(Heating, Ventilating, and Air Conditioning) For questions about installing, repairing, and troubleshooting HVAC systems.

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1answer
67 views

Did I wire this thermostat properly?

Just want to make sure I have this correct: Have M1MB 070a BW heat/ac unit w/ a 710152B control board and a Coleman outside condensing unit. -Have a four wire thermostat. R,Y,G,W -Have 2 wires coming ...
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1answer
77 views

Will splitting a duct to extend HVAC to an addition cause problems?

I'm building a 15 x 26 addition off of current family room to use as a music room. The family room has 2 vents(registers) where the family room meets the new room, and because of convenience they ...
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1answer
115 views

Does anyone have experience with small heat-recovery air exchangers?

I know there are units made which are supposed to be sized for use in a residential kitchen, as a more efficient replacement for the usual vent hood (bring air in to replace air blown out, but ...
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1answer
192 views

Why does the blower in the attic vibrate during heating when it is really cold?

We have a Carrier heat pump system in our home, and the blower is located in the attic. When it is especially cold, the blower runs on high (there are three levels: high, medium, low). During this ...
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1answer
185 views

Can I remove my vent covers without disconnecting the duct?

I have an old house with flexible duct work in the ceiling. There is mold in at least one. Can I remove the vent covers to clean or will that disconnect the duct work in the attic from the vent ...
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1answer
70 views

Can you vent electric dryer into furnace return?

I've got an electric dryer currently vented outside: Behind the door to the right is our heat pump furnace: I was thinking about, during the winter, venting the dryer (properly filtered for lint) ...
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0answers
12 views

What could cause my Trane furnace to not light?

after I set my thermostat for heat the combustion fan motor comes on but the burners does not fire, and after like two minutes everything turns off and the LED flashes two times, which means SYSTEM ...
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0answers
30 views

Furnace blower intermittently stops working

The blower on my furnace is set to be on constantly. The last two nights in a row I have woken up in the middle of the night to hear that the blower is not running and that the temperature is dropping ...
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1answer
203 views

Why does my heat pump keep triggering the high-pressure cut-off?

Our Rheem heat-pump is on the fritz. It keeps triggering the high-pressure cut-off on the outdoor unit. We've had problems with this happening before, but only when the outside temperature got to ...
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1answer
75 views

Why would only 1/3 of my registers be blowing warm air?

I have a Coleman gas furnace in a wall space in my house which somehow shares the blower on my a/c unit on the roof because it turns on when furnace is called to start, though it does bump up after a ...
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1answer
462 views

Where is my common wire on the unit?

I have 2 systems in my house, my heat is gas hot water radiator heating and A/C is a separate newer system. I'm trying to figure out if I can run a C wire off air handler from the A/C system to run ...
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4answers
4k views

Are there efficient ways to provide combustion air to heating appliances?

In a previous question we established that there probably should be a vent between my utility room (which opens into the kitchen and living space in general) and the outdoors (in my case the attic, ...
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4answers
10k 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 ...
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5answers
8k views

Can I modify the vent from my high efficiency furnace to prevent possible damage to the exterior of my home?

is my high efficiency furnace vent installed properly? I'm based in Toronto, Canada. In some recent cold winter weather, the exhaust is causing a lot of ice buildup on the surrounding brick. To my ...
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2answers
4k views

AC Unit Blow Warm Air Indoor But Colder Air Outdoor

I have two AC Units. One for upstairs and one for downstairs. The upstairs one works just fine but not the downstairs. So, i did a test by turning both units on and went outside to compare the two ...
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0answers
17 views

baseboard heat problems it makes loud noises and does not heat 2 zones at the same time

The baseboard heat will heat the main floor and not the upstairs and vice a versa. What could be the problem, it also makes loud noises.
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1answer
217 views

What does the low limit do, and where should it be set on an oil fired hot water furnace?

What does the low limit do, and where should it be set? My furnace has a honeywell triple aquastat relay and has a difference dial. Water temp is about 190 deg F. Also, water psi gauge is only ...
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2answers
66 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 ...
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0answers
42 views

Why won't my thermostat control the HVAC anymore after trying to switch thermostats?

I bought a new Nest thermostat which is supposed to be compatible but needs a professional installation (advice that should have been heeded by non-professional electrician me). This is to replace an ...
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2answers
52 views

Is there any risk of running both the fan and furnace at the same time?

I am attempting to build my own thermostat using an arduino and a few relays and have been trying to map the appropriate wires so I don't damage my furnace/AC unit. This is a picture of my ...
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2answers
57 views

How do I calculate how long a furnace has to work to compensate a given temp drop?

I am trying to understand the dynamics of heating a home after the furnace size was calculated. Say you have a 60000BTU furnace to heat a 2000 sqft home. At the beginning of the heating season you ...
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1answer
57 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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0answers
30 views

Does polarity matter when wiring a humidifier solenoid?

The 56 was receiving 24vac whenever the furnace was on via a red wire and a white wire. 24vac was supplied to the solenoid when humidity was called for via a pair of junction terminals. The 4655 is a ...
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1answer
125 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
42 views

Adding a “C” wire for a wireless theromstat [duplicate]

I have a heat only system with two wires leading to the thermostat - red and white - and am wanting to add a wireless thermostat. The new thermostat however requires a "C" wire. Can I add a C wire?
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1answer
51 views

How can I remove ductwork that is butted against a foundation wall?

I need to remove the existing ductwork in my basement to install insulation behind it. I'd like to do it without destroying the ductwork. The vertical duct is right against the foundation, so I can't ...
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0answers
46 views

Is it normal for this PVC pipe to be dripping from under the eaves?

I have a 2 story house, 14 yrs old. There is a PVC pipe under the eaves over a window on the 2nd story, that has been dripping more than normal the past couple of days. Our AC unit is located in the ...
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0answers
18 views

What type of control systems are available for a home with multiple HVAC systems?

Our new (used) home has two HVAC systems, one for upstairs and one for down. There is a thermostat in the dining room, which is directly affected by sun. And one in our bedroom, that clicks all ...
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1answer
40 views

Why won't my electric furnace kick on unless the thermostat is set to 73?

I have an older, ill insulated mobile home. My house is obviously not 73 degrees, and my heater will not kick on. I set it to 73 and it finally came on, but then the furnace would not shut off. It ...
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1answer
232 views

How do I connect a C wire to an Utica PEG112CDE steam boiler?

I want to upgrade my old mercury thermostat that I currently have to a newer programmable thermostat. This little DIY project is for my first late 1920's home that I recently purchased. I currently ...
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2answers
1k views

How do I disable a thermostat to prevent it from turning on the AC?

I need to disable my thermostat from turning on the AC. Yes, covertly. I think one of my housemates is missing his native Antarctica. So, the thermostat still must be active & setable, but I want ...
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1answer
22 views

What would cauase a limit go bad in a furnace?

On Christmas day my furnace pilot would not kick on and the blower just kept running on and on blowing out cold air. A furnace tech came out and looked at it. He said the Limit was bad and he replaced ...
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5answers
8k views

What kind of wall switch is needed for a natural gas fireplace to ignite consistently?

When we moved in, our natural gas fireplace worked well: Flick the switch & it would ignite. Years later, it started acting erratically: Sometimes, the switch worked, other times, no luck. We'd ...
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1answer
89 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
39 views

When to Replace UV Bulb in AC System?

We had a new AC system put in last summer. The contractor included a UV bulb between the cooling area and the supply fan. It's supposed to kill bacteria and other nasties in the air. (The bulb is ...
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2answers
723 views

HVAC air handler with a built-in humidifier

I am in the process of choosing an air handler to use only for AC. I plan to keep radiant heat. However, in the winter, I would like to use the AC system to blow humidified air to compensate for the ...
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0answers
31 views

Should I look into getting an active or passive whole-house humidifier?

My wife and I moved into our place a few months ago. Now that is is winter, the humidity levels dropped down to 20% throughout the house. We want to install a whole-house humidifier to raise it up ...
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3answers
217 views

How to measure air flow coming out of registers?

As my contractors finish installing ductwork and the air handler for my central AC system, I would like to have a measure of how many CFMs come out of each register, as a function of how the system is ...
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0answers
23 views

How to clean carbon build-up on Honeywell whole house air purifier made of aluminum?

Bought a house recently that has a Honeywell F300 whole electric house air purifier/cleaner. The cell's aluminum fins have a black baked-on dust that I expect is preventing the unit from working as ...
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2answers
4k views

How do I connect the common wire in a Carrier air handler?

I am trying to install a new wifi thermostat in my home and need to locate the common terminal for my air handler. I have a Carrier model FB4CNF030. It's a new construction home and I have the blue ...
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0answers
10 views

old furnace and thermostat upgrade

In a furnace that has no circuit board, can the C wire be connected between the C terminal on the thermostat and to one of the contact leads on the 24V transformer and operate safely?
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1answer
67 views

The hot water is working but the radiators will not heat up!

We have a Utica Boiler model number SFH4150WT and we are receiving hot water but the radiators do not heat up!!. We tried bleeding the radiators, they only heated up a little bit but after about 5 min ...
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1answer
97 views

What could cause a condensing units fan to stop working?

My AC unit fan stopped working suddenly. I tested the 3 pole condenser (capacitor) and the it looks OK ( 45 uf , 5 uf is what is mentioned in the spec of capacitor). I tested the resistance in the the ...
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2answers
51 views

How do I find air vents that are covered over with popcorn ceiling?

My house has several areas where we are have no heat vents and these areas are quite cold. Others areas have vents even in the closet spaces. I found one covered vent after walking through my ...
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3answers
6k views

Ethernet cable instead of Thermostat wire?

I need to pull new wire from my furnace to my thermostat and was wondering if there would be any problems in using an Ethernet cable instead of standard thermostat wiring. The reason being is I have ...
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3answers
4k views

Does a whole house humidifier go on the intake or outlet of the furnace?

On what side of the furnace do I install the tank of the humidifier (the warm side or the return air side)?
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0answers
38 views

Testing the exhaust of a natural gas furnace?

I recently had maintenance performed on my natural gas forced-air furnace. During this maintenance, the technician went outside and used an electronic handheld device with a wire-attached probe to ...
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1answer
39 views

Could an unlevel furnace be causing noise from the blower fan?

The blower fan on my gas furnace sounds like it is hitting other metal when it turns on or off. I had it serviced and he replaced the blower run cap but it has started again after about a week. ...
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2answers
123 views

Should I patch this hole in my slab?

I'm in the process of tearing out carpet and installing laminate in my guest bedroom. After I got the carpet out, I discovered a hole several inches across underneath the wall that borders the garage. ...
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4answers
5k views

How can I use a separate transformer to provide a C wire to my thermostat?

I Purchased the Honeywell WiFi Prog Thermostat to replace my Round Digital Honeywell Thermostat. I have separate Heating and Cooling (Heating is a Weil McLain Boiler for Hot water baseboard and Hot ...