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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Advice on how to wire a 4 wire RGWY wifi thermostat to an old hvac with no c wire?

I have a 4 wire RGWY coming out of the wall to my old thermostat with no additional wire available for c wire. I was going to use the green one instead as I saw a tutorial online, but when I got to ...
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HE furnace exhaust options

Can i use two existing 2" PVC pipes from old furnace and tie them together with a Y connection going to the exhaust of a new furnace that requires 3" exhaust? New Furnace is 100,000 btu. 2” ...
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Is 2 stage furnace worth it in dual fuel setup?

I am replacing a gas furnace with AC unit with a gas + heat pump system. Looking at 2 stage furnaces I was left to wonder if its advantages hold in that setup. If gas is only used for temperature ...
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How to estimate and compare operating costs of gas vs electric furnace?

My home has an old electric, central furnace. All of my neighbors are on natural gas. I pay 5-6 times as much as they do on my heating bills during winter months. I can either convert my home to ...
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Where do I connect my common wire (C wire) for smart thermostat?

I've been running 2 Nest thermostats (1 upstairs, 1 downstairs) for years that didn't require a common wire. I'm replacing them now with Ecobee3 Lite thermostats. Both thermostats control heat from ...
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Junction box for furnace fuse reads hot with NCVT, but the furnace operates normally. Is this dangerous or incorrect?

Location: United States, Colorado While diagnosing an unrelated electrical issue during renovation, I discovered that the junction box containing a fuse and switch, which provides power to my furnace, ...
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Can a blown furnace transformer cause "hot spots" on the furnace circuit board?

We had a/c installed yesterday. The technicians had to pull out then re-install the furnace. In the process, they blew the furnace transformer. They also showed me some "hot spots" on the ...
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Help with installing Google Nest thermostat

I have a Google Nest I want to install and I saw there was an unhooked blue wire at both ends, so no big deal right? Wrong, apparently. What the heck? We have a Climatrol 170-1-080-02-00 furnace and a ...
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Furnace doesn’t have a c wire and or board

Have an old Colman unit in a modular home, needing to hook up c wire adapter. Does not have a circuit board. Any help on trying to hook up c wire would be great. Tried loading photo but will not let ...
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Water heater flue and fresh air intake letting in pests

The heater is in a closet in hallway. The flue is going up into attic. Attic insulation 3 yrs ago filled duct (pink insulation). Placed bug traps in closet, nothing 1st year. Lived in place 7 years ...
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Bryant 926TA “Continuous” fan speed really slow

I have a Bryant 926TA furnace with AC unit. System runs fine but if I run on “continuous fan” on the thermostat (so fan/blower always runs even if not calling for heat or cooling) the fan changes ...
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Does my high efficiency furnace need two sources of outside air

I had a high efficiency furnace installed. It has a pipe leading to outside for intake. My old furnace had a vent to take air into the firebox. Can I now block that vent since the new furnace has its ...
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1 answer
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Is it safe or even code to place a furnace on top of a main water line?

This is a new build. Builders have allowed this but I anticipate if I ever have a problem it will be a complete disaster. The furnace is sitting on top of the main water line coming out of the cement ...
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No Power To Humidifier

Hoping an expert here can help me out with an issue. I have a Goodman GMV9/GCV9 furnace and a General Aire 1042-L humidifier. When I went to replace the filter for the humidifier, I noticed it was dry ...
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Can I connect a C wire to enable a furnace fan?

Hot weather is here and we don't have AC in our rental house, but our thermostat does have the fan option. After searching online, and seeing other solutions, I decided to look into our setup. All ...
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1 answer
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Lennox Wiring for Ecobee SmartThermostat

Confused by the wiring, hope someone can help me out. At the furnace there's only four wires in the cable (R, B, G, and W), but at the other end, a yellow wire appears. It's not reflected in the ...
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1 answer
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Is it possible that Thermostat Y wire and C wire is the same wire on my air handler (furnace)?

I'm trying to install Ecobee, and like many others, I do not have C wire at the thermostat, thus need to find it on my air handler. My air handler is from Allstyle and the model number is HFD36-42840G-...
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My apartment uses a gas furnace. The gas technician shut off the gas to the furnace stating that "the return air box not sealed"

We had a gas service interruption the other day. When the gas technician come by to turn on the service, he noticed that the gas furnace had "holes". He then shut off the gas to the furnace ...
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2 answers
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Musty smell from furnace

When switching from cooling to heating in the fall we get about 2-3 days of musty air and then it's fine all winter. It's like wet sock/sneaker smell. Yesterday, the A/C kicked on because our house ...
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1 vote
1 answer
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Can I add an extension to an air intake for apartment central A/C? Is this a health or code violation?

The apartment I am living in has a nasty odor coming from underneath the furnace/ac and water heater. The air for the furnace is sucked up from this underneath section making all of the air that is ...
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Rhythmic tapping/banging sound on the external AC unit coupled with transformers in the furnace blowing out

We have a strange issue. We bought a house recently. We have several issues: External AC unit keeps making banging sound when heat is on The HVAC furnace stop functioning. In the last 6 months we ...
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Utility closet mystery sound

Background Hi StackExchange. I live on the third floor of a four-floor apartment building, wherein the ground floor is a currently-unoccupied commercial space and there are six total residential units ...
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How can I diagnose why my oil burner is not coming on?

I have a Buderus oil furnace with a Riello burner and Hydrostat controller and it does not appear to be coming on when it should. For example, right now the controller has the green dot lit, which ...
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Black tar-like stucky subtance leaking slowly building/leaking from furnace pipe

Could someone please tell me what this substance is that is leaking from my furnace pipe? It seems to be coming from the gasket area (see pictures). Thank youenter image description here
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Trane Furnace not starting in freezing rain - three flashes

I have a Trane hot air furnace that has recently become temperamental with freezing rain or snow contaminating the air supply. Can humidity in the air supply interfere with its operation? In new ...
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C wire confusion

I have an old thermostat (20 + yrs old) that I want to replace with a Sensi smart thermostat. My furnace has a dull pink looking wire connected to the W terminal (also connected to the W on the old ...
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2 answers
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Furnace making a loud cracking noise when starting

My furnace has started making a loud cracking noise when it starts up. It still seems to be working, as far as I can tell, and the noise does not happen after the furnace lights up. I made a recording ...
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Wiring New Honeywell RTH6580WF Thermostat with no Yellow Wire at Thermostat

I am Wiring a New Honeywell RTH6580WF Thermostat but there is no Yellow Wire at Thermostat. The old Trane thermostat only had 4 connections and the blue (C wire) was connected to the Y terminal. The ...
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1 vote
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Trane BLU068-A1 Furnace not heating

I have a Trane BLU068-A1 furnace that will not "heat" (the fan will run) on its own. I "can" get the furnace to heat by using a long bbq lighter and lighting the pilot light ...
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1 answer
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Goodman furnace triggering pressure switch error after running for 20+ minutes

My inducer motor bearing was making a ton of noise and likely about to go out so I replaced it. After installing the new inducer motor my furnace will run for 20 to 30 minutes and then throw a ...
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1 vote
1 answer
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Did I wire this furnace correctly?

I'm planning on connecting a nest thermostat in the next few days once my wifi is hooked up. In the meantime, I found an unused blue wire at the furnace and hooked it up to the C. My current ...
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1 vote
2 answers
192 views

Can I use this unused blue wire as my C wire for my new Nest thermostat?

I am a bit confused with my furnace wires. I did some research and watched a bunch of YouTube videos on how to install the Nest thermostat. I currently have a normal digital Honeywell thermostat. I ...
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1 vote
2 answers
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Am I missing accessories to properly mount filter in my Carrier Infinity gas furnace?

Our Carrier Infinity gas furnace (model 59MN7A080V) was installed more than 10 years ago. I have only recently taken over as "manager" of the furnace and have no clue how to properly install ...
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1 answer
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What are these pipes sticking out of the ground and foundation wall?

The following pictures are from a 1930s home, which was initially heated with charcoal, then converted to oil, and then converted to natural gas. The previous owner who did the conversion from oil to ...
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1 vote
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Lennox G40UH erratic behaviour

I've spent the last couple of days troubleshooting my Lennox G40UH furnace. A couple of weeks ago, I noticed that the furnace would sometimes come on briefly (anywhere from one second to a couple of ...
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1 answer
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Furnace pilot kicks on and then 'gushes' gas making a huge flame, kicks off and comes back on

Blower kicks on and runs for a few minutes before Gas comes on and everything is normal and then the flame 'gushes' gas and you can see bright flame inside it (while cover is on) and then it goes back ...
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How can I determine which furnace draft inducer is a compatible replacement?

I'm replacing my draft inducer / booster and I'm not sure how to find a suitable upgrade and from what I have found this seems to be the exact part FASCO A985 (7085-1124, 330701`-701FA). Is this ...
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Furnace will occasionally not turn on unless thermostat temp is increased

Occasionally (mostly in the morning) my furnace will not turn on. I have it set to 72. When I wake up the house temperature has dropped to say 64 or 65. If I turn the thermostat up to say 74, the ...
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Why is there shimmery white dust coming from my floor vents?

There is a white dust settling around all of my downstairs floor vents. It’s got a shimmer to it. I haven’t noticed it upstairs coming from the ceiling vents. We had all new HVAC done a year ago when ...
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Lennox 80mgf3-75a-3 furnace 4 flashes of one LED after gas burns, takes forever to heat

I have a Lennox 80mgf3-75a-3. Here is how it is operating: Thermostat sends signal Gas burners come on in about 20 seconds (LED flashes slowly and simultaneously - furnace has only one LED ) Then ...
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Why vent on first floor blows cold air mostly and hot air sometimes?

My house has 3 floors and gas furnace is on 3rd floor. First floor has total of 3 vents but one of those blows cold air most of the time and hot air rarely. The other 2 vents on the same floor blows ...
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Overheating/airflow issue with gas furnace: 3 different HVAC techs, 3 different diagnoses

I'm a new homeowner (1.5 years), and there was a new gas furnace installed just before we moved in. A month or so ago, the furnace started making a whistling noise for a second or two just at the ...
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how to meter natural gas usage in a part of the home

I rent my basement out. It's currently heated via electricity. It's cold where I live, and my renter's electric bills are high. I'm thinking of installing a natural gas wall furnace in the basement. ...
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1 vote
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Water dripping from a gas vent thats connected to my furnace

I just noticed when I opened the closet where my furnace is located there was water in the middle. It appears to be leaking from 2 spots on a vent that's labeled the (gas vent connector) its sunday ...
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1 vote
1 answer
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Would it be dangerous to tap an existing flame sensor circuit to create a common connection for my thermostat?

I'm considering using this answer to connect a common wire to my thermostat. I have the exact same setup, and have verified with my multimiter that the red T terminal outside F terminal beeps, while ...
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Pilot light goes off when depressing button ; new thermopile / vent switch

I have a Empire GWT-35-2 wall heater, when the thermostat would kick it on, it would turn off before reaching target temp. Would light and this would repeat until recently I can't get the pilot light ...
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Bryant 355 furnace not heating

My furnace runs and trips roll out without blowing warm air, I suspect the inducer isn't running fast enough. I watch it kick on and the inducer runs fast but right when it lights the inducer slows ...
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Is DIYing a replacement of Electric Furnace and Air conditioner worth it?

My Air conditioner does not produce cold air, however heater part in Furnace works just fine. Air conditoner Unit is at least 20 years old and have no coolent left in the system. I am looking to ...
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Replacing 1-Stage Furnace & A/C for Comfort & Efficiency

Need opinions on imminent HVAC work in a Massachusetts home. House and HVAC system descriptions below: House: ~45yrs, 1850 sqft, 2 floors + unfinished basement (furnace located in basement). Each ...
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-1 votes
1 answer
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Possible to "soundproof"/reduce noise from First Floor Furnace/AC?

We have a 1080 sq. ft., 1-floor (no basement) house. Our furnace and cold air/AC returns/registers are literally almost in the living room/main sitting area and it's very loud year round, making for a ...
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