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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91 views

Fan comes on but the air conditioner does not

During hot days when the air conditioner is on a lot it comes to a point in the evening when the air conditioner shuts down and the fan (from furnace) stays on. This will go on all night as the house ...
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38 views

How do I wire a furnace fan that has an electronic control module to run at full speed?

It is very useful to have an old furnace blower hanging around. Attach a plug a move lots of air. (Don't do this at home because it's much to useful and fun). The motor is a GE ECM Motors Model ...
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1answer
40 views

Low voltage over C wire at thermostat

Similarly to this question of the same name, I am reading low voltage over the R,C wires at the thermostat. Unlike that question, however, the voltage is unusably low. I am only reading 2V over R,C ...
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Identify HW aquastat and add common wire to Honeywell aquastat

This has been asked before, but I can't find any info on my Honeywell aquastat. The model number, normally on the inside paper on inside of cover, is missing so I do not have any model number. There ...
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1answer
32 views

Can I put steam humidifier nozzle above the AC coils

I'm trying to understand how the AC coils drain the condensation. I have installed a steam humidifier and connected to the top plenum above the furnace and AC coils. My worries are if the steam will ...
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2answers
37 views

If I build walls surrounding sump pump, water heater, furnace, A/C, will it work stopping flood water from spreading to entire basement?

In the past, my basement was flooded twice. Both of which where lower than 8". I'm wondering if the following works to prevent future flooding of my basement or stop water from spreading to the ...
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1answer
78 views

What is this opening in the ceiling above my furnace, and can I plug it?

I recently installed a whole house fan in my attic. For those unfamiliar with whole house fans, they work by creating negative pressure in the living area and positive pressure in the attic. This ...
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4answers
7k views

Does my furnace suck air from outside?

I've tried Googling this but the stakes are quite high and I don't want to be wrong, so I'm asking here. Wildfires are raging in California where we live, and the Air Quality is nearing the 'hazardous'...
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2k views

No power in r line after changed thermostat

I have a carrier furnace 2008, just changed my old thermostat to new nest thermostat, forgot to turn off the power. Now I have no power on my r line, checked short fuse still good, red light in front ...
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2answers
49 views

Installing c wire in older furnace

I just installed a nest thermostat and need to hookup the c wire inside the furnace. I read where you need to connect the c wire to the secondary wire on the 24v side of the transformer. There are 2 ...
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1answer
210 views

Why would my Maytag FG6RC high efficiency furnace restart in the middle of a heating cycle?

My furnace is probably 7-8 years old, and this heating season the furnace has developed a strange problem. The furnace starts normally, but before the temperature reaches the thermostat setting the ...
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1answer
68 views

Adding split AC to a Dayton oil fired forced hot air furnace

I'm trying to add split central air to my Dayton oil fired forced hot air furnace, mod # 3E268A. The manual clearly says it can accept this but the terminal block in the unit only has (4) lugs. TT and ...
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2answers
499 views

Furnace Blower fan doesn't start

I have a keeprite high efficiency furnace that Was a part of my new house. It's 2016. The Honeywell thermostat is set at 23 deg C. This is what happens when the temperature is below the cut-off I ...
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67 views

How to determine the right MERV rating for Carrier furnace?

I have a Carrier 59SC2B. My research so far suggests that I need to measure the air pressure with a manometer at the return and supply side and add them up. Then use the table supplied with the ...
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57 views

Blower fan comes on once a week

I have basic two wire thermostat, one for power on for neutral. I only have central heat, not air. My blower fan kicked on the last two sundays, but itself, but not today which is sunday. It only ...
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2answers
84 views

Attic HVAC BTU considerations

I live in central New York and will be installing a furnace and coil in my unfinished attic with an A/C unit outside to condition 800 sq/ft of upstairs living space. The attic a standard overhang (no ...
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92 views

Hooking up AC compressor to an old Lennox furnace

I'm trying to connect an ac compressor to an old Lennox G12Q3-110-3 furnace. Tried it a couple of ways and can either get the compressor to turn on or the furnace fan. Not both. Any ideas on how to ...
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1answer
38 views

Furnace Inducer Whirrs on and off before igniting, works when I tap circuit board

My furnace gets the signal from the thermostat, then about half of the time, the inducer motor whirrs on and off over and over. Sometimes it runs continuously without ever lighting. When I open it up,...
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53 views

HVAC / Furnace Evaporator unit in attic leaking cold air

We have an A/C (and heat) unit in the attic with force air ducts going to the ceilings in the rooms. I was in the attic today when the A/C turned on. I felt cold air come on my leg when I was near the ...
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81 views

Black sticky goo coming from furnace

Can anyone tell me what this is coming out of the furnace....
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154 views

Connecting fresh-air damper to Lennox furnace OR replacing timer with new smart thermostat

We replaced a 20-year-old furnace with a new Lennox furnace and added air conditioning. The new system is still controlled by the 20-year-old Honeywell Chronotherm III thermostat. The furnace had (and ...
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2answers
138 views

Is there a reason to replace 50 year old metal ducting in the crawlspace with modern insulated flexible ducting?

My concern is heat loss in the chilly crawlspace. No AC here, only forced air gas furnace. The existing metal ducting in the crawl space is over 50 years but is intact. There is a very thin layer of ...
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1answer
88 views

Trane Furnace Fan Works, But Heater Won't Run

As stated, my heat isn't coming on. When this started: Everything has been all fine and dandy all winter. The other day I ran the fan only for a few hours without the heat. After this, my heat ...
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1answer
122 views

Furnace Short Cycling

My furnace is short-cycling. I've tried the following: replaced the flame sensor Shorted the thermostat heat demand signal Checked the blower capacitor Checked the air intake filter Checked the ...
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1answer
60 views

How can we connect a smart thermostat to our heating system, which is a gas furnace and wood fireplace?

We have a KozyHeat wood fireplace connected to our older gas furnace. The idea is that the furnace serves as a fan when the fireplace is hot, or will use gas to heat the house if the fireplace is cold....
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44 views

heat is not responding to thermostat set temp but comes on when turned off and back on with the thermostat switch

At times during the day my gas burner doesn't try to come back up to the set temperature on the upstairs or downstairs main thermostat. I'll hit the up button a couple of degrees but no change. Then ...
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68 views

How to estimate the right size furnace for my house

I estimated the BTU for a new furnace for my house to be around 62,000 BTU. My Trane XR 90 furnace is 80,000 BTU. The square footage of my house is 1040 sq ft. Is a furnace over 18,000 BTU overkill ...
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287 views

Run Only The furnace fan

I have an old unit that has no control board. It works with a sequencer. (Coleman 3500A816) is it possible to wire it up to to be able to call only the blower to come on and not the heat as well? !
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3answers
52 views

Gas fired Forced-air furnace has a outlet grill in the mechanical room - can I remove it?

I just moved into a house with a gas fired forced-air furnace. Whenever I'm in the basement and the furnace is running I can hear a whistling noise coming from the mechanical room. I traced this sound ...
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1answer
48 views

How can I control my furnace fan from a secondary thermostat?

I have a WaterFurnace geothermal system with upper and lower level zones. I recently added an outdoor wood burner and my issue is that I want to use a secondary stat to run the furnace fan during the ...
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1answer
408 views

HVAC York diamond 80 furnace A/C

So I have a York diamond 80 furnace and the motherboard burned out so Lowe’s came and replaced it. I’ve been using the heater because it’s winter right now but the other day I accidentally hit the ...
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1answer
1k views

Furnace not heating after changing thermostat

I have an ancient furnace/AC combo that came with my apartment that originally came with a very simple battery powered thermostat, which I replaced with a modern Honeywell programmable wifi thermostat....
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1answer
1k views

Sticky black liquid coming from Furnace / AC Unit

I have this sticky black liquid slowly leaking from my gas furnace / ac unit. I called an HVAC repairman and he wasn’t sure what it was. He said he thinks it’s an old drip pan made of tar (not sure ...
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1answer
100 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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1answer
1k views

Furnace Connect G Wire

I have a dual energy electric/oil furnace that is wired to a thermostat with 2 wires R and W. I don't have any AC. Inside the furnace there is a switch relay to control the fan but it is not connected ...
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1answer
233 views

Line to AC dripping at the furnace

My line from my exterior AC unit is dripping at the furnace. The dripping over time has caused rusting and we've had to replace the control board under it. It appears the root cause of the problem ...
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2answers
56 views

I need a C wire connection for my new Glas thermostat

I have 3 wires(red,white,and green) going to my thermostat. I’m replacing my old thermostat with a new one the requires a C wire connection. The 3 wires goes to my Honeywell aquastat. The white goes ...
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2k views

Where to add a c-wire on my Goodman furnace?

I'm looking to upgrade my old thermostat and need to run a c-wire. Where would be the best place to tap into?
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58 views

For a smart thermostat, where do I attach the C wire to my furnace?

I know I've seen several questions out there about getting a C wire for a smart thermostat, however after all the research I've done and people who have given me guidance so far I have still had no ...
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4answers
134 views

Practical ways to reduce rattling noise in furnace?

Our bedroom is right above where the furnace is in our rented apartment. The furnace below makes a lot of noise, especially a rattling noise. Landlord is refusing to take any actions on it saying it ...
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1answer
62 views

Empire Wall Furnace Blower Problem

I have 35,000 BTU wall furnace with a blower motor. When the furnace heats up, the blower starts for about 2 or 3 seconds, turns off for about 5 seconds, then back on for 5 or 6 seconds, then off for ...
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1answer
10k views

Goodman gas furnace limit switch opening, blower only runs with a/c

I apologize in advance for some of my incorrect terminology. My father has a 2004 Goodman GMH80904BN gas furnace with a/c. The a/c has functioned properly all summer here in Ohio, we have recently had ...
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67k views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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1answer
7k 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 ...
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1answer
21 views

Attic Fan for Carrier 58STX110--14122

I have a Carrier furnace in my attic (Model 58STX110--14122). Does this unit include an attic fan? There is a fan that used to turn on during the day when it's hot and turns off when temperatures ...
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1answer
316 views

Furnace draft inducer switch tripping

I have an older furnace and a brand new natural gas instant water heater that I installed. I only start this way because the furnace had one thing break last year, so I'm not sure if things on it are ...
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2k views

What is this electrical fixture above a natural gas fired forced air furnace?

While visiting my mother-in-law, we wanted to get the smoke detector situation in her house up to par (this is in Massachusetts, we're from Europe, though). She has a natural gas fired forced air ...
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7k views

Where to attach the c-wire inside Goodman GMP100-4 Furnace

As a relatively new home-owner, I recently came across the whole C-wire issue for the first time, having had to recently replace an old thermostat, and there is no C-wire connected inside the furnace. ...
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1answer
101 views

burners out of sequence with blower motor

I have a Bryant furnace plus 90 model #398AAW036060D. I just changed the blower motor. In the last five years I've changed the main board, inducer board, pressure switch, and cleaned the igniter the ...
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434 views

My blower fan won't turn on unless AC is running

So first of all, I've changed nothing: same thermostat and same everything. I typically run my blower fan 24/7, but a few days ago it stopped working unless the AC is on. Which tells me that the ...

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