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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Replaced Thermostat, Furnace worked for 1 cycle now blows cold

Hello I just replaced my old White-Rodgers thermostat because it just wasn't working consistently (sometimes it would turn on the furnace, but mostly it wouldn't). I swapped it with a White-Rodgers ...
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32 views

Why won't my my furnace stop running unless I shut it off at the breaker?

I can't get my furnace to shut down unless I turn off the breaker. Why is this happening, and how do I fix it?
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18 views

Amana Furnace 90% eff. need help

Furnace will run for half a day to a day producing heat, then it will stop producing heat but the furnace will try to run still blowing air. Also, if I flip the switch off and then back on 10 seconds ...
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27 views

The thermostat is set at 73 however the furnace doesnot kick on until it is down to 67.

The 96 % goodman furnace was just installed. The service man changed the thermostat but I think her switched some of the wires. When I have it set at 73 it does not kick on until the tempature is ...
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6k views

Why would my Goodman gas furnace start but not stay on for more than 2-3 minutes?

I've got a problem with my 15 year old Goodman furnace. It starts w/o problem, inductor begins working, hot surface ignitor lights up and ignites the gas. Then the main blower starts working and the ...
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2answers
89 views

What is the smell coming through my HVAC system?

If I leave the furnace fan always running for an extended period of time (to circulate and filter the air), when the central AC turns on there is a not-so-fresh smell that is emitted through the ...
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3k views

How do I prevent harmonic resonance hum in PVC vent of newly installed hot water heater?

I just had a new power vented water heater installed (HTProducts Phoenix Light Duty) in our crawlspace. The contractor that put it in used part of the existing 3" concentric vent from the furnace we ...
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34 views

Why would a gas furnace shut down after 20-30 seconds?

I have an 18yo Lennox gas furnace (Modle 23G89). It starts and runs for 20-30 seconds then shuts off. The light blinks in a steady state- no code. Then I removed the filter to guarantee a clogged ...
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27k views

Why does my furnace need frequent power resets?

I have a NOMA Programmable thermostat attached to my furnace. The set point is usually around 21 degrees, and the room temperature is reading around 17 degrees. The furnace is not coming on. ...
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5 views

How to wire a Feeder Furnace?

I have a feeder oil furnace and I need to know how to wire the oil burner to the oil control box please help
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2answers
110 views

Wiring Aprilaire 700 Humidifier to York TG9* Furnace

I've read the related posts, but they don't answer my questions. Please, help! We had contractors installed: * Aprilaire-700 Humidifier with Auto/Manual Humidistat-Control Knob (non-digital) * ...
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30 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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78 views

Which furnace thermostats support variable swing/deadband?

My home furnace is currently controlled by a programmable Honeywell thermostat, but it regularly thrashes the furnace by turning the furnace on for just ten or twenty seconds. It seems that the ...
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53 views

Can I remove a furnace compartment vent that's obstructing roof repair?

There are two vents going up to our roof, one is the normal vent from the furnace exhaust straight up to the roof. But right next to it there's a second vent pipe, a little larger and single wall. ...
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53 views

HVAC system setup

I have a builder building me a home right now and we had agreed to set up two separate heating and cooling systems for the first floor and second floor of the house. I raised the issue the other day ...
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1k views

How can I stop my boiler from making all this noise?

I'd like to preface this post with the fact that I'm a complete diy amateur. I may say stupid things, or things that make no sense. Please feel free to correct me as I'm always open to learn. So, ...
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1k views

Why would said gas furnace keep shutting off?

Seems that I have a gas furnace that is having some sort of heat/air sensing issue. Basically it shuts off after running for a minute or two. But if I remove the top plate of the furnace itself it ...
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23 views

What can cause short life of the igniter in furnace?

what could cause short life of silicon nitride 80v,IGN00145.furnace trane xcm95 2years old put in 3rd igniter.
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1answer
59 views

Can a gas furnace be installed in an outdoor enclosure?

I have an old home in which ductwork has been retrofitted. The ducts for the first floor are arranged under the floor. The first floor is heated and cooled by an electric package unit sitting just ...
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1answer
94 views

Can you vent electric dryer into furnace return?

I've got an electric dryer currently vented outside: Behind the door to the right is our heat pump furnace: I was thinking about, during the winter, venting the dryer (properly filtered for lint) ...
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44 views

Furnace blower intermittently stops working

The blower on my furnace is set to be on constantly. The last two nights in a row I have woken up in the middle of the night to hear that the blower is not running and that the temperature is dropping ...
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2answers
101 views

How far should my wall be from my furnace/water heater?

) we are refinishing the basement and are enclosing the furnace/water heater, leaving a thin 27" door. My water heater sits back beside my furnace and the enclosure is going to be square so I think ...
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1answer
33 views

Why are my radiators leaking?

I have a gas boiler that seems to have way too much water in it and has pushed the excess water out the vents on my radiators. I have shut it off. It has flooded my main floor. How do I stop this?
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4answers
11k views

How do I wire an old furnace motor so I can use it as a garage exhaust fan?

Since last I posted, I moved WAY south (lil warm down here) and the house I moved into was a foreclosure so a few things needed done, namely the AC and furnace. When the guy did the job he said he ...
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2answers
62 views

How do I calculate how long a furnace has to work to compensate a given temp drop?

I am trying to understand the dynamics of heating a home after the furnace size was calculated. Say you have a 60000BTU furnace to heat a 2000 sqft home. At the beginning of the heating season you ...
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1answer
70 views

Is it normal for the burner in my furnace to turn on and off during a single heating cycle?

During the heating time when the furnace is running to reach the temperature ask for, the burners will run for 3.5 to 4 mins.than shut off for 1 min. Then turn on again.it will do this until temp. is ...
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1answer
142 views

Will a single ductless mini-split heat pump be able to distribute its air evenly throughout my ranch house?

I am in the middle of a deep energy retrofit of my house, and a quick-and-dirty online manual J calculation of the projected loads once my projects are completed shows an estimated heating and cooling ...
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1answer
2k views

gas furnace pilot light is lit,,won't produce heat, making a clicking sound,,,

my gas furnace isn't producing heat the pilot light is on and it's making a clicking sound what can I do? I've tapped the flame rod.
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208 views

How do I connect my whole house humidifier to my furnace?

Connecting Desert spring Humidifier to the furnace: Do I eliminate the 24V transformer that came with it? The furnace Keeprite has the the electronic board says Humidifier W1 and C. where can I ...
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3answers
252 views

Running computers in basement storage room safely

I have kinda an odd one. I'm mostly concerned about fire safety here and am not concerned about power, I already know how to handle that properly. I have a somewhat large basement with an unfinished ...
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2answers
59k views

How can I test whether my furnace issue is the limit switch or the thermostat?

I suspected this issue during the winter and confirmed it now in the summer. Regardless of the temp in my home, the blower motor runs non-stop. In the winter this must have been causing my home to got ...
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1answer
521 views

how to change furnace filter (bottom return) for Lennox G43UF

I have a Lennox G43UF furnace and I am not sure if I need to have both a filter for a side return and bottom return. If I do (which sounds logical), where would the location of the bottom return ...
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2answers
8k views

How do I test a furnace limit switch?

When my thermostat reaches the desired temperature, the furnace fan shuts off briefly, then cycles on and off a few times. Several internet posts pointed me to the limit switch, which seems to make ...
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2answers
340 views

How do I make my gas furnace throw out warmer air?

I just bought a new house. It has a 2007 gas furnace. The make is a 2007 heil furnace . I would like to know how to adjust the furnace to make it throw warmer air out of the ducts.
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1answer
151 views

Carrier 60,000 BTU 92% Furnace vs Carrier 40,000 BTU 95% AFCU Furnace

I have about 900 finished square feet in my house, and I'll eventually be adding another 200 or so finished sq/ft in my basement. I'm looking to get my furnace replaced and have been quoted two ...
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1answer
16k 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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27 views

What could cause the furnace to not come on after airing out the house?

Turned the furnace system off and manually turned fan on at the thermostat to air out the house after staining woodwork. Now the system is turned back to Heat and Auto Fan but will not cycle on. The ...
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34 views

How to clean carbon build-up on Honeywell whole house air purifier made of aluminum?

Bought a house recently that has a Honeywell F300 whole electric house air purifier/cleaner. The cell's aluminum fins have a black baked-on dust that I expect is preventing the unit from working as ...
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1answer
90 views

The hot water is working but the radiators will not heat up!

We have a Utica Boiler model number SFH4150WT and we are receiving hot water but the radiators do not heat up!!. We tried bleeding the radiators, they only heated up a little bit but after about 5 min ...
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39 views

What type of furnace vent pipe is this?

I need to extend my furnace vent pipe up 2 foot above the ridge of my roof to comply with IBC. So I need to couple this pipe somehow and extend it up. Any idea what type of pipe this is and how I ...
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3answers
5k views

Does a whole house humidifier go on the intake or outlet of the furnace?

On what side of the furnace do I install the tank of the humidifier (the warm side or the return air side)?
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2answers
8k views

Is my furnace operating normally?

I just moved into my house and I am wondering if this is normal for a furnace. So I have my furnace set to 68 degrees. The temperature on the thermostat says 66 degrees. The furnace is on, but does ...
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43 views

Testing the exhaust of a natural gas furnace?

I recently had maintenance performed on my natural gas forced-air furnace. During this maintenance, the technician went outside and used an electronic handheld device with a wire-attached probe to ...
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3answers
15k views

Adding a C wire to a new Honeywell WIfi Thermostat

I am trying to install a new Honeywell touchscreen WIFI thermostat and need to add a C wire to my terminal inside the furnace (using the help found at How can I add a "C" wire to my ...
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1answer
55 views

How do you troubleshoot a baseboard heater that is not heating up?

I have baseboard heat and we are not getting heat on one room. Can't bleed air from the baseboard itself. How do I troubleshoot the issue?
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1answer
106 views

Condensation at roof, down outside of furnace/water heater vent. What is happening?

I am getting condensation dripping down the outside face of my furnace vent at the roof. I think I know why this is happening I'm just curious how to remedy it. There is a cast iron exhaust pipe that ...
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145 views

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

I've read many posts on this, and believe I know what to do, but want to make sure. My furnace (a Lennox G14 Series) does not have a C terminal which needs to be connected to the C terminal in my new ...
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28 views

Identify/troubleshoot this millivolt furnace valve

I have an old millivolt gas furnace that's stopped working. The pilot stays lit fine and the thermopile generates about 360 millivolts, and there's no problem at the thermostat (checked voltage and ...
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2answers
261 views

furnace blower motor vibration when working hard

A few weeks ago my furnace developed a vibration that can be heard throughout the house. If I remove the side panel of the furnace or if I remove the filter, the vibration goes away. My theory is ...
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1answer
55 views

Possible to check NEST system compatibility by looking at current thermostat model?

I'd like to replace my Honeywell CT87A thermostat with a Nest thermostat. I see that Nest has a page to check system compatibility. Is it possible to identify if my system is compatible without taking ...