The furnace is part of an HVAC or central heating system used to generate heat. Typically this is done with gas, a heat pump, or an electric element. For hot water and radiator based heating, use the boiler tag.

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532 views

Where do I connect the C wire in my furnace?

I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and ...
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1answer
58 views

my furnace fan stays on even when at temperature

I recently installed a 2nd generation NEST thermostat. I'm not home very often, but I was paying particularly close attention to the furnace after installing this thermostat and I noticed that the ...
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2answers
237 views

What could be causing my furnace burners to fire up, then shut off due to partially open door?

I have a 10 year old Carrier gas furnace that keeps shutting off every 24-48 hrs. First I thought it might be the flare sensor but then I checked the bottom door and it wasn't completely closed. I ...
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1answer
23 views

Goodman GM100 Failure to recycle

Our Goodman Furnace Model GM100 Serial# 9412063230 will start up and run but will not recycle after initially satisfying the thermostat. If you wiggle the gray,(ground), wire on the gas valve, it ...
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1answer
36 views

Where is my Common Wire? [duplicate]

I purchased a wifi thermostat and cannot located the common wire. My unit is old and is a Coleman 70 with no terminals inside labeling the wires. As you can see in the second image, there is a ...
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11 views

Can I add another heat run to my furnace?

I'm looking to add a bedroom to the basement and would like to add a heat run to the new room (return air will occur through an opening between the ceiling joists). This seems easy enough, but I ...
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2answers
34 views

Lennox G40UH takes a long time for the heat to come on

The digital thermostat lights up with "HEAT ON" but it takes the furnace up to an hour to kick start. Once it does, it puts out heat. We set it to 69 here in Michigan with the outside temp at Zero. ...
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1answer
227 views

How can I replace an old dial thermostat on an oil furnace with Hydrostat 3250 Plus?

I recently bought a home with an oil fired Biasi furnace that has a Hydrostat 3250-Plus attached. It uses an old analog round dial thermostat, and I'd like to replace it with a new digital (wifi) ...
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2answers
17k views

Gas furnace kicks on then off frequently

A few times in the past week I will wake up to my furnace turning on, hearing a click when it tries to ignite, then turn off. This will happen for a couple minutes before the furnace quits trying. ...
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1answer
120 views

Is there any way to stop the air leak through my furnace without compromising its operation?

My house has an 80% efficiency gas furnace in an interior mechanical closet with the return air path below the furnace and through a grille under the closet. However, since the furnace is not a sealed ...
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1answer
91 views

Why would only 1/3 of my registers be blowing warm air?

I have a Coleman gas furnace in a wall space in my house which somehow shares the blower on my a/c unit on the roof because it turns on when furnace is called to start, though it does bump up after a ...
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1answer
380 views

Why is my new high efficiency furnace blowing cold air sometimes?

Why does my new furnace high efficient Payne furnace blow cold air,not constantly but at least 3 different times in a day, my thermastat is set on auto but when the weather is cold outside it will ...
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2answers
324 views

Could wind be causing my high efficiency furnace exhaust to back up into the house?

I am Toronto based, and just installed a new high efficiency furnace (York YP9C 080 model) in November. Later on I smell odor in my house when the heat started. It is more apparent when it is a gusty ...
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1answer
14 views

Where should I connect the C wire in my furnace, trying to upgrade my thremostat?

I am upgrading my thermostat to a Honeywell Wifi one, and would like to add a common wire. My current furnace controller has 3 blue wires at the 24 v end of the transformer. Which of these (blue) ...
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3answers
89 views

Closing off heating ducts

We have a natural gas furnace that currently heats our entire 2400 square foot home. We plan on putting in a rental suite in the basement which will require closing up all the duct work into the suite ...
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1answer
280 views

Can I relocate my furnace exhaust?

When my new furnace was installed, the vent was put outside the house next to landscaping bushes. It has killed one of my bushes. It used to be vented up to my roof and out. Can I move this outside ...
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1answer
376 views

What could be causing vibration in my furnace?

I have a vibraton in furnace only when flame is lit. Blower motor seems fine. Is this vibration normal? Recently replaced inducer motor. Heat exchanger has been replaced once. Does not appear to be ...
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2answers
74 views

What could cause the blower in my furnace to come on?

Ok my blower just turned on, my propane furnace and it's not in operation due it being summer. My thermostat is set at 65 and the room temp is 78. The heater never actually fired it was only the ...
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1answer
764 views

Why is my furnace blower running at low speed?

My Payne gas furnace (PG8UAA 42091) automatically shuts down after it lights and burns for two minutes. It then gives a 33 fault code. I've done some research and some testing and have narrowed the ...
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1answer
489 views

Why is my furnace blowing hot air outside?

So I have been having trouble heating my home. I noticed today that there is a vent blowing hot air outside. It is not the return, chimney or venting. Any ideas other that the builder thought we ...
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1answer
44 views

New Furnace won't turn on after trying to install thermostat

I had a furnace installed about a year ago in my basement. The installer left the wires sticking out of the wall for me to install a thermostat. He said if you want to turn the furnace on, just ...
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1answer
20 views

why does my gas furnace exhaust constantly

why does my high eff gas furnace exhaust run constantly ( when furnace isn't on ) the furnace turns on and off a few times before running then the blower comes on. now the exhaust wont stop without ...
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1answer
10 views

Gas frunace trouble shooting

Blower kicks on early and will only run 1 cycle. Have to turn down thermostat and turn it back up again to get furnace to come back on. It is gas.
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1answer
1k views

Where to connect a c-wire on a furnace with existing two wire mercury thermostat

My existing thermostat is an old mercury two wire device, heat only. Looking to upgrade to a better model, but I need to run a c-wire. I don't know where to connect the wire at at the furnace, any ...
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1answer
122 views

Connected C-Wire to new Smart Thermostat and Furnace board and still no power

I need help. I've been surfing the internet and have had no luck finding answers to my situation so am hoping for some guidance. I've seen other questions here answered but none that suit my ...
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1answer
12 views

Goodman gas burner not lighting

Goodman warm air gas furnace. Gas burner would not light.Status code light blinked continuously. Igniter glows red hot. I cleaned flame sensor with fine grade sand paper. Checked transformer line ...
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1answer
3k views

What could cause a Trane furnace to not start heating?

I have a newer (2007?) Trane XL90 (model: tdx2b080a9422aa)forced air gas furnace. The problem I am having is the burner and fan will not start. The thermostat is set at 67 degrees and shows it is ...
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1answer
42 views

What should I do after a low-voltage wire was cut putting the furnace door back on?

I have the basic Honeywell thermostat that a lot of people have. All the thermostat wires go to the blower in the attic (for the central air). They are spliced with wires that then go to the furnace. ...
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10answers
17k views

Do thermostat-controlled, auto-adjust HVAC vents exist?

The residential forced-air HVAC systems I have seen are controlled by a single thermostat in one room. One has to manually adjust the vents in order to adjust the temperature in other rooms. Is ...
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0answers
18 views

Limit switch failure

My XL80 trane failure! Limit switch SWT1258 fails at least twice a year now, first one lasted 10 years and then all replacements only last 3 to 10 months. Seems the switch is used too much but air ...
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1answer
48 views

Limit switch is good but no heat

I am getting a 4 blink indicator saying my limit switch is bad. I tested the switch and it is good. What else could it be?
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0answers
18 views

Why does my gas furnace run once then wont come back on until reset when temps are below 30 outside?

THE PROBLEM: My gas furnace will run one cycle and then not come back on until the switch is reset. Once the switch is reset it will kick on immediately run once and again I will have to reset before ...
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1answer
35 views

Can I replace my draft inducer blower with a model of a slightly different speed?

My furnaces draft inducer blower sounds like a snow blower running, so I set out to replace it. Finding a replacement part proved difficult, but I found a site advertising a compatible part and ...
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15 views

Would a frozen water pump hose for a furnace make the furnace run all the time?

Water pump for furnace and the water run to outside wall, the water hose was blocked and pump motor was dead. Can this cause the furnace (fan) run all the time cost more electricity.
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1answer
27k views

Why is my gas furnace now continually just blowing out cold air?

I had my heat set to 70°F all day and my gas furnace was blowing out warm air. Then out of nowhere, it started blowing out cold air for the past 3 hours. I tried turning off the furnace and ...
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2answers
614 views

What could cause a flame sensor to stop working so frequently?

Over a year ago after a month in our new house, we came back one evening to a cold home and after some googling, I found out that the flame sensor was dirty and the furnace was starting the flame and ...
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2answers
37 views

train xl 80 unit fires up then shuts right off

i have a train xl80 furnace. When it calls for heat the draft inducer fan turns on and then the burner fires up for a short time then shuts off then it starts all over again.I am thinking its the ...
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8answers
3k views

How can I audit my furnace?

I want to keep track of when my furnace is on, with an eye to reducing how much energy I use to heat my house. I could compare it with weather data (temperature, wind speed, precipitation). I could ...
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2answers
839 views

Wiggle, wiggle, wiggle wires on Furnace Pressure Switch makes it work — should I replace Switch?

My Furnace (a Rheem Criterion II Gas Furnace - model RGLH-07EAMGR) has had a problem for a while that we've just been living with but I can finally afford to do something about it. What happens is ...
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2answers
644 views

Why does my oil-furnace's on-demand water heater go tepid and then return to full heat?

We have an issue with the hot water from a 2004 Peerless oil furnace with on-demand hot water. The shower starts at full temp, but quickly goes tepid (too cool for a bath/shower, but not ice-cold) and ...
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0answers
20 views

Why would my Maytag FG6RC high efficiency furnace restart in the middle of a heating cycle?

My furnace is probably 7-8 years old, and this heating season the furnace has developed a strange problem. The furnace starts normally, but before the temperature reaches the thermostat setting the ...
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0answers
14 views

Why won't my furnace turn off after replacing the igniter?

My igniter on my Frigidaire furnace went out. before replacing it I reset a limit switch that set off. I changed the ignitor and everything works, however now the thermostat is not shutting it down at ...
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1answer
276 views

Condensation running down pipe connecting furnace thru ceiling to chimney

I had a new downflow 80% efficient furnace installed in 2006. I don't use it regularly as I normally heat my home with my woodstove (separate chimney). But I have used this new furnace many times ...
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2answers
106 views

How do I reduce the noise from my forced air furnace?

We recently had a new forced air furnace and return installed. The unit works great, but the return (which is in an adjacent closet to the furnace closet) is quite loud. What are some solutions I can ...
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3answers
162 views

How can I prevent my furnace and A/C from slamming doors?

What specifics will I need to collect to figure out if our furnace and A/C are sucking too much at the source/intake? I don't know the proper terminology for these things, do forgive me for any ...
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1answer
67 views

how do you manually turn on the gas to your house?

During an account switch our gas got turned off. The account is straight now but national grid goes on coffee break from 12am sat till 7am monday and for us, enough is enough. 3 family 3 story ...
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8 views

Goodman GM100 fails to recycle [duplicate]

Our Gm 100 Furnace fails occasionally to recycle after working fot a while. I have determined that something is becoming disconnected in the black terminal "box" on the gas valve. If I move the gray ...
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1answer
131 views

How do I check if this furnace switch the blower to second speed

My furnace is overheating and I suspect that the blower motor does not go into high speed. Can anybody say what is the cause or how can I check if it indeed switches to high speed? Here is the wiring ...
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3answers
25k views

How to wire multiple thermostats

I would like to have two thermostats controlling a single furnace. However I'm not 100% sure how I would need to wire everything to achieve the correct effect. Assuming a thermostat simply acts like ...
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3answers
1k views

Why does my furnace drip bucket fill up so frequently?

We have an oil furnace that heats the house using a two-zone hot-water circuit, and also acts as an on-demand hot water heater. There is a pipe coming off the collection of pipes coming out of it that ...