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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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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2answers
71 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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1answer
336 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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1answer
136 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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1answer
273 views

Does the pilot flame of a gas furnace stay on for the duration of a heating cycle?

I was looking at my furnace a couple of days ago and I notice one thing: there is something red hot there where the spark igniter and the thermocouple assembly is. I can hardly see it and I am not ...
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1answer
55 views

If flame sensor will affect Motor assembly's functionality of furnace? How does that work? [closed]

I have two Air conditioning company. A is the self-hired for my A/C, and B is assigned by home warranty company. This summer, the technician with A came out for an annual maintenance on both A/C and ...
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1answer
3k 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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3answers
2k 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 ...
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1answer
204 views

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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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
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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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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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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2answers
267 views

Furnace control board - interchangeable?

A few months ago, I had someone working on my outdoor a/c unit, and he accidentally shorted out the control board in the furnace (it's a Goodman gas furnace GKS91155DX). He replaced the board, and the ...
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1answer
147 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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1answer
19 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
27 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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1answer
86 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
75 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
283 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
64 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 ...
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3answers
153 views

My furnace cycles once, then won't ignite again. What could be wrong?

My furnace is not working properly. I shut down the whole electricity and also the switch on my furnice and waiting a few minutes to turn all back on. It will heat up the house and turns off ...
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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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1answer
54 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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1answer
109 views

wiring furnace draft inducer fan

I replaced a draft inducer fan on my furnace, the two wires in the furnace that connected to the old fan are black and white. The wires from the new fan are both black. How do I know which to connect ...
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1answer
70 views

A professional to test asbestos safety in furnace ducts

We live in a rented house with an old furnace duct system (probably 1960's). There is asbestos-containing duct-wrap all around the ducts, and it starts to crumble in some places (it's located in the ...
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1answer
174 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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1answer
72 views

What temperatures are normal in this area of my furnace?

Please see the attached picture and pay attention to the "temperature dial" in the inset With the current settings the gas burner cycles like this -limit temperature 200F -at that temperature the ...
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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
140 views

Heating system won't blow warm air

Turn my heat on via the thermostat. My oil fed burner kicks on and is lit up (heat is being made). The system is sucking in air to feed the system. Only problem is hot air never makes it out the ...
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1answer
130 views

What could cause a mobile home furnace not to light?

Our furnace won't lite. Mobile home pre 80. There is no name that we can see. The pilot light piece looks to be changed. Pilot light won't light. We don't hear or smell gas. It has settings last, 2, ...
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1answer
3k views

Why is my water expansion tank leaking?

I live in the northeastern US and we just turned the heat on (oil) and this morning I went down to the basement and saw this: The water is coming from the plumping above something labeled "water ...
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1answer
313 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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1answer
678 views

Which terminal should be used for a ā€œCā€ wire when none are labeled ā€œCā€? Older electric furnace/heat pump

I have an all electric air handler/furnace connected to a separate AC unit and it is also a heat pump. I've purchased the latest and greatest Honeywell WiFi "Smart" Thermostat and it needs a C wire. ...
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2answers
708 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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1answer
623 views

I have just reset furnace due to a trouble code, what should I monitor or re-do over the next few days?

My furnace was throwing a trouble code. The code was 31 and for my manufacturer (Bryant) and others thats is a pressure switch code. I was able to resolve this code and get my heat back on simply by ...
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1answer
58 views

Furace fuse blows when Aprilaire humdifier is turned on above 35%

I live in a pretty old house and have a Carrier furnace with an Aprilaire humidifier attached to it. The device that controls the water flow, I guess it's a solenoid, is visible on the exterior of ...
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1answer
220 views

Water has quit running thru my humidifier.

Furnace humidifier dry as a bone. have changed the filter, duh, that is the only thing I know how to do! Bottom line, there is no water running through it.
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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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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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1answer
539 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
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
630 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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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
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
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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1answer
120 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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0answers
22 views

Why would a blower motor work with A/C, but burn out with furnace?

I've gone through 2 blower motors since I purchased the home 3 yrs ago. I never have an issue with the blower when the AC runs; but it keeps dying in the winter with the furnace. I've had 2 HVAC ...