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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How can I prevent my furnace exhaust pipe from freezing?

My furnace keeps on turning off because my air intake freezes. The reason it freezes up is because my neighbors exhaust vent blows directly on it. What can I do to prevent this?
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1answer
244 views

What to do first in a house with poor thermal performance and high energy bills

I just moved into a house and am a little bit disappointed in its thermal performance so far. It's winter and cold outside, and the furnace heats the house up pretty quickly, but then the house gets ...
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1answer
132 views

What is this pipe - should I be worried?

We found it behind a wall, it is a bit more than 10 inches wide it has about an 3/4 inch of concrete between metal. It was jaggedly broke off on the bottom in the basement ceiling. It is also ...
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2answers
346 views

What could be causing my gas furnace to make a loud noise?

I have a comfort air natural gas furnace when it call for heat,their is a loud boom noise,could the hot surface ignitor have a crack or needs replacing?
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1answer
329 views

Furnace keeps resetting

My trane xr90 furnace keeps resetting just while it is in its "heat up phase" I'm a laymen but a description of what is happening is like this... The furnace gets a call for heat, it makes a sound ...
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2answers
1k views

Why doesn't the “fan on” mode work after I installed a new thermostat?

We moved into a new house. I installed a new Hunter Thermostat. I have a furnace only and the old thermostat only had 3 wires connected. SO I connected those three wires (G, RH and W/B). The ...
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2answers
353 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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121 views

Why won't a NEST that shares control of a furnace with a conventional thermostat turn on the heat?

I have three floors in my home. The bottom floor has its own gas furnace and the 2nd and 3rd floors share another gas furnace. Everything was working great until I added a NEST to the first and ...
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1answer
540 views

Which way should furnace filter face?

I replaced my furnace filter (every 30 days) but upon Googling, I've found it has to go certain way. It's suppose to go the way where the arrow points for the airflow. But my filters have no arrows on ...
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1answer
7k views

Forced air system blowing cold air through bedroom vents, hot through the rest

I'm in a rental house for the next few months which hasn't been particularly well maintained. It does have a newish looking Goodman gas furnace, yet the gas bills seem outrageous to me ($250 per month ...
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64 views

Can I use my forced air furnace to heat water for radiant heat too?

I moved from Europe to USA 4 years ago and I was wondering if it's possible to combine forced air heating with the heating that uses radiators. My idea is to use the furnace for forced air to heat up ...
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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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1answer
230 views

How close can an electric water heater and an electric furnace be to each other?

How close can an electric water heater and an electric furnace be to each other? My water heater is 7 inches from my furnace. I need 4 inches so that I can install a water softener and wash sink. So ...
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3answers
664 views

Should I leave the fan switch on my thermostat set to fan rather than auto?

I purchased a new Amanda Furnace in Oct'2013. I am told in order to maximize a warm, consistent room temperature I should set the thermostat to the Fan position rather than the Auto position. Does ...
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1answer
1k views

How do I connect a WiFi thermostat to my furnace's primary control?

I would like to install a Honeywell WiFi controlled thermostat to connect to a Honeywell R7184U primary control. My question concerns the "C" wire. The R7184 has the terminals labeled 1, 2, 3 and 4 ...
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2answers
2k views

Furnace flashing 4 times (Ducane)

My Ducane furnace flashes 4 times, runs for 5 minutes, and then the burner goes off. When the limit switch is jumped it runs good. What needs to be changed here?
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3answers
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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2answers
257 views

Would a failing igniter cause my furnace to blow cold air?

I noticed tonight my furnace was firing up, but not actually blowing out heat. I turned the thermostat down so it was no longer triggering it, let it sit for a couple of minutes, and then turned it ...
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0answers
114 views

How should I shut down a woodburner that is attached to an electric furnace for the night?

I have a Monarch Add-A-Furnace wood burner connected by ductwork to my Armstrong Air electric furnace. I use the wood burner when it gets really cold outside, but shut it down at night because I do ...
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2answers
663 views

Should I replace my Pressure Reducing Valve?

A few weeks ago, my oil-fired water boiler started continuously leaking water out of the pressure release valve on the top of the unit. I know this is leaking steadily because it drains into a 5gal ...
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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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3answers
633 views

Furnace installation

I have new 2 carrier infinity CNPVP high efficiency direct vent furnaces in my basement for my 3500 sf house. The air intakes for both units are not plumbed outside but instead are drawing air from ...
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1answer
309 views

What is this noise coming from my gas furnace?

Whenever I change my air filters in my furnace, I hear a boom noise. The last time I called DEER and they came out and fixed the problem (I can't remember what the part was called that was needed). It ...
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1answer
151 views

Legal requirements regarding 100% asbestos duct work [closed]

I am renting a condo. After starting the heater, dusty air came out of the registers, so I called out a company to clean the ducts. They verified the ducts are 100% asbestos and cannot be cleaned. ...
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4answers
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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3answers
7k views

How do I wire a humidifier without a 24 VAC IN terminal?

The instructions for the humidifier I'm installing says to connect the humidistat wiring to the two terminals "marked 24 VAC IN". My furnace doesn't have terminals marked that. I have R,C,W,Y.G. Am ...
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1answer
175 views

Can I install a flow through humidifier on either side of the duct?

I was about to install a Wait6000 whole home humidifier when I hit this snag in the plan. On page 3 of their manual (PDF), it says the cold air return duct must be at least 10" wide. The diagram ...
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1answer
6k views

How can I figure out why the low voltage furnace fuse blows on heat but not cool?

I have a Tempstar Model NTC6100KFG1 gas furnace. Furnace was working fine through the summer blowing the AC. It's been off for a month or two as we've been changing seasons here. When I went to turn ...
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2answers
20k views

What size breaker and wire do I need for central air conditioning?

I am getting ready to hang drywall in my basement but before I do that, I need to run wire from the main panel upstairs to the future location of the central AC furnace through the basement ceiling ...
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2answers
19k views

How do I identify the C terminal on my HVAC?

How do I identify the C terminal on an HVAC, furnace, or boiler? If the terminals don't have a screw labeled C what should I look for on the wiring diagram? What steps should I take if a wiring ...
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2answers
317 views

How do I close this hole in the HVAC vent?

What's the best way to close up this hole in the venting leaving the hvac? Would foil tape be sufficient? Right now it bleeds out hot air into the basement in the winter, and cold air in the summer. ...
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0answers
2k views

Why is my furnace limit tripping?

My furnace is tripping the high limit. It is a Downflow Payne 90+ have replaced the limit switch. I pulled the blower door off and checked all vents to ensure they are open and it still short cycles. ...
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1answer
5k views

Why does my pilot light go out when I release the pilot light knob?

My furnace pilot light will not stay lit. I can light it and depress the pilot switch for 2 minutes. But, once I let go of the button, the pilot immediately goes out. Does my thermocouple need ...
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2answers
785 views

Why doesn't my gas furnace ignite?

I had a Lennox slp98dfv installed last year - it has a surelight ignition - it now just blows cold air - so I assume the pilot light is out - but not sure how to light it - as u cannot manually ignite ...
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2answers
3k views

lennox furnace not working pilot light on but burner doesn't start

lennox furnace, model # G20Q2E-75-C1, serial #6392H32332, pilot light lights, blower motor turns on, burner doesn't burn
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1answer
1k views

Furnace won't adjust to thermostat setting

I have a 2007 Trane furnace that has been working the AC all summer just fine. With the cooler weather, when I turn on the heat and set the thermostat to 72 degrees, the furnace comes on but heats the ...
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3answers
7k views

Why isn't the spark gap lighting the pilot on my furnace?

I've got a Carrier 58GS natural draft furnace, which has a spark gap for igniting the pilot. Unfortunately, the spark gap has not been successfully doing its job. The spark clicks away as the gas ...
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1answer
552 views

How do I maintain an 80% efficient natural gas furnace?

I have an 80% efficient gas furnace at my house, that is seemingly working well and is configured with an air conditioner. What preventative maintenance should be done to it, and at what interval? Is ...
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2answers
2k views

Can I remove the fresh air supply that is attached next to my furnace?

It looks like my gas furnace is already vented but I'm not sure. There are two white pipes from the top of the furnace that are vented outside. The furnace is a Trane XR90. We have cold winter climate ...
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2answers
610 views

What is this name of this vent attachment next to my furnace?

What is the name of this silver vent attachment thing at the bottom of the picture? It is attached to the side of our gas furnace. The black part is an insulated air duct which goes to a vent ...
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1answer
222 views

Should I use a quick or gradual 90 in my flexible A/C ductwork?

To elaborate a bit more. If you are running an 8" duct off the supply, would you do a quick 90 degree towards the destination or do a gradual 90 degree? I would guess a quick would be better because ...
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1answer
245 views

Replacing Oil Furnace with Heat Pump

My wife and I would like to remove the older oil heat from our home and replace it with a heat pump. We currently have an Amana central air conditioning unit (3 ton), and an oil furnace in the ...
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1answer
2k views

Why is the circuit breaker for my furnace stuck in the off position?

The breaker for my furnace is stuck in the off position. We were away for the winter and had someone shut it off, and now the breaker won't turn on at all. We shut off the thermostat upstairs thinking ...
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1answer
369 views

What is a quieter alternative to gas forced air heating?

My small 1BR apartment has an old gas furnace that works great, but costs my landlord too much to insure. He plans to install gas forced air, an in-unit upright furnace. I'd love to suggest a ...
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2answers
858 views

How is a high altitude natural gas burner different?

What is the difference between high altitude natural gas burner and conventional low altitude gas burner and why high altitude natural gas burner are needed?
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1answer
22k views

Why is water collecting in the base of my furnace?

I changed my filter the other day and noticed a pool of water in the bottom of the furnace, below the filter. The humidifier has been off so that's not the issue. I removed the furnace panels and see ...
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1answer
151 views

Can a non-expandable filter be used in place of an EZ flex furnace filter?

My Carrier furnace has the EZ flex filters (16x25x5). These come with the plastic end caps that fit on the expandable filters. Can a regular filter, non expandable, of the same dimensions be used as ...
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2answers
435 views

How do I interpret my furnace clearance diagram?

My brother-in-law and I are going to be finishing my basement. We just got the permit from the building inspector. When they returned my plans there was a note that told me to make sure furnace and ...
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1answer
121 views

What to look for in a new furnace

I've recently been told that my furnace, which is about 20 years old, is on it's last stretch and that I should consider replacing it now rather than waiting for it to fail - potentially at a very ...
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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 ...