Furnace Issues

Questions on how we spend our money and our time - consumer goods and services, home and vehicle, leisure and recreational activities
Post Reply
AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Furnace Issues

Post by AD3 » Tue Nov 07, 2017 12:27 am

Hello everyone,

I have a 28 year old furnace that has been having issues with the fan starting up. My furance works sporadically, there are times when the unit works without any problems, and there are times when I start my heater and all I hear is noise. I wanted to see if anyone else has had a similar problem with their furnace.

I usually set my thermostat to 70 degrees, when it turns on sometimes my unit makes a humming noise, other times it starts up and heat is felt throughout the house. I recently replaced my capacitor, which did not fix my issues, currently looking at whether the fan relay might be an issue.

I've thought about replacing it and I have looked into that, a new furnace would run me $3,500 but as long as the furnace still works I thought I could do little repairs until the unit no longer works.

If anyone has any tips or suggestions, thank you in advance.

AD3

User avatar
ClevrChico
Posts: 1316
Joined: Tue Apr 03, 2012 8:24 pm

Re: Furnace Issues

Post by ClevrChico » Tue Nov 07, 2017 12:58 am

I had similar issues when the utility company wasn't providing enough voltage to the house. If I was drawing other load in the house, there wouldn't be enough voltage for the igniter to get hot enough. The utility company refused to come to the house without a request from a licensed electrician. The electrician thought I was crazy when I told him about the suspected voltage problem, but he reluctantly tested it, and then agreed with me. When the linemen arrived and discovered the utility problem, they were completely on my side and couldn't believe the utility company wouldn't help me initially. Some components on the line had actually melted due to under rated wiring. That could be a tricky one to get resolved. I don' t think an average tech would have found a root cause.

If your furnace is having a sensor problem or if a fault is detected, it should eventually go into lockout mode, and have to be manually power cycled before it will attempt to start again. If it's bad enough, it can hard lockout. A service call by very good technician shouldn't be too expensive. It sounds like it's time to have it looked at.

Also, with possible rebates and higher efficiency, return on a new furnace can be very short. 28 years is a good run.
Last edited by ClevrChico on Tue Nov 07, 2017 1:05 am, edited 1 time in total.

User avatar
Sandtrap
Posts: 5500
Joined: Sat Nov 26, 2016 6:32 pm
Location: Hawaii😀 Northern AZ.😳 Retired.

Re: Furnace Issues

Post by Sandtrap » Tue Nov 07, 2017 1:05 am

Newer furnaces are more energy efficient, heat better and faster, and are quieter.
Maybe time to upgrade? :D

Chip
Posts: 2377
Joined: Wed Feb 21, 2007 4:57 am

Re: Furnace Issues

Post by Chip » Tue Nov 07, 2017 3:51 am

I have a gas furnace of a similar age. It's a Trane 80XL.

The usual startup sequence for mine is that first the inducer blower starts up. It's a small blower that creates a slight negative pressure ("induced draft") in the combustion chamber. After a few seconds of run time, IF a sensor determines that there is sufficient negative pressure, a relay clicks and the hot surface ignitor begins heating. After about 10 more seconds the gas valve opens and the furnace lights. IF the combustion sensor sees that it did in fact light, after ~30 more seconds the main circulating fan starts.

Most of those steps make specific noises that I am used to hearing, so I can tell where the furnace is in the startup process. Are you familiar with the noises from your furnace? That might give you a clue.

The hum you hear MAY be the inducer blower. If the induced draft sensor doesn't read sufficient draft, the inducer blower will continue to run for a long time but the furnace will never start. That happened with my furnace a several years ago. It turned out that the tube from the induced draft sensor to the combustion chamber was clogged with rust, preventing the ID sensor from measuring the draft correctly. Once I cleaned out that tube the furnace began working again.

I am not saying that's the problem with your furnace. It's just what happened with mine.

As I'm sure you know, there are inherent dangers in working on a gas furnace, like blowing your house and yourself into little pieces. If you aren't sure about what you're doing, call a certified technician.

denovo
Posts: 4384
Joined: Sun Oct 13, 2013 1:04 pm

Re: Furnace Issues

Post by denovo » Tue Nov 07, 2017 5:42 am

AD3 wrote:
Tue Nov 07, 2017 12:27 am
Hello everyone,


I've thought about replacing it and I have looked into that, a new furnace would run me $3,500 but as long as the furnace still works I thought I could do little repairs until the unit no longer works.

If anyone has any tips or suggestions, thank you in advance.

AD3
A 28 year furnace is due for retirement. It's dying and sporadically working. Don't just think about the upfront cost. There are rebates. You will save in energy efficiency. Winter is coming (unless you live down under). It's time to say goodbye to your furnace.
"Don't trust everything you read on the Internet"- Abraham Lincoln

Prudence
Posts: 396
Joined: Fri Mar 09, 2012 4:55 pm

Re: Furnace Issues

Post by Prudence » Tue Nov 07, 2017 8:30 am

AD3 wrote:
Tue Nov 07, 2017 12:27 am
Hello everyone,

I have a 28 year old furnace that has been having issues with the fan starting up. My furance works sporadically, there are times when the unit works without any problems, and there are times when I start my heater and all I hear is noise. I wanted to see if anyone else has had a similar problem with their furnace.

I usually set my thermostat to 70 degrees, when it turns on sometimes my unit makes a humming noise, other times it starts up and heat is felt throughout the house. I recently replaced my capacitor, which did not fix my issues, currently looking at whether the fan relay might be an issue.

I've thought about replacing it and I have looked into that, a new furnace would run me $3,500 but as long as the furnace still works I thought I could do little repairs until the unit no longer works.

If anyone has any tips or suggestions, thank you in advance.

AD3
My gas furnace ignitor (ignites the burners) wore out last Thursday so it was replaced for $176.00. We have a maintenance agreement with a local HVAC company which has been a good thing.

adamthesmythe
Posts: 2335
Joined: Mon Sep 22, 2014 4:47 pm

Re: Furnace Issues

Post by adamthesmythe » Tue Nov 07, 2017 10:04 am

1. Unless I missed it, you don't actually say what kind of furnace you have. I assume gas.

2. There are several things that can cause intermittent ignition. One of the other posters has described the sequence of events when starting a gas furnace.

3. Unless you really really want to figure out the operation of modern gas furnaces, get a furnace guy to come in for troubleshooting. The only reason you absolutely have to replace a furnace is for exhaust or water leaks.

Personally I have done troubleshooting of systems much more complex than a gas furnace, but I still hire a furnace guy to maintain and fix them. They got the knowledge, they got the tools, and they got the parts.

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Tue Nov 07, 2017 10:19 am

adamthesmythe wrote:
Tue Nov 07, 2017 10:04 am
1. Unless I missed it, you don't actually say what kind of furnace you have. I assume gas.

2. There are several things that can cause intermittent ignition. One of the other posters has described the sequence of events when starting a gas furnace.

3. Unless you really really want to figure out the operation of modern gas furnaces, get a furnace guy to come in for troubleshooting. The only reason you absolutely have to replace a furnace is for exhaust or water leaks.

Personally I have done troubleshooting of systems much more complex than a gas furnace, but I still hire a furnace guy to maintain and fix them. They got the knowledge, they got the tools, and they got the parts.
Safety. Carbon monoxide leaks are a silent and deadly risk and fatal at very low concentrations. Don't even begin to think about slow gas leaks and explosions.

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Tue Nov 07, 2017 10:24 am

AD3 wrote:
Tue Nov 07, 2017 12:27 am
Hello everyone,

I have a 28 year old furnace that has been having issues with the fan starting up. My furance works sporadically, there are times when the unit works without any problems, and there are times when I start my heater and all I hear is noise. I wanted to see if anyone else has had a similar problem with their furnace.

I usually set my thermostat to 70 degrees, when it turns on sometimes my unit makes a humming noise, other times it starts up and heat is felt throughout the house. I recently replaced my capacitor, which did not fix my issues, currently looking at whether the fan relay might be an issue.

I've thought about replacing it and I have looked into that, a new furnace would run me $3,500 but as long as the furnace still works I thought I could do little repairs until the unit no longer works.

If anyone has any tips or suggestions, thank you in advance.

AD3
You can guesstimate that a new furnace would save you around 20% on your gas bill-- modern furnaces (gas) run efficiencies of over 90% and yours is probably doing around 70%-- it might even be possible to look that up (Energy Information Agency has a calculator on one of its web pages).

So: how long do you plan to be in the house? Because you can work out a years to payback with the conservative assumption that retail gas bills stay flat. If you live in New England, which has high retail gas prices and cold winters, you should get quite a quick payback.

If you sell the house the cost of a new furnace probably gets worked into the sale price BUT it's always hard to figure out whether that is actually happening because it gets lost in other things (like the costs of redecorating and a new kitchen).

I would say if you plan to be in the house another 5 years or less it's not worth doing if you can get this thing over the line. More than that, it might well be worth doing.

My parents had been planning to move in another 5 years for the last 30 years or so- -and are now on the 58th year in the house ;-).

Jack FFR1846
Posts: 8122
Joined: Tue Dec 31, 2013 7:05 am

Re: Furnace Issues

Post by Jack FFR1846 » Tue Nov 07, 2017 10:32 am

So I'm going to assume it's an oil furnace, since it seems from this thread that you might be in New England. First, is the oil tank at a reasonable level? Has the oil been filled at a time where it could have gone below level?

If you don't know, get an old plastic bowl. There's a starter button on the burner unit and near where the oil line comes into the unit, there's a valve and outlet nipple. You're going to hit the button and turn the nipple (probably a 10mm or smaller wrench) and oil will go into the bowl below. If you get a bunch of spitting or clearly oil with air mixed, do this several times until the oil flows clearly as just fluid. Each cycle, push the button and open the valve for about 5 seconds then close. Then try again.

Or you can call the oil company and tell them your furnace isn't working and they'll come and fix it.
Bogle: Smart Beta is stupid

neilpilot
Posts: 1928
Joined: Fri Dec 04, 2015 1:46 pm
Location: Memphis area

Re: Furnace Issues

Post by neilpilot » Tue Nov 07, 2017 10:37 am

Jack FFR1846 wrote:
Tue Nov 07, 2017 10:32 am
So I'm going to assume it's an oil furnace, since it seems from this thread that you might be in New England.

Not saying your wrong, but what in the OP's text lead to your assumptions? Did you know that OP3 has a car registered in California?

AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Re: Furnace Issues

Post by AD3 » Tue Nov 07, 2017 11:41 am

ClevrChico wrote:
Tue Nov 07, 2017 12:58 am
I had similar issues when the utility company wasn't providing enough voltage to the house. If I was drawing other load in the house, there wouldn't be enough voltage for the igniter to get hot enough. The utility company refused to come to the house without a request from a licensed electrician. The electrician thought I was crazy when I told him about the suspected voltage problem, but he reluctantly tested it, and then agreed with me. When the linemen arrived and discovered the utility problem, they were completely on my side and couldn't believe the utility company wouldn't help me initially. Some components on the line had actually melted due to under rated wiring. That could be a tricky one to get resolved. I don' t think an average tech would have found a root cause.

If your furnace is having a sensor problem or if a fault is detected, it should eventually go into lockout mode, and have to be manually power cycled before it will attempt to start again. If it's bad enough, it can hard lockout. A service call by very good technician shouldn't be too expensive. It sounds like it's time to have it looked at.

Also, with possible rebates and higher efficiency, return on a new furnace can be very short. 28 years is a good run.
That's a troubling issue, I'll most likely call a tech to see if its worth buying a new furance. 28 years was a good run.

AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Re: Furnace Issues

Post by AD3 » Tue Nov 07, 2017 11:46 am

Chip wrote:
Tue Nov 07, 2017 3:51 am
I have a gas furnace of a similar age. It's a Trane 80XL.

The usual startup sequence for mine is that first the inducer blower starts up. It's a small blower that creates a slight negative pressure ("induced draft") in the combustion chamber. After a few seconds of run time, IF a sensor determines that there is sufficient negative pressure, a relay clicks and the hot surface ignitor begins heating. After about 10 more seconds the gas valve opens and the furnace lights. IF the combustion sensor sees that it did in fact light, after ~30 more seconds the main circulating fan starts.

Most of those steps make specific noises that I am used to hearing, so I can tell where the furnace is in the startup process. Are you familiar with the noises from your furnace? That might give you a clue.

The hum you hear MAY be the inducer blower. If the induced draft sensor doesn't read sufficient draft, the inducer blower will continue to run for a long time but the furnace will never start. That happened with my furnace a several years ago. It turned out that the tube from the induced draft sensor to the combustion chamber was clogged with rust, preventing the ID sensor from measuring the draft correctly. Once I cleaned out that tube the furnace began working again.

I am not saying that's the problem with your furnace. It's just what happened with mine.

As I'm sure you know, there are inherent dangers in working on a gas furnace, like blowing your house and yourself into little pieces. If you aren't sure about what you're doing, call a certified technician.
"The hum you hear MAY be the inducer blower. If the induced draft sensor doesn't read sufficient draft, the inducer blower will continue to run for a long time but the furnace will never start. That happened with my furnace a several years ago. It turned out that the tube from the induced draft sensor to the combustion chamber was clogged with rust, preventing the ID sensor from measuring the draft correctly. Once I cleaned out that tube the furnace began working again."

This sounds very similar to issue that I think my furnace is having, I also have a (gas) Rheem 80Plus furance. Calling a certified technician was my next step in this process.

AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Re: Furnace Issues

Post by AD3 » Tue Nov 07, 2017 11:47 am

adamthesmythe wrote:
Tue Nov 07, 2017 10:04 am
1. Unless I missed it, you don't actually say what kind of furnace you have. I assume gas.

2. There are several things that can cause intermittent ignition. One of the other posters has described the sequence of events when starting a gas furnace.

3. Unless you really really want to figure out the operation of modern gas furnaces, get a furnace guy to come in for troubleshooting. The only reason you absolutely have to replace a furnace is for exhaust or water leaks.

Personally I have done troubleshooting of systems much more complex than a gas furnace, but I still hire a furnace guy to maintain and fix them. They got the knowledge, they got the tools, and they got the parts.
I have a (gas) Rheem 80Plus furance. Thanks for the advice. :sharebeer

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Tue Nov 07, 2017 11:51 am

neilpilot wrote:
Tue Nov 07, 2017 10:37 am
Jack FFR1846 wrote:
Tue Nov 07, 2017 10:32 am
So I'm going to assume it's an oil furnace, since it seems from this thread that you might be in New England.

Not saying your wrong, but what in the OP's text lead to your assumptions? Did you know that OP3 has a car registered in California?
I think it tracks back to my sentence "If you live in New England then [new furnace] can have quite a fast payback [because gas prices are high]"

This is how rumours get started ;-).

BoardMan
Posts: 11
Joined: Wed Dec 08, 2010 12:17 pm

Re: Furnace Issues

Post by BoardMan » Tue Nov 07, 2017 11:52 am

Most 80% efficient furnaces don't have an induction motor. Have you confirmed the blower motor capacitor is okay?

AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Re: Furnace Issues

Post by AD3 » Tue Nov 07, 2017 11:53 am

Valuethinker wrote:
Tue Nov 07, 2017 10:24 am
AD3 wrote:
Tue Nov 07, 2017 12:27 am
Hello everyone,

I have a 28 year old furnace that has been having issues with the fan starting up. My furance works sporadically, there are times when the unit works without any problems, and there are times when I start my heater and all I hear is noise. I wanted to see if anyone else has had a similar problem with their furnace.

I usually set my thermostat to 70 degrees, when it turns on sometimes my unit makes a humming noise, other times it starts up and heat is felt throughout the house. I recently replaced my capacitor, which did not fix my issues, currently looking at whether the fan relay might be an issue.

I've thought about replacing it and I have looked into that, a new furnace would run me $3,500 but as long as the furnace still works I thought I could do little repairs until the unit no longer works.

If anyone has any tips or suggestions, thank you in advance.

AD3
You can guesstimate that a new furnace would save you around 20% on your gas bill-- modern furnaces (gas) run efficiencies of over 90% and yours is probably doing around 70%-- it might even be possible to look that up (Energy Information Agency has a calculator on one of its web pages).

So: how long do you plan to be in the house? Because you can work out a years to payback with the conservative assumption that retail gas bills stay flat. If you live in New England, which has high retail gas prices and cold winters, you should get quite a quick payback.

If you sell the house the cost of a new furnace probably gets worked into the sale price BUT it's always hard to figure out whether that is actually happening because it gets lost in other things (like the costs of redecorating and a new kitchen).

I would say if you plan to be in the house another 5 years or less it's not worth doing if you can get this thing over the line. More than that, it might well be worth doing.

My parents had been planning to move in another 5 years for the last 30 years or so- -and are now on the 58th year in the house ;-).
I live in the Bay Area, California so the weather doesn't get all that bad here. We use a furnace maybe 4 months throughout the year. Gas bill is somewhat cheap, I don't plan to sell my house, but I might rent it out in the future.

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Tue Nov 07, 2017 11:55 am

AD3 wrote:
Tue Nov 07, 2017 11:47 am
adamthesmythe wrote:
Tue Nov 07, 2017 10:04 am
1. Unless I missed it, you don't actually say what kind of furnace you have. I assume gas.

2. There are several things that can cause intermittent ignition. One of the other posters has described the sequence of events when starting a gas furnace.

3. Unless you really really want to figure out the operation of modern gas furnaces, get a furnace guy to come in for troubleshooting. The only reason you absolutely have to replace a furnace is for exhaust or water leaks.

Personally I have done troubleshooting of systems much more complex than a gas furnace, but I still hire a furnace guy to maintain and fix them. They got the knowledge, they got the tools, and they got the parts.
I have a (gas) Rheem 80Plus furance. Thanks for the advice. :sharebeer
http://yaunco.com/pdfs/rheem/heating/rgpn_spec.pdf

based on that you have an 80% efficiency. New ones would be c. 95% so you *should* get a 1/6th reduction in fuel bills.

2 big assumptions:

- yours is still doing 80% efficiency
- the new ones get the rated efficiency (I suspect they only do so for long runs, where the condenser works well)

It's probably best to assume that you will get say a 12.5% improvement in gas consumption (assuming the datasheet above is the correct one for your model). That's an on the safe side assumption.

AD3
Posts: 23
Joined: Tue Apr 04, 2017 11:05 pm

Re: Furnace Issues

Post by AD3 » Tue Nov 07, 2017 11:59 am

Jack FFR1846 wrote:
Tue Nov 07, 2017 10:32 am
So I'm going to assume it's an oil furnace, since it seems from this thread that you might be in New England. First, is the oil tank at a reasonable level? Has the oil been filled at a time where it could have gone below level?

If you don't know, get an old plastic bowl. There's a starter button on the burner unit and near where the oil line comes into the unit, there's a valve and outlet nipple. You're going to hit the button and turn the nipple (probably a 10mm or smaller wrench) and oil will go into the bowl below. If you get a bunch of spitting or clearly oil with air mixed, do this several times until the oil flows clearly as just fluid. Each cycle, push the button and open the valve for about 5 seconds then close. Then try again.

Or you can call the oil company and tell them your furnace isn't working and they'll come and fix it.
I called the gas company last year to check the furance and water heater, they told me the issue might be the capacitor, which is what I changed but that hasn't fixed my problem. So I'll have to call a tech to give me a diagnoses on the furance.

Dudley
Posts: 103
Joined: Tue May 09, 2017 5:34 am

Re: Furnace Issues

Post by Dudley » Tue Nov 07, 2017 11:59 am

Upgrade your AC to a heat pump ?

bloom2708
Posts: 5015
Joined: Wed Apr 02, 2014 2:08 pm
Location: Fargo, ND

Re: Furnace Issues

Post by bloom2708 » Tue Nov 07, 2017 12:03 pm

Do you have the manual or can you find it online?

Turn the furnace off, turn it on and have the thermostat set so it will draw heat. When the start up goes through the steps, there should be a flashing light that if something fails, blinks quickly or in a pattern.

You find the pattern and then cross reference with the manual. This tells you what is going on. The furnace might be too old to have that troubleshooting feature.

If that doesn't help, get a local heating company out to diagnose. At 28 years, you can continue to limp along. A new system would be much more efficient, but it will cost to install.
"We are not here to please, but to provoke thoughtfulness." --Unknown Boglehead

likegarden
Posts: 2713
Joined: Mon Feb 26, 2007 5:33 pm

Re: Furnace Issues

Post by likegarden » Tue Nov 07, 2017 2:47 pm

I had a 39 year old furnace, and a technician said it needs some work, so I bought a new furnace. The new furnace is more efficient, and probably will last a long time.

Fox
Posts: 40
Joined: Tue Dec 13, 2016 2:00 pm

Re: Furnace Issues

Post by Fox » Tue Nov 07, 2017 3:08 pm

We recently had similar furnace troubles which ended up being an easy repair.

Our furnace is about 15 years old and was turning on and running, but no heat was being produced. It was giving an error code that listed a number of possible problems including blocked intake or exhaust, failing inducer motor, etc etc.

It turned out that there was a blockage in the water trap that drains condensation from the unit, which was causing a switch to not open and allow the gas to ignite. Repair cost was 30 minutes of labor plus the service call from a local, family owned HVAC company.

Good luck.

Chip
Posts: 2377
Joined: Wed Feb 21, 2007 4:57 am

Re: Furnace Issues

Post by Chip » Tue Nov 07, 2017 4:48 pm

Valuethinker wrote:
Tue Nov 07, 2017 10:24 am
You can guesstimate that a new furnace would save you around 20% on your gas bill-- modern furnaces (gas) run efficiencies of over 90% and yours is probably doing around 70%-- it might even be possible to look that up (Energy Information Agency has a calculator on one of its web pages).
[...]
I would say if you plan to be in the house another 5 years or less it's not worth doing if you can get this thing over the line. More than that, it might well be worth doing.
Some actual potential savings numbers. As I mentioned above I have an 80% efficient gas furnace similar to the OP's. I live in an area with relatively cheap gas (currently $.52/CCF). A normal winter is about 5000 degree-days and I use 800 CCF (I have subtracted out usage from water heating, gas fireplace and gas grill). So I spend $416/year on gas heating. If I were to buy a new 95% furnace I would be spending $350 instead, for a savings of $66/year.

Not a quick payout for me. Obviously I will eventually replace the furnace, but saving $ on gas won't be the reason.

User avatar
cockersx3
Posts: 193
Joined: Sun Apr 17, 2016 3:55 pm

Re: Furnace Issues

Post by cockersx3 » Tue Nov 07, 2017 8:59 pm

Recommend that you just find a local HVAC guy that will come out and perform a diagnosis for a fixed fee, and see if he can ID the problem. I'm all for DIY where I can, but for $100-200 having someone take a look and definitively tell you what's wrong with it would be worth it.

I did that recently with a similar issue with my system (circ fan with intermittent issues), and the guy told me that the motherboard on my 20yr old unit was shot. He also temporarily hard-wired the incoming 120VAC power to the fan to force it to be on all the time, rather than routing the power through the furnace motherboard which wasn't working.

However, be prepared to do the fix yourself if the cost the HVAC tech proposes is too much. In the case above, the guy proceeded to quote me like NINE HUNDRED DOLLARS to replace the darn thing (!!!), at which point he tried to sell me on a new system. We agreed to have him get some quotes ad get back to me. But the second he left, I looked up my motherboard online (via the model numbers on the board) and found a replacement for like $80 or so. Took like 30 mins total to replace it. Unbelievable...!

User avatar
Watty
Posts: 14631
Joined: Wed Oct 10, 2007 3:55 pm

Re: Furnace Issues

Post by Watty » Tue Nov 07, 2017 11:41 pm

One huge advantage of replacing your furnace now is that you can take your time and get several bids to get a good price. If you wait until it dies you could be in a situation where you have to replace it in a hurry. A lot depends on your budget but I tend to replace things like that before they totally die and have to be replaced.

If you use AC much of the year and it is old too then you might want to consider getting that replaced at the same time since they there may be some costs savings with installing them both at the same time. In addition to efficiency many of the new furnaces and AC systems have options to run at different speeds and also monitor the humidity to make the house feel a lot more comfortable. I replaced both my furnace and AC at the same time a few years ago with mid-range systems and the house is noticeably more comfortable now.
Last edited by Watty on Tue Nov 07, 2017 11:50 pm, edited 1 time in total.

User avatar
jabberwockOG
Posts: 1513
Joined: Thu May 28, 2015 7:23 am

Re: Furnace Issues

Post by jabberwockOG » Tue Nov 07, 2017 11:46 pm

28 years is a good long service life. I'd get three bids and replace it with a newer more efficient model, particularly if it is a gas furnace.

2comma
Posts: 1241
Joined: Thu Jul 15, 2010 11:37 pm

Re: Furnace Issues

Post by 2comma » Wed Nov 08, 2017 12:35 am

cockersx3 wrote:
Tue Nov 07, 2017 8:59 pm
Recommend that you just find a local HVAC guy that will come out and perform a diagnosis for a fixed fee, and see if he can ID the problem. I'm all for DIY where I can, but for $100-200 having someone take a look and definitively tell you what's wrong with it would be worth it.

I did that recently with a similar issue with my system (circ fan with intermittent issues), and the guy told me that the motherboard on my 20yr old unit was shot. He also temporarily hard-wired the incoming 120VAC power to the fan to force it to be on all the time, rather than routing the power through the furnace motherboard which wasn't working.

However, be prepared to do the fix yourself if the cost the HVAC tech proposes is too much. In the case above, the guy proceeded to quote me like NINE HUNDRED DOLLARS to replace the darn thing (!!!), at which point he tried to sell me on a new system. We agreed to have him get some quotes ad get back to me. But the second he left, I looked up my motherboard online (via the model numbers on the board) and found a replacement for like $80 or so. Took like 30 mins total to replace it. Unbelievable...!
I recently got interested in figuring out what I could easily DIY on our AC. This was not to save money but sometimes it fails at the worst time and it can take longer than I want to get someone to the house. By watching HVAC videos on youtube I learned several things.

- The capacitor and the contactor on an AC are the two most common problems - I now stock both which only cost me $30 and I can replace either in 10 minutes or less.
- The furnace is not terribly difficult to diagnose. All you need is a multi meter and a little help from youtube. The parts can be sourced online and aren't expensive. No problem letting a tech fix it but just be aware some are very inclined to convince you to replace your system. If they do suggest that at least you know why.
- The main worry with a furnace is if the combustion chamber has cracks or burn thru. This lets CO be blown into the home. This is why it is a good idea to have the furnace cleaned and inspected, once a year if it is older.
- Small companies (single owner or father/son) are probably the best place to find someone that is willing to diagnose and fix older systems. Some companies specialize in repairs, others prefer to replace. I recently used a larger company - the older tech told me he didn't want to work for a company that pushed selling - then he proceeded to try to tell me my 12 year old system was too old, R22 was going to be the end of it, their over priced annual contract would solve the R22 issue (Not, 1 free pound of freon). I was looking for a part locally, I called what I thought was a parts distributor, turned out to be a small local business that sold parts on the side. He encouraged me to run a few checks, he said he was off to do an install but I could pickup my part in his mailbox, just leave $10 in return. If I had any questions to call him, guess who will be installing my new HVAC system when the time comes?
If I am stupid I will pay.

fishboat
Posts: 494
Joined: Tue Oct 14, 2014 12:15 pm

Re: Furnace Issues

Post by fishboat » Wed Nov 08, 2017 9:55 am

Chip wrote:
Tue Nov 07, 2017 4:48 pm
...for a savings of $66/year.

Not a quick payout for me. Obviously I will eventually replace the furnace, but saving $ on gas won't be the reason.
This has been my experience also. I had an 18 year-old Lennox Pulse that needed a new board..board wasn't available as Lennox abandoned supporting the furnace due to a design flaw-recall...so I was stuck getting a new furnace. The installer offered a new Lennox as an option..I declined and chose another brand.

The new one(~$3200) has much higher efficiency..claimed at least..but, honestly, I don't see any difference in gas usage. I live in Wisconsin and burn propane for heat...not cheap compared to NG. Granted, I don't track the gas usage/cost really close, but the before after running costs are anything but dramatic(20%..). Be wary of efficiency claims..how is that efficiency number determined vs how was it determined 28 years ago. If there's a difference, then the new efficiency number is meaningless.

Example..look to shop vacs. You can buy a "5 peak-hp" shop vacuum that is designed to run on regular 120V house voltage. "5 peak hp" certainly sounds impressive..definitely more impressive than a "3 peak hp" unit. Well..neither a 3 or 5 hp motor can run on 120V..both motors (actual 3 & 5 hp) require 220V to run. Where does the 5 peakhp rating come from? It's a marketing gimmick..5 peakhp is a calculated hp rating at the millisecond after the switch is turned on and before any load hits the motor. Totally fictitious claim..in any practical sense. But it sounds impressive.

Before you believe any high efficiency furnace claims, understand how that number is determined relative to what you have. If that proves to be a rabbit hole..then get a new furnace when one is really necessary as opposed to some hoped-for efficiency gain as a upgrade basis. Same goes for new "high efficiency" windows. The efficiency payback on installing new windows tends to be v-e-r-y l-o-n-g.

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Wed Nov 08, 2017 10:50 am

fishboat wrote:
Wed Nov 08, 2017 9:55 am


Before you believe any high efficiency furnace claims, understand how that number is determined relative to what you have. If that proves to be a rabbit hole..then get a new furnace when one is really necessary as opposed to some hoped-for efficiency gain as a upgrade basis. Same goes for new "high efficiency" windows. The efficiency payback on installing new windows tends to be v-e-r-y l-o-n-g.
I agree that the efficiency gains on new furnaces are sometimes not what was warranted. I don't think it is a change in how efficiency is measured.

There is an EIA calculator which, feeding in model numbers, you can do the calculation.

I think the issue is more that the secondary heat exchanger, which moves the efficiency from say high 70s to over 90 per cent, is based on long continuous runs. And most of us probably run the furnace in much shorter "bursts". The HE doesn't get full use then.

It's not a good idea to make the analogy with HE windows. Because it's widely understood that that pays off, if it does at all, at around the lifetime of a PVC U window (i.e. c. 20 years).

Whereas improvements in furnace can have much faster paybacks, one of the best paybacks in fact. Going from a 60% efficiency furnace to a 90% one has a payback, even conservatively, of less than 10 years (and it could be less than 5).

However if you've ever gone from single to double glazing (with heat retentive coat) the improvement both in terms of room comfort and less noise is really noticeable, and it's worth doing from an amenity point of view. As one only does it once, it's worth paying up for heat efficient windows and noise reducing ones.

Valuethinker
Posts: 36742
Joined: Fri May 11, 2007 11:07 am

Re: Furnace Issues

Post by Valuethinker » Wed Nov 08, 2017 10:58 am

fishboat wrote:
Wed Nov 08, 2017 9:55 am


The new one(~$3200) has much higher efficiency..claimed at least..but, honestly, I don't see any difference in gas usage. I live in Wisconsin and burn propane for heat...not cheap compared to NG. Granted, I don't track the gas usage/cost really close, but the before after running costs are anything but dramatic(20%..). Be wary of efficiency claims..how is that efficiency number determined vs how was it determined 28 years ago. If there's a difference, then the new efficiency number is meaningless.
Without tracking consumption v Heating Degree Days you are not going to be able to tell.

The HDD in Wisconsin is so high that a colder or a warmer winter has a big impact on consumption, bigger than a step change to the efficiency of your furnace.

http://www.degreedays.net/

if you have your annual propane consumption you can check it against the HDD. I did find Madison WI on their list-- as an example.

Post Reply