.7.
Mitsubishi is measuring the COP at the optimal capacity for each temperature. For example, the FE18 is rated at 21,600 BTU/h at 47°F, but it's rated at 11,700 BTU/h at 17°F. This is highly unrealistic since it assumes that you will use less heat at lower temperatures. You actually need more heat when it's cold outside, so you won't be operating the heat pump at its optimal capacity.

Mitsubishi is also calculating the COP of only the outside unit, without taking into account the of the inside unit. This is reasonable when comparing to another heat pump, but it's not reasonable when comparing to a furnace. A combustion furnace has a much higher temperature rise, so the blower fan can deliver the same heat while moving less air.

The capacity ratings can be trusted because homeowners will complain if their houses are cold after installing heat pumps. However, nobody measures the COP that they're getting, so Mitsubishi can get away with overstating the COP.
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Re: HVAC systems brands/electric heat pumps

Post by talzara »

adamthesmythe wrote: Fri Jul 23, 2021 4:37 pm I'd like to understand this more. Thermodynamically the heat output of a heat pump decreases as the outdoor temperature decreases. Bu the heat demand increases as the outdoor temperature goes down.

Does that mean that the heat pump has to be sized for the worst case? Then it will be oversized for more ordinary conditions. Are there consequences of having an oversized heat pump?
American heat pump manufacturers usually specify capacity at 47°F and deliver less than 100% of capacity at lower temperatures. They design them as air conditioners first, and they just run them in reverse for heating.

Asian heat pump manufacturers usually specify capacity at -15°F to 5°F and deliver greater than 100% of capacity at higher temperatures. They design them for heating first, and they run them in reverse for air conditioning. Since this makes them oversized for cooling, Asian mini-splits usually come with inverter-driven compressors so they can ramp down their capacity in summer.
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