Failed LP Heat Exchanger

patrick6x

Hi all,

I just bought this house a few months ago towards the last hot month of summer. Through the few days it was on the AC ran great & no problems there. 

Fast forward now to the cold of winter. I have a Carrier 92 manufactured in 2004. I am completely remodeling the house so there is dust everywhere. The furnace has been running for a few months perfectly fine with no problems. 

The 500 lb propane tank that came with the house was getting low near 20% and I had a new company install a new tank when the old tank reached about 15%. The installer of the new propane tank changed the regulator on the house as it was very old. 

(I am not living at the house currently, it is in remodel stage)
 

Approximately 2 weeks after new propane tank & regulator installation I started to smell a little bit different scent outside from the exhaust. It was very minor so I thought nothing of it. 

About a week after that in the dead of winter I arrive at the house & the thermostat is off & the furnace is blowing room temperature air. I go down to check & the burners are not lit. I replaced the air filter which was very dirty & cleaned out any other dust that was down near the fan. 

I hit the reset button and runs fine & cycles through the night. I come back the nest day and it is up & running great. After working for a few hours at the house I notice the same thing happened. Thermostat is off & it is just blowing air. I go to observe & the burners are off & code reading on the control panel. 

I went through some troubleshooting with HVAC guy on the phone & he asked if the burner cover plate was warm & it was, I had to take it off with gloves. After observing the burner tubes I noticed minor soot on the outside of the tubes. He mentioned the combination of the hot cover plate & spot on the tubes may be the result of a bad heat exchanger. 

I am going to get a few professional opinions of people to look at it prior to making any final decisions. 

Can a filthy air filter cause the heat exchanger to fail? Can a new propane tank & regulator cause the furnace to run too rich or low? I know there are videos on cleaning a heat exchanger. Can that be done? 

Any input or suggestions would be greatly appreciated. Thank you in advance!

clammy

At 18 years old that’s about right for failure , hot air heat exchanger are not like a cast iron boiler a different beast . As for running low on propane has zero to do w heat exchanger failure , heat exchanger crack and fail it’s a fact of life some a shorter life span then others depending upon proper supply and return duct work , cleanliness of return grill ducts and filter and being the ac ,how clean is that all these minor issue can and will cause low air causing more then designed expansion and contraction of the heat exchanger and if the units heating side is over side then rampant short cycling does not help heat exchanger life span which I believe I’d usually warranted for about 20 years so your right in line w replace,met of the furnace . I would suggest get a decent co dectector w a digital read out so even if it does not alarm it’s gives you a read out of co level s a wise idea for any hot air furnace in my eyes . Peace and good luck clammy

pecmsg

patrick6x said:

Hi all,

I just bought this house a few months ago towards the last hot month of summer. Through the few days it was on the AC ran great & no problems there. 

Fast forward now to the cold of winter. I have a Carrier 92 manufactured in 2004. I am completely remodeling the house so there is dust everywhere. The furnace has been running for a few months perfectly fine with no problems. 

The 500 lb propane tank that came with the house was getting low near 20% and I had a new company install a new tank when the old tank reached about 15%. The installer of the new propane tank changed the regulator on the house as it was very old. 

(I am not living at the house currently, it is in remodel stage)
 

Approximately 2 weeks after new propane tank & regulator installation I started to smell a little bit different scent outside from the exhaust. It was very minor so I thought nothing of it. 

About a week after that in the dead of winter I arrive at the house & the thermostat is off & the furnace is blowing room temperature air. I go down to check & the burners are not lit. I replaced the air filter which was very dirty & cleaned out any other dust that was down near the fan. 

I hit the reset button and runs fine & cycles through the night. I come back the nest day and it is up & running great. After working for a few hours at the house I notice the same thing happened. Thermostat is off & it is just blowing air. I go to observe & the burners are off & code reading on the control panel. 

I went through some troubleshooting with HVAC guy on the phone & he asked if the burner cover plate was warm & it was, I had to take it off with gloves. After observing the burner tubes I noticed minor soot on the outside of the tubes. He mentioned the combination of the hot cover plate & spot on the tubes may be the result of a bad heat exchanger. 

I am going to get a few professional opinions of people to look at it prior to making any final decisions. 

Can a filthy air filter cause the heat exchanger to fail? Can a new propane tank & regulator cause the furnace to run too rich or low? I know there are videos on cleaning a heat exchanger. Can that be done? 

Any input or suggestions would be greatly appreciated. Thank you in advance!

That furnace was never designed for use during construction. The plugged filter and age are the likely reason for the failure.

wmgeorge

Ditto seen many furnaces and AC coils ruined by construction dust. The drywall sanding dust is the worse. Carrier may not warranty because of user neglect. You can pay an authorized Carrier dealer for a service call to submit a claim, but hold off on a new one until you get your job done.

JUGHNE

Also household furnaces are designed and intended to heat a heated house that is consistly 60-70 degrees or so.

If room temp drops low perhaps overnight and then furnace comes on it may have too much condensation in the heat exchangers....even though it may be a condensing furnace. IMO

We have always used old electric furnaces for temp const. heater.
They were take outs from change outs.
10-15 KW unit lying on sawhorses, temp power cable from panel or range outlet.