Do I need a new Furnace?

[weatherby460]

Heil, natural gas furnace 16 years old. When it starts, it makes a horrible clunking sound that rattles the duct work.

Gas valve was change earlier in the year because furnace would not start. Inducer motor has been replaced because it was loud last week.
Burners seems clean, has a new furnace filter.

I can hear inducer motor turn on, I think I hear pressure switch click, but then shortly after that is when the clunk happens. Then the furnace runs and sounds fine.

I had a bunch of drywalling done in basement that's when it seem to start.

Thanks for any help, they want to change furnace next.

 

[Jim greengo]

Is it a clunk or a boom?
Have you had the heat exchanger checked?

 

[weatherby460]

Little bit of both.....it happens before the bigger blower motor turns on also. How do I check the heat exchanger?

 

[BillK]

Sounds like it is just having a hard time igniting. Has the igniter been changed ? Can you see it glowing through the sight glass ? My Nordyne furnace is 23 years old and I have had to change the igniter 3 times now. I keep a spare one sitting next to the furnace

 

[BD1]

Before I would change your motor out, I would have recommended replacing entire furnace. At 16 years it's time to change. Sure you can keep doing repairs but a few service calls adds up quick.
Get many estimates. My cost for a 95% upflow single speed is around a $1,000.00
The newer models will most likely be shorter than yours so supply duct will need to be added. It's crazy what they charge for replacement depending where you live.


Sent from my iPhone using Tapatalk

 

[Bert_]

Take the cover off and watch it start up. Should be able to see what is making the thump. Might be time for a new furnace or it might be a $10 DIY fix.

My furnace is about 28 years old and is in good shape, so 16 isn't bad.

 

[Chevy-SS]

Take the cover off and watch it start up. Should be able to see what is making the thump. Might be time for a new furnace or it might be a $10 DIY fix.

My furnace is about 28 years old and is in good shape, so 16 isn't bad.

Yeah, this ^^^^^^^^^^^^^^^^

I own a large two-family house, with two separate forced-air gas furnaces. They are identical and original to the house, both over 35 years old, but still working perfectly because I maintain them myself. I've replaced fan motors and many other parts. In fact, I have a supply of extra parts (fan switch, gas valve, transformer, fan motor, filters) that will allow me to fix pretty much anything when one of the furnaces goes down. And when one goes down, it is usually on a long, holiday weekend where no one is around.

 

[nadogail]

The answer you receive to the question "do I need a new furnace?" may well depend on who you ask.

A furnace salesman will almost always answer yes, an independent tech who does not sell furnaces might say "not necessarily".

Imagine yourself walking into a Barber Shop and asking "Do I need a haircut?"

 

[finn]

I had one that did that. Blower motor had a bad bearing. Got another ten or so yeasts out of it befor the heat exchanger succumbed to old age and cracked.

 

[weatherby460]

I cleaned the ignitor, and so far so good. Always seems to be worse in the mornings for some reason. I am pretty sure when it was doing the banging, it was when the igniter was lit, then the gas started to roll. Not when the big blower started to turn.

 

[mrobins297aaa]

Is it a clunk or a boom?
Have you had the heat exchanger checked?

Jim what do you think the average life of one of 95%+ condensing furnaces are today?
I know from your post you have installed a lot of them.
I've been retired for almost 12 years and before that I always recommended the 80 % furnaces where I could.
what's your thoughts?

anyone else have any thoughts?

 

[Jim greengo]

I prefer 80% furnaces myself in most situations,fewer parts to deal with.
Only time I normally recommend a 90 plus is if the house has a junk chimney and a really tall/steep roof.
I hate doing chimney liners.
Anyway any decent furnace should last 20 years.
If hes hearing the noise when the burners fire up it sounds to me like a roll out,that's why I say to have the heat exchanger checked for cracks.

 

[LS6 Tommy]

Sounds like delayed ignition. Cleaning the ignitor may have helped, but it might just be a temp fix. I'd keep an eye (ear?) on it.

Tommy

 

[James-W]

I tend to be proactive rather than reactive. A furnace isn't going to break down in the middle of Summer, it will break down on the coldest day of Winter. If you can figure out exactly why the furnace has the problem it has, and it can be repaired for a reasonable amount of money, then I would say go ahead and fix it. If you can only guess what the problem is, then I would say get a new furnace.

I have no idea what the typical longevity is for the brand furnace you have, but if it were me in your shoes, I would certainly try to find out. Once you know what the average life expectancy is for the furnace you have, you will have a much better idea whether you should try to repair the furnace, or replace it.

 

[TwoToque]

"Burners seam clean" is not neccessarily good enough for proper flame propogation. You might have to remove them to clean them properly.

 

[Rusty Fords]

I haven't been able to figure how to aply a signature to my post yet
I have a bit of exsperiance in the HVAC trade over 26 years from install to service.

Need a new furnace after 16 years!!! No way or less the heat exchanger is bad and most of the time at that age you can still buy a replacement heat exchanger.
So a 16 year old gas furnace was it a 80% or a 90% plus the 90 plus where available back then (metal flue or a plastic PVC?


Yes cost varies from location so does labor ( Mississippi good techs $20/hr Portland Or $45 plus/hr) Cost to replace well $1000 is not realistic My cost on a 80 or a 90 plus was around $600-$800 plus sheet metal, a good thermostat (not your $50 home depot) case of GOOD quality air filters. Then you got to throw in fuel, insurance, cost of equipment and vehicle repair, taxes SUTA and FICA then you have a technician depending on the application and the required duct work needing to be made 6-8 hours for one guy. Remember business owners aren't in business to loss $ or break even As a previous owner/operator other then some charity jobs for low income families I adopted if I wasn't going to make money I wasn't going to do the job. You can not move a vehicle crossed the parking lot with out costing money. I would put in a gas furnace in a garage ( easy access) for around $1800 and had more of them to do then I could handle.

On efficiency my opinion and multiple others service techs in the trade that are not given a bonus for sales (not sales men). 95%-80%=15% what is your monthly gas heating bill ( please minus other Gas appliances fireplace, stove, water heater, BBQ, drier etc..) when I lived in town I figured my average heating bill was around $900/yr on the high end ( morer like $600) 900x.15 (15%)= $135/ year savings.
$1800/135+13.3 years to regain your cost of investment!!!

As a technician i would rather work one a 80% furnace any day, less components to go wrong. In my opion again 80% with a 2 staged gas valve and a 2 stage thermostat to control it is one of my favorite and is what I had in my last house 8 years old when I sold the place never touched it other then an air filter. You know what they say about cobblers kids... I worked on furnces all day didn't want to work on my own!!!

 

[Jim greengo]

I haven't been able to figure how to aply a signature to my post yet
I have a bit of exsperiance in the HVAC trade over 26 years from install to service.

Need a new furnace after 16 years!!! No way or less the heat exchanger is bad and most of the time at that age you can still buy a replacement heat exchanger.
So a 16 year old gas furnace was it a 80% or a 90% plus the 90 plus where available back then (metal flue or a plastic PVC?


Yes cost varies from location so does labor ( Mississippi good techs $20/hr Portland Or $45 plus/hr) Cost to replace well $1000 is not realistic My cost on a 80 or a 90 plus was around $600-$800 plus sheet metal, a good thermostat (not your $50 home depot) case of GOOD quality air filters. Then you got to throw in fuel, insurance, cost of equipment and vehicle repair, taxes SUTA and FICA then you have a technician depending on the application and the required duct work needing to be made 6-8 hours for one guy. Remember business owners aren't in business to loss $ or break even As a previous owner/operator other then some charity jobs for low income families I adopted if I wasn't going to make money I wasn't going to do the job. You can not move a vehicle crossed the parking lot with out costing money. I would put in a gas furnace in a garage ( easy access) for around $1800 and had more of them to do then I could handle.

On efficiency my opinion and multiple others service techs in the trade that are not given a bonus for sales (not sales men). 95%-80%=15% what is your monthly gas heating bill ( please minus other Gas appliances fireplace, stove, water heater, BBQ, drier etc..) when I lived in town I figured my average heating bill was around $900/yr on the high end ( morer like $600) 900x.15 (15%)= $135/ year savings.
$1800/135+13.3 years to regain your cost of investment!!!

As a technician i would rather work one a 80% furnace any day, less components to go wrong. In my opion again 80% with a 2 staged gas valve and a 2 stage thermostat to control it is one of my favorite and is what I had in my last house 8 years old when I sold the place never touched it other then an air filter. You know what they say about cobblers kids... I worked on furnces all day didn't want to work on my own!!!

What he said.

 

[Bert_]

This is good discussion. Most guys around here won't even give the option of an 80%er unless you specifically ask.

I had kind of wondered weather the added cost and complexity is worth it.

 

[Rusty Fords]

If you are having to replace your furnace already a 90 plus isn't a bad decision specially if there is some kind of rebate but i still perfer a 80%.

When Obama had the recovery act I was putting in 18 seer heat pumps cheaper then I could install a 13 seer. With the federal, manufacture and energy trust rebates I was a hard thing for some people to pass up.

New codes in some locations will not allow a 80% furnace to be installed any more!!

 

[Jim greengo]

I cleaned the ignitor, and so far so good. Always seems to be worse in the mornings for some reason. I am pretty sure when it was doing the banging, it was when the igniter was lit, then the gas started to roll. Not when the big blower started to turn.

What kind of igniter do you have that can be cleaned?
Are you sure you didnt clean the flame sensor?

 

[Showkey]

This is good discussion. Most guys around here won't even give the option of an 80%er unless you specifically ask.

I had kind of wondered weather the added cost and complexity is worth it.

I would not even consider a 80% furnace ..........and jump to 96%.

Venting low cost, Lower maintenance, no roof perforation.
Combustion air, no constant draft or air leak.

Saving + 20% Every month for the life of the furnace. No brainer over the 80%.*

The two stage feature can be debated .......likely no cost saving and added cost......but.........this home came with 90plus two stage variable speed. Having experience the two stage Unit for 6 years. I would Definitely Buy another two stage or multi stage for the comfort of even heating , low noise, low draft. The unit operates in low heat 80-90% of the time. This two stage is currently 22 years old, replace the Variable speed draft inducer with a used unit $80. I have a extra variable speed blower ECM motor ( used) in stock purchased for $90. The whole unit is on borrowed time.

*In another home 15 years back replaced two 80% 125k units that were 20 plus years old........with two 94% single stage 75k units. The NG bill dropped by 45%.

I have 80% shop heater. Replaced that old 20 year unit a few years back for $400. At that time 90% plus unit 50k btu could be purchased for $600. I wish I would have replaced the old unit with 90% unit. The pay back with current low NG prices might take a while. When the new unit was installed class III exhaust pipe upgrade was $150.......so 90% plus PVC vent and make up would have been under $20.

Current 92% 60k is about $1000unit price delivered:
https://www.alpinehomeair.com/viewproduct.cfm?productID=453078415

Current 80% 60k is about $671 unit price delivered:
https://www.alpinehomeair.com/viewproduct.cfm?productID=453078443

 

[jacks2000]

Check the blower wheel for cracks around the hub. If the wheel goes it can also take out the motor.

 

[Bert_]

I would not even consider a 80% furnace ..........and jump to 96%.

Venting low cost, Lower maintenance, no roof perforation.
Combustion air, no constant draft or air leak.

Saving + 20% Every month for the life of the furnace. No brainer over the 80%.*

The two stage feature can be debated .......likely no cost saving and added cost......but.........this home came with 90plus two stage variable speed. Having experience the two stage Unit for 6 years. I would Definitely Buy another two stage or multi stage for the comfort of even heating , low noise, low draft. The unit operates in low heat 80-90% of the time. This two stage is currently 22 years old, replace the Variable speed draft inducer with a used unit $80. I have a extra variable speed blower ECM motor ( used) in stock purchased for $90. The whole unit is on borrowed time.

*In another home 15 years back replaced two 80% 125k units that were 20 plus years old........with two 94% single stage 75k units. The NG bill dropped by 45%.

I have 80% shop heater. Replaced that old 20 year unit a few years back for $400. At that time 90% plus unit 50k btu could be purchased for $600. I wish I would have replaced the old unit with 90% unit. The pay back with current low NG prices might take a while. When the new unit was installed class III exhaust pipe upgrade was $150.......so 90% plus PVC vent and make up would have been under $20.

Current 92% 60k is about $1000unit price delivered:
https://www.alpinehomeair.com/viewproduct.cfm?productID=453078415

Current 80% 60k is about $671 unit price delivered:
https://www.alpinehomeair.com/viewproduct.cfm?productID=453078443

More thoughts and questions,

I would still need to maintain a chimney for my gas water heater. Guessing I'm not the only one with that problem.

What is the real difference in efficiency if the 80%er doesn't pull combustion air from the living space? Mine is in the basement so it pulls semi conditioned air, 55-60* air. Surely that factors into the efficiency, but how much?

I have also seen some low buck installs where the installer sold a high efficiency furnace but did not run the air intake outside. How much does this lower the efficiency? Pretty sure it is allowed under the same circumstances as the 80%er.

 

[weatherby460]

So what happens is, when the gas comes on and ignites, the gas flame briefly goes out, and then the gas flame comes back on again, that's when the noise happens. Still no idea what the issue is.

 

[Showkey]

More thoughts and questions,

I would still need to maintain a chimney for my gas water heater. Guessing I'm not the only one with that problem.

What is the real difference in efficiency if the 80%er doesn't pull combustion air from the living space? Mine is in the basement so it pulls semi conditioned air, 55-60* air. Surely that factors into the efficiency, but how much?

I have also seen some low buck installs where the installer sold a high efficiency furnace but did not run the air intake outside. How much does this lower the efficiency? Pretty sure it is allowed under the same circumstances as the 80%er.

Power vent water heater.......vented with PVC through side wall.

Experts in prior post ........confirmed the efficiency Rating of the 90+ furnace is not effected by out side air make up air. The outside make up is important ( critical) in the overall seal or air exchange rate of the home. 80% vented constantly open draw is like having a window open 24/7/365.

 

[ambenz]

Your mixing fuel with air seeping thru the heat exchanger....

 

[Showkey]

So what happens is, when the gas comes on and ignites, the gas flame briefly goes out, and then the gas flame comes back on again, that's when the noise happens. Still no idea what the issue is.

Is this a mechanical sound or booming ( explosion ) Vibrating the duct and furnace ?

Sounds like a rough start ? Watch the gas flame travel across the burners. It should light witha even flame travel across all the burners.

RUST and Corrosion on the burners can cause and uneven flame travel and gas build up where it can boom. There are flame travel slits in the burners that clog or rust up.

Uneven or rough start often shuts the gas valve down as the flame sensor is not satisfied.

Excessive gas pressure can cause rough start or booming.

Maybe video the flame and noise to give more info for others to troubleshoot.

 

[weatherby460]

I do have a good video of this happening, but not sure how to post it.

 

[brewchief]

Has the furnace been properly cleaned? I'm talking about removing and cleaning the burners, preferably by washing them with water, if they are rusty and in bad shape they may need replacement. This should be followed by a proper combustion test, you simply cannot do a proper tuneup on a fuel fired appliance without using a combustion analyzer. Heat exchanger needs to be visually checked for cracks, holes, etc.
A failed heat exchanger on a 16 year old furnace is not uncommon, however I would bet that a proper cleaning fixes your problem, the fact that it started after drywall work is a good clue.

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[Jim greengo]

Power vent water heater.......vented with PVC through side wall.

Experts in prior post ........confirmed the efficiency Rating of the 90+ furnace is not effected by out side air make up air. The outside make up is important ( critical) in the overall seal or air exchange rate of the home. 80% vented constantly open draw is like having a window open 24/7/365.

Yes drawing in air that's already been heated to use as combustion air affects the efficiency rating of a furnace.
Theres a reason why it's designed that way,and yes I've been in the business a long time.

 

[weatherby460]

The burners looked good to me, but I will take another look tomorrow to make sure.

 

[Showkey]

Yes drawing in air that's already been heated to use as combustion air affects the efficiency rating of a furnace.
Theres a reason why it's designed that way,and yes I've been in the business a long time.

Agree......Outside is preferred. Should it be done absolutely. Makes the building tighter and easier heat.

Prior discussion. Poster is Also a professional ? so this is his post ? Somewhat a moot point as outside Air is huge benefit to the building efficiency.
See post #5 in:

https://www.garagejournal.com/forum/showthread.php?t=453060

“The furnace manufacturer does not say that the furnace will be more efficient by sucking in outside air...because it won't be. Furnaces are rated on the percentage of available heat from the fuel source that makes it into the air stream being blown into the ducts. They don't have to deduct for the loss that will occur when you **** (heated) combustion air out of the house and then have to reheat cold air getting sucked in around windows and doors or through other gaps that will now have to be heated by the furnace.“

 

[HoosierBuddy]

Jim what do you think the average life of one of 95%+ condensing furnaces are today?
I know from your post you have installed a lot of them.
I've been retired for almost 12 years and before that I always recommended the 80 % furnaces where I could.
what's your thoughts?

anyone else have any thoughts?

I personally would never recommend any 80% furnace, and I sell gas for a living.

The newer fully condensing furnaces with 2 stages or modulating are not only cheaper to operate, but also produce a more comfortable environment.

Besides saving the bill payer money, higher efficiency gas furnaces also conserve a non-renewable energy source and lower green house gas emissions.

Regarding guys that are riding really old furnaces, yes they can last a really long time. When I bought my house it's furnace was between 35 and 40 years old, was in great shape, and its replacement was one of the things I accomplished in renovating the house the first few years we lived there. It was plate rated at 80%, but my guess is it was more like 60% efficient. I mean, when you see a plate that says 200,000 BTU Input, 160,000 BTU Output....how much testing do you REALLY THINK they made them do to come out with those numbers? 80.00000000000000000000000% efficient. Numbers like that got written by the Marketing Manager back in the day, not any sort of test engineer.

The house is currently rocking a 2 stage 70,000 / 100,000 BTU input furnace (I think it's like 93%) and it's way more comfortable than it was with "the beast" we got when we bought the house.

Phil

 

[Jim greengo]

I personally would never recommend any 80% furnace, and I sell gas for a living.

The newer fully condensing furnaces with 2 stages or modulating are not only cheaper to operate, but also produce a more comfortable environment.

Besides saving the bill payer money, higher efficiency gas furnaces also conserve a non-renewable energy source and lower green house gas emissions.

Regarding guys that are riding really old furnaces, yes they can last a really long time. When I bought my house it's furnace was between 35 and 40 years old, was in great shape, and its replacement was one of the things I accomplished in renovating the house the first few years we lived there. It was plate rated at 80%, but my guess is it was more like 60% efficient. I mean, when you see a plate that says 200,000 BTU Input, 160,000 BTU Output....how much testing do you REALLY THINK they made them do to come out with those numbers? 80.00000000000000000000000% efficient. Numbers like that got written by the Marketing Manager back in the day, not any sort of test engineer.

The house is currently rocking a 2 stage 70,000 / 100,000 BTU input furnace (I think it's like 93%) and it's way more comfortable than it was with "the beast" we got when we bought the house.

Phil

When your new furnace is 40 years old how efficient do you think it's going to be?
Sometimes it's just not practical to install a 90 plus furnace,

 

[Jim greengo]

Agree......Outside is preferred. Should it be done absolutely. Makes the building tighter and easier heat.

Prior discussion. Poster is Also a professional ? so this is his post ? Somewhat a moot point as outside Air is huge benefit to the building efficiency.
See post #5 in:

https://www.garagejournal.com/forum/showthread.php?t=453060

“The furnace manufacturer does not say that the furnace will be more efficient by sucking in outside air...because it won't be. Furnaces are rated on the percentage of available heat from the fuel source that makes it into the air stream being blown into the ducts. They don't have to deduct for the loss that will occur when you **** (heated) combustion air out of the house and then have to reheat cold air getting sucked in around windows and doors or through other gaps that will now have to be heated by the furnace.“

By all means call up a furnace manufacturer and ask them .

 

[Jim greengo]

Does a car engine make more hp sucking hot air from a sealed up engine compartment,or from a functioning coal induction set up bringing in colder air from outside?

 

[Showkey]

Does a car engine make more hp sucking hot air from a sealed up engine compartment,or from a functioning coal induction set up bringing in colder air from outside?

You best stick with HVAC........cuz comparing a car engine to furnaces, your way out on limb. One is internal combustion, compression with air density, temp adjusted mixture control and the other is external combustion.

 

[Jim greengo]

News flash chief,I've been putting really nasty small block and big block chevys together for a lot of years.
Cold air is cold air its denser and burns a whole hell of a lot better than hot air.
It doesnt matter if it's in a furnace in your basement or in the combustion chamber of an LS6 or 7 454.
Mean while go out and service/install hvac equipment for 30 years ,then come back and talk to me about furnaces and air conditioning.

 

[FJ 432]

News flash chief,I've been putting really nasty small block and big block chevys together for a lot of years.
Cold air is cold air its denser and burns a whole hell of a lot better than hot air.
It doesnt matter if it's in a furnace in your basement or in the combustion chamber of an LS6 or 7 454.
Mean while go out and service/install hvac equipment for 30 years ,then come back and talk to me about furnaces and air conditioning.

MY BIL and his company (30+ years) has your same opinion.

 

[Jim greengo]

MY BIL and his company (30+ years) has your same opinion.

Thank you.