The Carrier furnace in my dad's house is 33 years old.
Is this thing on borrowed time?
Is this thing on borrowed time?
How long can a furnace heat exchanger last?
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Kestas
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It depends.... the amount of thermal cycling, how well it's made, the materials used in manufacture.
My furnace has 35 years on it. It's been repaired a few times, but the heat exchanger still looks good.
My furnace has 35 years on it. It's been repaired a few times, but the heat exchanger still looks good.
I think you keep checking it. If it's fine it's fine.
I'd be afraid of replacing it and having the new one crack in a few years.
I'd be afraid of replacing it and having the new one crack in a few years.
At 33 years it has done a stellar job. My Trane natural gas furnace lasted 25 years before the heat exchanger started developing tiny pin holes. Scary to see flames through those tiny holes in the fire box! I immediately replaced it with another Trane.
The Lennox furnace my parents had installed in our then-new house in 1957 was still going strong when my mother sold the house in 1991, including the original heat exchanger and fan motor. An evaporator coil for central air conditioning was added in 1971.
1) As long as the house has a working carbon-monoxide detector that is less than 10 years old then they should be safe. I have two that are older than 10 years but still probably would work, and one that is new that definitely would work.
2) Also I keep enough electric heaters to heat the house if the gas or furnace ever went out.
Our cheap furnace was 20 something years old when the heat exchanger was leaking a small amount of CO into the air and the CO detector we had has a digital display of the amount of CO. It was not enough to set off the audio alarm, but it was not zero. My cousin who has a heating and refrigeration business at first said it was probably just some back-draft leakage from the gas water heater, so I replaced that with a gas water heater that has coaxial pipe and brings in the outside air and pipes the exhaust inside a pipe that is inside the intake pipe, so there is no way to get a back-draft leakage into the house because it does not have any parts of the intake or exhaust open to the house air. That water-heater with coaxial pipe cost me $1600 and I installed it myself. The CO detector still would not register zero, so my cousin inspected our forced air furnace and found that some of the big rivets that hold the two halves of the heat exchanger together had fallen out because of all the heat cycles it saw and it was leaking CO so he shut off the gas to it, and red tagged it, and it was winter. Fortunately I had bought enough electric heaters to keep the house at the normal temperature, and my brother an I had rewired the whole house so all the wiring was up to handling the load. The heat exchanger was still under warranty, but even with the family discount it was expensive to get them to do the labor to replace it.
BTW, those electric heaters have also been handy to have when the control board on our furnace fried one winter, when my sisters furnace died, and when a neighbors furnace died. I have 13 electric heaters and use them on the low 1,000 watt setting. When my neighbors furnace died he asked me if I had any electric heaters he could borrow, and I said boy did you ask the right person.
2) Also I keep enough electric heaters to heat the house if the gas or furnace ever went out.
Our cheap furnace was 20 something years old when the heat exchanger was leaking a small amount of CO into the air and the CO detector we had has a digital display of the amount of CO. It was not enough to set off the audio alarm, but it was not zero. My cousin who has a heating and refrigeration business at first said it was probably just some back-draft leakage from the gas water heater, so I replaced that with a gas water heater that has coaxial pipe and brings in the outside air and pipes the exhaust inside a pipe that is inside the intake pipe, so there is no way to get a back-draft leakage into the house because it does not have any parts of the intake or exhaust open to the house air. That water-heater with coaxial pipe cost me $1600 and I installed it myself. The CO detector still would not register zero, so my cousin inspected our forced air furnace and found that some of the big rivets that hold the two halves of the heat exchanger together had fallen out because of all the heat cycles it saw and it was leaking CO so he shut off the gas to it, and red tagged it, and it was winter. Fortunately I had bought enough electric heaters to keep the house at the normal temperature, and my brother an I had rewired the whole house so all the wiring was up to handling the load. The heat exchanger was still under warranty, but even with the family discount it was expensive to get them to do the labor to replace it.
BTW, those electric heaters have also been handy to have when the control board on our furnace fried one winter, when my sisters furnace died, and when a neighbors furnace died. I have 13 electric heaters and use them on the low 1,000 watt setting. When my neighbors furnace died he asked me if I had any electric heaters he could borrow, and I said boy did you ask the right person.
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Straight from a friend in the business... new ones don't last as long as old ones. They are made of thinner, lighter material for better heat transfer and efficiency.
If you have a 20 year old exchanger, it may outlast your neighbor's installed yesterday.
If you have a 20 year old exchanger, it may outlast your neighbor's installed yesterday.
My gas furnace was new in dec 1995. In reading this thread, i did not realize that CO detectors need to be replaced every 10 years. I have a Nighthawk digital, thats 25 years old. I ordered a new one tonight.
Thanks for the thread!
Thanks for the thread!
As for backup electric heaters. I looked for reduced prices at Wallmart in the spring. Some Walmarts mark them down and some do not. The cheap plastic housing ones I bought have a low setting of 1,000 Watts and a high setting of 1,500 Watts, but when you use the high setting you can smell the plastic, so I never use that setting. 1,000 Watts of electric resistive heating produces 3412 BTUs. Figure that on a very cold day a properly sized furnace may run something like 60 to 80 percent of the time. So if the house has a 50,000 BTU furnace 0.8 X 50,000BTUs = 40,000 BTUs so 40,000 BTUs of electric heating should be able to keep that house at normal temperature on a very cold day. 40,000 / 3412 = 11.7 so 12 or more electric heaters that can run at 1,000 Watts each should produce enough heat to keep that house warm on a very cold day.
Of course if the house has a furnace that is larger than 50,000 BTU then you will have to do the math for that size furnace.
It is better to have too many, then to not have enough. Even when I did use them with only the 1,000 Watt setting on each, they did cycle off often ( but is was not the coldest day of winter ), so we could of got by with less of them. But again it is better to have too many then not enough.
Of course if the house has a furnace that is larger than 50,000 BTU then you will have to do the math for that size furnace.
It is better to have too many, then to not have enough. Even when I did use them with only the 1,000 Watt setting on each, they did cycle off often ( but is was not the coldest day of winter ), so we could of got by with less of them. But again it is better to have too many then not enough.
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Also burning candles, especially scented candles will leave a very small film deposit on sensors and ruin them.
Our Carrier is entering its 25th heating season. Its last inspection showed the exchanger was still looking good. We've heard similar things that the new stuff has had more of the life engineered out of them...
I'll echo the comment on having your CO detectors replaced within their service life - typically 7-10 years. We make sure we have at least one that reads the CO level and displays it - as was pointed out in another post, it can take a lot to set one of these off, while in the meantime you have a low level leak...
I'll echo the comment on having your CO detectors replaced within their service life - typically 7-10 years. We make sure we have at least one that reads the CO level and displays it - as was pointed out in another post, it can take a lot to set one of these off, while in the meantime you have a low level leak...
If you ask a home inspector, they will say around 15-20 years for a furnace. But you could get lucky as other people on here and have it last longer, I've seen them last 30-40 years. You should check your state's energy programs. Usually there's some rebate for high efficiency systems. Sometimes they expire in the winter and start up in the spring so you might want to consider replacing it. Most older systems are only 80% efficient and the older they are, the more degradation you get in the system. The newer ones can go up to 95% or more, but those are usually direct vent systems.
Has it been plugged in and powered on? They only lasted 7 years because they used an electrochemical sensor that was only good for 7 years. It should beep all the time when it reaches the 7 year lifespan. I think it uses a simple counter to count the time it's been powered on to reach 7 years. I've had a few that lasted 10+ years because the tenant took the battery out. The newer ones use sensors that can last 10 years, but it's still the same type of sensor.
I wonder if it's too old to have a counter. Yes plugged in.
Should have a date on it in the back. I guess the really old ones didn't have any alarm when the sensor was too old.
https://en.wikipedia.org/wiki/Carbon_monoxide_detector
The old ones did not alarm like the newer ones do. I replaced a 14 year old on at a secondary property a few years back...
We have 2 Carrier NG heat units, both are starting their 30th Winter season. The new carrier stuff is junk I hear though.
If it hasn't cracked yet, rust is what is going to put an end to your heat exchanger. Problem is 40-50 percent of his heat is going up the chimney.
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