The heat is off (sort of)

[redduck]

I don't know anything about this stuff, but maybe some of you do:
Our furnace (big machine-like thing that heats up the house) has kind of stopped w*rking. Anyhow, it will get the temperature up to 64 but that's it. No more 68 degrees for us. It will go on with a big whooshing sound, but just plain stops at 64. Any idea what this all might mean? (other than it means $6,000). Hopefully, we will have a heating guy come in tomorrow (or, the next day or so), but I'd kind of like to know what we are in for.

Guess I should mention that the furnace (big machine-like thing that heats up the house) is 42 years old. Did it FIRE without telling us? How could it retire at 42?

 

[Alan]

I don't know anything about this stuff, but maybe some of you do:
Our furnace (big machine-like thing that heats up the house) has kind of stopped w*rking. Anyhow, it will get the temperature up to 64 but that's it. No more 68 degrees for us. It will go on with a big whooshing sound, but just plain stops at 64. Any idea what this all might mean? (other than it means $6,000). Hopefully, we will have a heating guy come in tomorrow (or, the next day or so), but I'd kind of like to know what we are in for.

Guess I should mention that the furnace (big machine-like thing that heats up the house) is 42 years old. Did it FIRE without telling us? How could it retire at 42?

42 years = 126 furnace years

 

[Dimsumkid]

Anyhow, it will get the temperature up to 64 but that's it. No more 68 degrees for us. It will go on with a big whooshing sound, but just plain stops at 64. Any idea what this all might mean? (other than it means $6,000). Hopefully, we will have a heating guy come in tomorrow (or, the next day or so), but I'd kind of like to know what we are in for.

How could it retire at 42?

Seems like the heat still works, something is stopping the heater from going above 64 consistently? It may be a thermostat issue, one (or more) of the safety sensors is getting tripped or the limit switches are getting triggered. The sensors or limit switches are there to prevent overheating situations. Hard to tell what is causing your problem w/o seeing it. I had a sensor that kept tripping after a HVAC guy came to do an inspection....he left the heat deflector slightly ajar and that tripped it each time the heat turned on.

By the way, 42 yrs is about 22 - 25 yrs past it's normal replacement time! Hopefully, you've been getting it checked annually!

 

[TromboneAl]

If it always stops at 64 exactly, I'd guess that you just need a new thermostat.

 

[Bestwifeever]

Some people here wouldn't even know if their furnaces go above 64 because they don't set the heat that high .

(I think it's the thermostat too.)

 

[meierlde]

A couple thoughts first is it gas or oil? With a woshing sound it does sound like an oil furnace. If gas is available now if replacing think about going gas. Note that efficiencies in furnaces that old are likely in the 40-50% range where as today 80% is a minimum. I assume its an old thermostat, so take the cover off and push the thermostat up and see if the mercury flash tips. You can probably eliminate the thermostat by pushing it up to 76 and seeing where the temp stops rising.
If you take the cover off the thermostat you may see a mercury bulb that tips as the temp is adjusted. Set the stat up and see if the bulb goes to the off position at 64 (I doubt it would). That would imply that some of the safety equipment on the furnace is no longer working right.

 

[redduck]

Is it significant that the furnace fan won't turn off and now we have a wind-chill factor to contend with? (The thermostat is turned to "automatic"; the only other choice is "on").

 

[redduck]

Some people here wouldn't even know if their furnaces go above 64 because they don't set the heat that high .

(I think it's the thermostat too.)

OK, Bestwifeever...This is a man thing (minus Redduck). Don't you have a cake to bake or something? Actually, "man thing" doesn't sound quite right, sorry.

 

[meierlde]

Is it significant that the furnace fan won't turn off and now we have a wind-chill factor to contend with? (The thermostat is turned to "automatic"; the only other choice is "on").

In the past did the furnace come on and then the fan, or the fan first? If its the latter then it sounds like the temp sensor of the heat core in the furnace that kicks the blower on may have failed. What typically happens is that the burner comes on and heats the heat core (bonnet) up to about 165 and then the blower comes on. So you may have a set of failures in the control systems of the furnace, in terms of several temp sensors at one time.

 

[redduck]

A couple thoughts first is it gas or oil? With a woshing sound it does sound like an oil furnace. If gas is available now if replacing think about going gas. Note that efficiencies in furnaces that old are likely in the 40-50% range where as today 80% is a minimum. I assume its an old thermostat, so take the cover off and push the thermostat up and see if the mercury flash tips. You can probably eliminate the thermostat by pushing it up to 76 and seeing where the temp stops rising.

It's gas. And, the thermostat is about 5 years old. I'm assuming that the fan running is not dangerous, but if redduck doesn't show up on the board tomorrow, well...maybe he underestimated the running fan. Hope the heating guy shows up.

 

[redduck]

In the past did the furnace come on and then the fan, or the fan first? If its the latter then it sounds like the temp sensor of the heat core in the furnace that kicks the blower on may have failed. What typically happens is that the burner comes on and heats the heat core (bonnet) up to about 165 and then the blower comes on. So you may have a set of failures in the control systems of the furnace, in terms of several temp sensors at one time.

I'm pretty sure the fan would come on first, then the furnace.
So, assuming you are correct about the set of failures in the control systems, does that mean a new furnace is the reasonable solution?
And, thanks for the information.

 

[travelover]

I had a 40 year old furnace and when I had an energy efficiency audit done, the advice was let it run until it fails. I let it run about 4 more years and got tired of waiting for it to die, so I replaced it for about $3500. Estimates for the same furnace varied widely.

My old gas furnace did the whoose thing, too. Unnerving, but never seemed to cause any issues.

 

[Walt34]

Being 42 years old you definitely got your nickel's worth out of that furnace. Even if you don't need a new one now be prepared to replace it any day now.

Since it heats at all I'd suspect one of the control circuits, safety circuits that prevent heat exchanger overheating, or the thermostat. None of those are terribly expensive.

Ask the service guy to take a good hard look at the heat exchanger. That's the part that is the "heart" of a furnace and separates the fire (gas or oil) from the air being heated. If there is a hole in it you can get carbon monoxide in the house air and you go to bed with a bit of a headache and never wake up.

Kinda puts a damper on retirement plans.

 

[Midpack]

I'd guess thermostat too. But you got way more than twice the life out of your furnace than we did. If you do have to replace, modern furnaces are far more efficient, so there is some upside. Good luck!

 

[My Dream]

Based on what I've read it seems to be related to the thermostat.


Here in Canada, they only produce high efficiency furnaces now which means at least 90% efficient. Also if you're on natural gas and a tech comes in to diagnose and finds a problem with your furnace such as a crack in your heat exchanger which is safety related, they can red tag your furnace and shut off the gas to the furnace until the safety issue is resolved.
I found that we used to have a 100,000 but mid efficiency furnace which after 26 years it went from 80% efficiency to around 69%. When we purchased our 66,000 btu 95% to heat the same size house, we saved around 25 % per year in natural gas and found it much more comfortable since it was even distribution heat.
Let us know how you make out.

 

[frank]

I had a furnace check my furnace when it was making the whooshing noise and it was the ignitor, which was cheap. but then the part with the 64 degrees and the blower running all the time seems like the thermostat problem. most is fairly cheap to fix. If your furnace is 42 years old then I would definitely check into the 95% efficient furnaces available today. with the energy rebates available and the savings on gas I would think it would be a good investment.

 

[ronin]

This is a trick question, because we all know doesn't get below 64 degrees in L.A.!

 

[REWahoo]

This is a trick question, because we all know doesn't get below 64 degrees in L.A.!

+1

When I saw the post my first thought was "Why would you need a furnace in LA?"

 

[redduck]

This is a trick question, because we all know doesn't get below 64 degrees in L.A.!

Sure, just pile it on, while I'm sitting here in my Land's End maroon bathrobe, gloves (with the finger-tips cut out) and a pull-down-over- the-ears cap that says "No Fear" on it.

Anyhow, the heating guy is coming to the house this morning, so I'll let all you folks (except for REWahoo, who tricked me into buying totally worthless, yet painful and humiliating deferred gratification clamps) know how this all ends.

 

[Sue J]

When we moved into our house in 1983 the furnace was the original one from 1955. Anytime we had maintenance done on it they told us that it's old but it's good so keep it until it dies. It died last January at age 56 when it need a part from the previous century.

We bought a nice 95% efficient one and it's been great. It's hard to tell how much savings is attributed to the new furnace because we also had just installed all new energy efficient windows, too. Overall, at least 30% reduction in natural gas usage with both improvements. This is in Ohio, which has a real winter heating season for at least 5 months.

 

[Bestwifeever]

OK, Bestwifeever...This is a man thing (minus Redduck). Don't you have a cake to bake or something? Actually, "man thing" doesn't sound quite right, sorry.

When I bake a cake I like to leave the oven door open afterwards so any extra heat can warm up the house. Try that

 

[Dimsumkid]

What kind of thermostat is this? Is this a manual dial round thermostat or a newer digital one? If it's a manual round (I think this was a Honeywell), you should check it with a level, it may have loosen and needs to be releveled to fix it. If you're somewhat handy, all the thermostat does is tell the heat to turn on/off. Check to see that's it's low voltage, under 24v, if so, there's two wires for heat that you can just twist together that will basically bypass the thermostat and would eliminate the thermostat as the issue. If it has batteries, check and replace these as needed too.

 

[travelover]

When I bake a cake I like to leave the oven door open afterwards so any extra heat can warm up the house. Try that

If you left the door closed, where would the heat go?

 

[Bestwifeever]

If you left the door closed, where would the heat go?

Into the cake, of course.

 

[Avalon]

I'd like to second what Walt was saying about the heat exchanger on a unit this old. Have it examined closely for cracks. I've actually seen one so bad that the burner flames were blown sideways when the fan kicked on. Quite a fire hazard.

Best of luck