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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5
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2answers
21k views

Which way does air flow into a furnace?

Which way does air typically flow in a furnace? Put another way, does the filter usually sit before the incoming cool air reaches the burners or after? I'm trying to figure out which way the air flow ...
2
votes
1answer
16 views

What could cause the furnace blower to come on constantly and no fire in gas burner?

When thermostat is turned up on my hot air furnace, the blower immediately comes on, blowing no heat, had it checked and with some luck the burner fired after about 10 tries of switching on and off. ...
1
vote
1answer
21 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 ...
0
votes
1answer
29 views

How can I replace an old dial thermostat on an oil furnace with Hydrostat 3250 Plus?

I recently bought a home with an oil fired Biasi furnace that has a Hydrostat 3250-Plus attached. It uses an old analog round dial thermostat, and I'd like to replace it with a new digital (wifi) ...
3
votes
2answers
59 views

Can a furnace with a variable speed blower be used in a multistory house?

I just had an HVAC guy out to give me an estimate on a new Carrier Infinity series furnace and he said the second floor rooms will always be colder because the thermostat is on the first floor and not ...
1
vote
1answer
34 views

Could a high limit switch cause the furnace blower to run continuously?

My furnace was running fine. The I noticed that the unit was blowing cold air. Checked the furnace burners and they were off. I turned off the unit on the thermostat and the blower continued to run. ...
0
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0answers
9 views

ComfortMaker GUH075 series high-efficiency (93%) furnace isn't making heat

It worked a couple of days ago but today the fan blows but the burner doesn't seem to come on. The status indicator inside the access panel flashes four times but I can't find any reference to tell ...
2
votes
2answers
430 views

Furnace Draft Inducer Repair: is previously installed back plate necessary?

I'm replacing a non-functioning draft inducer on the Goodman furnace in my house (GMP075-3). The previous inducer was mounted with a sheet metal back plate between it and the wall of the furnace. ...
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0answers
84 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 ...
0
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0answers
12 views

Options for humidifier

Winter is approaching and the cool weather is making the air dry in our home. We're using room humidifiers but want to install a humidifier which can go on our furnace. However, we have very limited ...
0
votes
1answer
18k views

Why is my gas furnace blowing out cold air?

I had my heat set to 70°F all day and it was blowing out warm then out of nowhere, it started blowing out cold air for the past 3 hours. I tried turning off the furnace and turning it back on but ...
2
votes
1answer
3k views

Why won't my Heil 7000 natural gas furnace ignite?

I have a Heil 7000 gas furnace Model: NUGK100DH12 Serial: L933050100 When we turn it on at the thermostat, the exhaust blower will kick on. We checked to be sure the gas is reaching the unit and ...
1
vote
1answer
98 views

Can I relocate my furnace exhaust?

When my new furnace was installed, the vent was put outside the house next to landscaping bushes. It has killed one of my bushes. It used to be vented up to my roof and out. Can I move this outside ...
0
votes
1answer
43 views

What could cause the blower in my furnace to come on?

Ok my blower just turned on, my propane furnace and it's not in operation due it being summer. My thermostat is set at 65 and the room temp is 78. The heater never actually fired it was only the ...
0
votes
1answer
26 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 ...
0
votes
1answer
16 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, ...
5
votes
3answers
2k views

How can I avoid cold rooms due to combustion air intake?

I have a newer split level house (2006) with unfinished basement. The natural gas furnace is on the lower level in a utility room that is also laundry and bathroom. There's an enormous 8 or 10" pipe ...
2
votes
2answers
5k 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 ...
0
votes
1answer
43 views

Wiggle, wiggle, wiggle wires on Furnace Pressure Switch makes it work — should I replace Switch?

My Furnace (a Rheem Criterion II Gas Furnace - model RGLH-07EAMGR) has had a problem for a while that we've just been living with but I can finally afford to do something about it. What happens is ...
0
votes
1answer
50 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 ...
0
votes
1answer
23 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 ...
2
votes
1answer
29 views

How do I determine/control which heat source is used (heat pump, oil)

I have a heat pump and an oil furnace for backup. How does the HVAC system know when to use the heat pump and when to use the oil furnace? Specifics: I have a Honeywell TH8320U1008 thermostat ...
0
votes
1answer
272 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. ...
0
votes
0answers
72 views

Furnace not working properly with digital thermostat

I have been attempting to use several different types of digital thermostats to replace my old mercury thermostat, however none of them are able to control the furnace properly. All of them are able ...
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vote
0answers
58 views

Why is my furnace blower running at low speed?

My Payne gas furnace (PG8UAA 42091) automatically shuts down after it lights and burns for two minutes. It then gives a 33 fault code. I've done some research and some testing and have narrowed the ...
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vote
0answers
35 views

Furnace reset problem

I have a new Goodman high efficient furnace model number GMH950703BXAG1. And this is the problem I'm having now: Turn on the furnace power (after ~1 hour off) Turn on the thermostat with Temp ...
0
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0answers
27 views

Steps for annual maintenance on a fuel oil furnace?

We have fuel oil and this year I'd like to try and maintenance the furnace myself: By "maintenance" I mean "clean it up so that it runs well throughout the winter." Just a basic tuneup and ...
0
votes
1answer
78 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 ...
0
votes
0answers
22 views

Which should I do first? replacing furnace or resurfacing concrete floor?

I'm going to get two things done in my basement soon (by hiring professionals), but I'm wondering what the right order of operations is. One task is to replace the gas furnace that sits near the ...
3
votes
2answers
816 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 ...
7
votes
2answers
187 views

Why are furnace/central AC blowers so inefficient?

I can buy a ceiling fan from Home Depot capable of moving 5,000 CFM of air for about $50, and it uses a mere 50-60 watts while doing it. By contrast, most furnaces seem to have blowers that operate in ...
2
votes
1answer
54 views

Is it a problem that I have two of each color wires on my Honeywell thermostat?

I am thinking about upgrading my Honeywell thermostat. Every thing I have seen describes / shows a single wire for each color. My current thermostat has two wires connected to each terminal (two green ...
2
votes
3answers
8k 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 ...
7
votes
6answers
9k views

Where should my furnace filter go in a Lennox G40UHX series furnace?

I have a Lennox G40UH(X) series furnace, which is installed in our attic (We have a single-story house on a slab). Because the furnace is installed in the attic, it is "laying down" on its side, and ...
1
vote
2answers
5k views

Adding a C wire to a new Honeywell WIfi Thermostat

I am trying to install a new Honeywell touchscreen WIFI thermostat (http://www.homedepot.com/p/Honeywell-Wi-Fi-Smart-Thermostat-RTH9580WF/203926327?N=5yc1vZc5kl) and need to add a C wire to my ...
4
votes
3answers
2k views

Why does the pilot light go out when the furnace is running?

Every time the furnace fires up, it blows out the pilot light. Sometimes it will run a full cycle and blow out when it shuts down, and sometimes it will blow out about a minute into the cycle. We ...
2
votes
2answers
383 views

Are High End Furnace Filters worth the cost?

There are many levels of furnace filters. I can get cheap ones at walmart of a few bucks. Then there are ones that cost upwards of $30. I realize that if you have allergies or low immune systems, ...
4
votes
1answer
2k views

What would cause my furnace to only work with the filter removed?

My Carrier furnace works fine without the air filter in place on the return. With the filter in place it works for a while and then stops with a complaint about "limit, or flame rollout is open" ...
3
votes
2answers
2k views

What would cause a furnace to shut off prematurely?

I've got a Carrier Weathermaker 8000 furnace that shuts off about 90 seconds or so after ignition, started doing this recently. I get flashing code "33" which indicates: The code indicates: 33 ...
3
votes
2answers
412 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 ...
2
votes
1answer
3k 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 ...
0
votes
0answers
54 views

Why is my new high efficiency furnace blowing cold air sometimes?

Why does my new furnace high efficient Payne furnace blow cold air,not constantly but at least 3 different times in a day, my thermastat is set on auto but when the weather is cold outside it will ...
1
vote
0answers
68 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 ...
0
votes
1answer
34 views

Would a radiant barrier help stop this heat transfer?

Using my nifty thermal camera, I discovered that my furnace closet's combustion air duct (visible in this question) is getting really hot when the attic heats up, and then (being sheet metal) it ...
1
vote
1answer
65 views

Why does my Thermo Pride oil furnace need constant restarts?

We have a Thermo Pride oil furnace that requires frequent restarts to run. We just purchased the house and had the annual service/safety check completed as it was neglected for several years. When the ...
0
votes
1answer
32 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.
9
votes
9answers
11k views

Do thermostat-controlled, auto-adjust HVAC vents exist?

The residential forced-air HVAC systems I have seen are controlled by a single thermostat in one room. One has to manually adjust the vents in order to adjust the temperature in other rooms. Is ...
2
votes
1answer
145 views

Can I properly install Roxul mineral wool batts in a mostly-drywalled stud bay by pushing them up from below?

Using my nifty thermal camera, I discovered that my furnace closet's combustion air duct (visible in this question) is getting really hot when the attic heats up, and then (being sheet metal) it ...
0
votes
1answer
77 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.
7
votes
2answers
939 views

Should I insulate steam pipes in the basement?

I have a steam-radiator heating system. The furnace is in the (unfinished) basement, and the steam-carrying steel pipes spread out across the basement ceiling before going up into the rest of the ...