Questions tagged [furnace]

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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31 views

Advice on Furnace water leak, should I worry?

A week back we noticed our rug in front of the Furnace was soaked. Upon investigation I found that the leak appeared to be coming from a Vent Coupling (Vent Elbow) that leads out to our roof. I ...
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17 views

When switch furnace on, ventilation fan turns off

Ventilation fan works fine when heating is off but immediately switches off when heating is turned on. Consequently the furnace runs for a minute and then overheats and turns off. Any idea what could ...
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72 views

Which limit switch controls the blower motor on my furnace?

My blower motor isn't shutting off after my heat shuts off, causing it to blow cold air into my house. I suspect that the fan limit switch is bad, but the furnace has at least four limit switches. ...
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85 views

How do I add a filter to the return air vent of my retrofitted forced air system?

I have a 1940 home with a basement and a forced air heat pump system that was added some time in the past decade by the previous owner. The ceiling in the basement is open, and the ducts were ...
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115 views

Can't get furnace to run in FAN ONLY mode

I can't figure out why my furnace is not working in FAN ONLY mode. It works fine when calling for heat, but when Fan is set to ON and there is no call for heat (or heat is turned off) the fan does not ...
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16 views

Safe to install humidifier above furnace gas vent?

I'd like to add an AprilAire 600 bypass humidifier. I plan to install the humidifier on the supply plenum, and the bypass duct on the return air. The gas vent coming off the furnace is type B. ...
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191 views

Connected C-Wire (previously unused) to thermostat, but still no power?

In search of help with hooking up a Nest Thermostat E. I have seen several threads seeking solutions for similar issues and have troubleshooted with their proposed solutions with no luck. I am ...
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13 views

Goodman 080-4, propane… inducer fan runs non stop

The unit will go thru heat cycle when turning the power on. After the call to heat is met the inducer fan continues which prevents the ignition process upon the next call from the t- stat. It will ...
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14 views

Fixing sub-optimal Tempstar furnace vent installation but can't find part numbers

I have a Tempstar N9MSE0601714A furnace with 2" PCV vent pipes (that mate to 2.5" pipes). Whoever installed it didn't fallow the installation manual and I'm also reducing the number of ...
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34 views

Zoned Forced Air System Runs 2.5X Upstairs vs. Downstairs

I bought a house built in 2005, ~4100 sq. ft. Reasonably insulated to code, as required in Chicago, IL. I've got an upstairs thermostat and downstairs thermostat. Both are Nest thermostats ...
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47 views

Should furnace blower run when the heat is off?

Our furnace blower is set to auto....it runs when the furnace is and is not calling for heat but the humidifier is on. This is a problem because the forced hot air system is blowing cold air which ...
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165 views

How can I close a gap between ceiling drywall and a furnace flue?

My gas furnace is located in my laundry/utility and is normal(~80%?) efficiency with a Type B Flue. It goes up through the drywall ceiling into my attic(1 story) and out the roof and I verified that ...
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42 views

C-Wire for thermostat

My furnace is a gmp075-3 There is an existing unused Blue wire coming from the thermostat to the furnace area but not attached to anything. (upper blue wire in 2nd image) Can I just connect the upper ...
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54 views

Why is my furnace making grinding noises after thermostat replacement?

Replaced Lux (LTX9600) with Emerson Sensi thermostat. New Sensi thermostat will control heat but have unexpected behaviors like: when thermostat turn on and off heat there is a momentary grinding ...
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110 views

Furnace keeps going into lockout

My furnace has been going into lockout after several retry cycles. This happens about 30% of the time when we turn on our heat. We had a repair person who came over quite a while ago, and tested all ...
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81 views

Connecting blue “C” wire to gas furnace, but furnace already has white wire?

sorry if this is a stupid question but I'm trying to install a smart thermostat (Nest). I realized that while there was an unused blue "C" wire behind my old thermostat, it was not connected ...
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85 views

Gas Vent Pipe - Outside Placement

I Recently adjusted the exterior furnace gas vent pipe as per the picture below. The old placement ended where the first elbow (up/left looking at the pic) is currently. However given that my 2 year ...
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4k views

Can a furnace high limit switch be bypassed for testing, and is that dangerous?

A repairman recently found that the actuator and the high limit switches were not working when our 15+ Carrier gas furnace was only blowing cold air. There are separate thermostats for the downstairs ...
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29 views

Furnace often hums but not blowing air until resetting thermostat

Having a frequent problem with my furnace where I can hear it humming softly, yet no air is coming out of the registers and the house temperature slowly falls. It seems that this state can continue ...
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54 views

Gas furnace fails to fire up and provide heat

My gas furnace won't turn on when it's set to heat. My girlfriend and I both noticed that it was a little cold today. I went to flip the heat up a notch after dinner, and that's when I noticed that ...
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76 views

Does the combustion air inlet for a 95% HE furnace need to be sloped down the same degree as the exhaust?

I'm determining if existing 2.5" PVC furnace vent pipes can be moved inside an existing soffit box in my garage ceiling. To do this the exhaust outlet pipe could keep it's existing grade from ...
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24 views

Can I run my attic HVAC/Furance without an Air Cleaner/Purifier Filter

I have an Aprilaire 1410 air purifier attached to my attic HVAC/furnace. Does the air purifier serve the same purpose as a typical air filter in a HVAC/furnace or is it simply additional filtering? ...
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1answer
43 views

Furnace Not Running After First Cycle

My Trane XB90 model TUC060C936BA natural gas furnace will run without any apparent problems for its first cycle after being off for a while (several hours/overnight). From my non-expert understanding, ...
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38 views

Furnace: 4 flashes => open high limit

I have a Goodman gas furnace (GMH950453BXAE) that blows air but gas does not fire up. The circuit board light shows 4 flashes, which is open high limit. I've checked continuity of both high limit ...
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53 views

How can I prevent my instant on hot water heater from starving my furnace of gas?

How can I prevent my instant on hot water heater from starving my furnace of gas? Just installed a new tankless water heater. I have 1 inch gas line going to 3/4 inch gas line reduced to 5/8 gas line ...
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126 views

Help running a C wire from my furnace--no voltage from the C terminal on the circuit board

I am thinking about changing thermostats for my ICP END4X36T17A2 furnace, but my options are pretty limited due to my current thermostat hookup lacking a C wire. It currently has four wires hooked up ...
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316 views

Is my thermostat keeps losing power due to a furnace fault? [closed]

I suspect my furnace of reaching a temperature limit and cutting power to my thermostat as a result. How would I determine if that is the case? First off, my situation is very similar to Furnace turns ...
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1answer
35 views

Furnace won’t kick off once the desired temp is met

I had a Honeywell thermostat (older model), I replaced it with a new Honeywell basic model. Reason for replacing is because once I set the temp, and the temp was reached the furnace won’t kick off. ...
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80 views

I live in the Northeast area of the US, and my emergency heat on my furnace/ac is broken. Can I get thru the winter months without fixing it? [closed]

I live in the Northeast area of the US, and my emergency heat on my furnace/ac is broken. Can I get thru the winter months without fixing it?
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95 views

What can be safely attached to a gas furnace cabinet?

The gas furnace in my house is in my laundry room about 3 inches from a stacked washer and dryer. As such, my laundry room is short on space, so I had the thought I could add some organization by ...
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2answers
99 views

Venting a 96% furnace

I would like to use the existing exhaust ducting from a previous furnace to run the two pvc pipes for 96% furnace up through. I would cut the existing ducting in the attic to run the pvc out the roof. ...
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71 views

Force Furnace Blower to Run on Separate Schedule to Circulate Air

Appreciate any and all insights you might provide. I could tamper with this until I figured it out but I'm hoping that your collective expertise will save me some time and keep me safe! I've got an ...
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1answer
98 views

Goodman - C wire connection

I have an older unit Goodman furnace with a c-wire that isn't connected to the unit. In order to install a wifi thermostat to supply continuous power I need to connect the c wire. I see spots for the ...
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40 views

Can someone verify my wiring for Trane XE90 with Aprilair 600

I received my unit this morning and there was a diagram that says its better to wire the humidifier to the EAC, this way I run run the humidifier without running heat, which makes sense. Unit also ...
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2answers
144 views

Should burners be removed when fixing an overheating furnace?

UPDATE - INDUCER MOTOR DIED! Apologies for the long post again but would appreciate anyone's thoughts on my current furnace developments...at a minimum it would make for a good troubleshooting ...
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72 views

Two power sources on gas furnace?

I have recently purchased a home that has a high efficiency furnace in it. The previous owner had done some demo on an interior wall leaving a 2x4 with a switch on it. As well there is the usual turn ...
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124 views

Humidifier not keeping up with HRV

I just moved to an new (for us) house and we seem to not be able to keep the humidity up in the house. The house comes with a Heat Recovery Ventilator (HRV) that in the winter runs all the time on low ...
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188 views

Thermostat C-wire not working

I recently switched out my old thermostat for a new thermostat. The previous thermostat had an R, Y, W, G, and C wire. I plugged all of these wires into the same ports on my new thermostat. After ...
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170 views

Carrier Furnace Pilot light and Main Burner Flames out when main blower kicks in

Carrier furnace runs for about 3 minutes. Hot air comes out from vent for a minute or so it then turns off and kicks back on after 1 minute or so. I cannot find the model of the unit as the tag is so ...
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29 views

Where to connect common wire (no C terminal at furnace)

Trying to add a c wire for my nest thermostat and I have a free wire in the bundle (blue) but there isn't a c terminal at the furnace. I know there have been similar questions just want to ensure I ...
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34 views

HVAC Furnace blowing fuses

I'm having trouble with an older Nordyne HVAC unit. Current situation: Immediately after turning the unit on with a heat signal from the thermostat, the fuse on the control board blows. Most recently ...
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2answers
68 views

Can a marginal transformer be responsible for random standing pilot light cutoff?

I have an old (late-50s era) forced-air furnace system with a standing pilot. Over the past few years it's started randomly shutting off (an audible click occurs as though the thermocouple has cooled ...
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25 views

Bryant Furnace problem

I have a Bryant furnace model #355CAV060100 when the thermostat is set in heat mode and on auto the heat comes on but the blower fan runs in low speed. If i switch the selector on evolution thermostat ...
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131 views

Can I reduce temperature in one room on my hot water furnace based system?

We have a hot water baseboard furnace heating system. It all works well except for that one room gets way too hot if we are to keep temperature in all the other rooms. This particular room is the only ...
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1answer
110 views

Corroded wiring casing in basement - cause?

I just had our annual furnace tune-up and the guy who performed the inspection gave us a B tag violation because the electrical supply wire to our gas furnace is corroded and copper wiring is exposed. ...
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182 views

Winter damper setting for humidifiers [closed]

Problem: My brother has a drum humidifier on his furnace and is quite satisfied with it, so I installed one on my furnace this fall. He claims it is a good idea to partially close the damper for ...
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76 views

Does my heater have an air filter?

I just moved in here, and it's time to use the heater. But looks like there's no actual screw on it, and I cannot open it. As you can see in the pictures, looks like there's no filter as well. How ...
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58 views

What is this valve behind my furnace?

I have had trouble running my furnace. It keeps cycling on and off when running. I had this valve set to open when running the furnace. But recently I closed it and it seemed to run longer without it ...
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3answers
114 views

Why would outside air come out a furnace intake?

One of my furnace air intakes appears to be letting in fresh outside air. I have three intakes on the main floor and one in the basement. The basement one is the offender as far as I can tell. When ...
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26 views

Furnace blower sometimes won't come on

I have a gas-powered forced air furnace. The last time I had a repair man look at it, he said it's 30 years old, so it's getting harder to find replacement parts. It recently developed an intermittent ...

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