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

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2
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1answer
1k views

Is it normal for A/C performance to improve when vent covers are removed?

I recently moved my office to the second floor of our home and I haven't been able to get the temperature below about 78 even though the thermostat is on 72. My son's bedroom had been the same way ...
2
votes
2answers
793 views

Recommended proximity of HVAC vent to return air

I have an upstairs room with an HVAC vent in the ceiling above the door. The return air is in the hallway just outside of the same door. This room also happens to be the hottest room in the house (by ...
0
votes
2answers
247 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 ...
0
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2answers
319 views

Why doesn't my gas furnace ignite?

I had a Lennox slp98dfv installed last year - it has a surelight ignition - it now just blows cold air - so I assume the pilot light is out - but not sure how to light it - as u cannot manually ignite ...
2
votes
2answers
122 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 ...
0
votes
1answer
249 views

Can I use a heat gun to melt the Ice from the external part of split ductless system?

I've got a Mitsubishi Mr. Slim split ductless system in the "mother-in-law" suite of my house. There are 3 wall units connected to it, one in the front room, one in the bedroom, and one in the ...
2
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3answers
1k 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)?
0
votes
1answer
105 views

Is it OK that my AC is making squeaking and rattling noises?

Just want to get some initial thoughts before the repairman comes. I have a 3 year old 2.5 ton Goodman AC unit. I set the temperature to 74°F last night (AC) and woke up to a nice and chilly ...
34
votes
4answers
122k views

How can I add a “C” wire to my thermostat?

So, the spiffy new wi-fi thermostats want power on the C wire from thermostat, but the old thermostat doesn't have a C wire at it. What's the easiest way to add the C wire/24 volt to the thermostat ...
0
votes
1answer
76 views

I have both a natural gas burner with baseboard heat and 6 Mitsubishi Mr. Slim units. Which would be less expensive to use for heating my house?

I just purchased my house a few months ago. The house has both a 2 zone natural gas burner with baseboards for heat and 6 Mitsubishi Mr. Slim units that I can use for either A/C or heat. I am not sure ...
1
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1answer
1k views

Why is my furnace blowing hot air outside through a PVC pipe?

I turned on my furnace and went outside and noticed hot air blowing out a J-shaped PVC pipe. Is it a vent or error that needs to be plugged?
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0answers
133 views

How do i connect the common c wire in a carrier air handler?

I need help in determining where to hook up the common c wire for my new thermostat. The carrier air handler appears to be a little more complicated than others.
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0answers
90 views

Spiral pipe size vs. CFM for AC

My AC contractor just brought some 8 and some 6 inch spiral pipe to install tomorrow. I do not trust him nor do I trust a single contractor out there, hence posting here to confirm. I am getting a 3 ...
0
votes
1answer
65 views

How can we protect this furnace from environmental conditions?

I was recently asked to look over the utility closet of a friend, and several things I saw looked very concerning, from an energy-efficiency standpoint. This closet is approximate 3' x 6', and is in ...
1
vote
1answer
34 views

Testing AC ductwork

I am about to bring in a contractor to install central AC in my house. I am in the final stage of a rather comprehensive remodeling effort, all of which was done either by me directly (cca. 85%) or ...
3
votes
4answers
3k views

Why would a furnace overheat with a standard density filter?

Some time ago I found my furnace (gas, forced air, downdraft) was getting stuck on, blowing cold air. I could reset it, but it would happen again after a while. After calling out a service man, I ...
0
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1answer
112 views

Legal requirements regarding 100% asbestos duct work [closed]

I am renting a condo. After starting the heater, dusty air came out of the registers, so I called out a company to clean the ducts. They verified the ducts are 100% asbestos and cannot be cleaned. ...
1
vote
1answer
641 views

Is it okay to connect a round supply duct directly to an air handler?

I removed all of my existing duct work that was designed as a radial system with a sheet metal rectangular plenum with very long flex runs poorly attached. I am replacing my system with all round ...
0
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0answers
139 views

Is it possible to insulate existing ducts without removing drywall?

My second story is always warmer in the summer and cooler in the winter than the ground floor. I've had the ducts cleaned and sealed and I've also adjusted the blower motor speed. It occurs to me that ...
0
votes
2answers
4k views

What size breaker and wire do I need for central air conditioning?

I am getting ready to hang drywall in my basement but before I do that, I need to run wire from the main panel upstairs to the future location of the central AC furnace through the basement ceiling ...
3
votes
2answers
545 views

Can I attach a HEPA filter to the HVAC outlet?

I am currently living in China and want to improve the indoor air-quality. We have a Hitachi R410A HVAC. All the room in the house are controlled separately. Just to make it clear up front, I am not a ...
1
vote
1answer
593 views

How to diagnose a broken Aprilaire humidifier (Model 600)?

I have an Aprilaire Humidifier Model 600 (or maybe 600M) mounted on my furnace. The humidifier is not turning on (i.e. letting water flow over the filter) when the furnace is on. The below images ...
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vote
2answers
198 views

How do I close this hole in the HVAC vent?

What's the best way to close up this hole in the venting leaving the hvac? Would foil tape be sufficient? Right now it bleeds out hot air into the basement in the winter, and cold air in the summer. ...
2
votes
1answer
673 views

What can I use to adequately insulate round rigid metal ducts?

I'm installing properly sealed round metal ducts in my unconditioned attic for heating and cooling. I've probably got 100' total of 6" duct to cover. I'm trying to achieve an R-8 insulation value, ...
1
vote
0answers
543 views

How can I tell if my bathroom ceiling vent is working properly?

Seems to take the vent forever to clear shower vapor from room. I purchased a vent that had a good rating. It is vented to the outside. How do I know if it is working properly and actually venting to ...
1
vote
4answers
867 views

Are 5" thick filters for furnace/Central AC still available?

My furnace/AC was installed about three years ago. It uses 16" X 25" X 5" filters. The problem is when I try to find a replacement at my local home center: at Lowe's, Home Depot, (you name it), I ...
4
votes
3answers
2k views

Why is my gas furnace vibrating when blowing hot air but not when blowing cold air?

I have a gas furnace. I recently replaced a bad blower motor. At that time I also cleaned out the blower housing and squirrel cage. The AC runs fine with no vibrations or any symptoms of an off ...
4
votes
1answer
2k views

Is flexible gas pipe safe to use for main or long runs?

The house we purchased is a "tear-down". A builder bought the older structure, partially tore it down and built a bigger house on the old footprint. A lot of the original gas piping is still in the ...
2
votes
2answers
384 views

Can an 18 inch duct be replaced by 4 smaller ducts?

We have a return air duct that is 18 inches in diameter that had to be soffited. Not a big deal except it is taking up closet space in what is otherwise a very small closet for a kids bedroom. Can ...
0
votes
1answer
2k views

How do I add a C/ Common wire to my “Specific” HVAC system? [duplicate]

I just bought a new WiFi thermostat that requires me to add a C-Wire at the furnace. I have read the questions related to my issue but would like a suggestion on my particular (incredibly OLD) ...
0
votes
1answer
304 views

How do I maintain an 80% efficient natural gas furnace?

I have an 80% efficient gas furnace at my house, that is seemingly working well and is configured with an air conditioner. What preventative maintenance should be done to it, and at what interval? Is ...
0
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1answer
442 views

Can I cover a high efficiency HVAC vent?

Just moved into a house with a High efficiency HVAC (heating and air conditioning) which vents to the outside ( with a booster fan). the outside pvc pipe is just " open" . no cap, no screen.. i know ...
1
vote
1answer
362 views

How can I prevent the fireplace smell when the A/C is on?

I get the ashy fireplace smell in the family room when the A/C is running. I haven't had a fire burning in months. I checked out this question, but it targets a recent fire and a cold air return. ...
0
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0answers
98 views

AC won't turn on after replacing thermostat batteries

we replaced the batteries on our thermostat after they began flashing for a few minutes. We'd been using the heater up to that point. After replacing the batteries, the heater does not turn on ...
0
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0answers
52 views

Mold in the air conditioner “pantry”

Maybe four years ago, our AC "froze up" (as I recall), and there was water soaking into the wood it sits on. (The inside unit is in a hall closet with the big air return vent underneath it.) Later I ...
0
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1answer
97 views

Why does my HVAC begin vibrating and stop cooling at night?

I am calling a HVAC technician since this is probably too complex a problem for me, but wanted to hear some possible diagnosis. The symptoms are as follows: The A/C is working well during the day ...
2
votes
1answer
73 views

How do I determine how efficient my furnace, A/C, and windows are?

I just bought an older home. The furnace, A/C, and windows are functional, but I suspect there may be some efficiency gains to be made. Is there any way to determine/estimate how efficient those are ...
1
vote
0answers
515 views

Reducing air conditioner compressor vibration noise

I have a two year old Carrier air conditioner with an outdoor condenser. The condenser sits on a plastic pad on the side of my house, and I have two--one for downstairs and one for upstairs. ...
1
vote
0answers
1k views

How do I size a wall sleeve for a through-the-wall air conditioner?

We are shopping for a through-the-wall air conditioner. We do not currently have a hole in the wall with a sleeve in it. We are trying to figure out what sleeve to buy. The air conditioner we like ...
4
votes
2answers
813 views

What is the maximum angle I can set my window AC unit?

We know an AC unit must be angled to allow runoff. But what is the maximum angle and what is the issue with having to large of an angle? I've seen people say the angle is "5/16" or "3/16" but this is ...
2
votes
1answer
1k views

What could cause a replacement A/C condenser fan motor to only run for 3 minutes?

Just replaced a GE 5KCP39FG Condenser fan motor with an AC Smith FSE1026SF. HVAC Counter sales told me it was the right one and gave me a Partners Choice Capacitor 01-0085 to match. Old motor 3 ...
1
vote
1answer
119 views

Is it possible to detect and repair a refrigerant leak in my HVAC system?

While replacing the blower motor in my HVAC's air handler, the technician mentioned that the refrigerant in the system was also low and that most likely there was a leak. Is the leak something that a ...
2
votes
1answer
3k views

How can I add a “C” common wire to this system? [duplicate]

I would like to add a "C" / Common wire hookup to my hvac system and get a fancy new thermostat. I've read Options for adding "C" wire to thermostat and still have some questions. First of ...
1
vote
1answer
178 views

Can I connect two separate ducts systems together?

My apartment, which I own, is split upstairs by two hallways. Each hallway has its own A/C unit, to cool 6 single person rooms each. Recently the south side A/C broke. I have called the repairmen out ...
2
votes
1answer
447 views

Replace 7“ metal duct with 6” flexible or 8" flexible?

I am replacing the flexible ductwork in my attic, which is a mix of ancient 6" and 7" metal ducting. I'm having a hard time finding 7" flexible ductwork for sale locally, but no problem with 6" and ...
3
votes
1answer
2k views

Where should I tap in to the existing duct work?

Bought a 1981 repo a year ago. The house measures around 900 SQFT. I enclosed the one car garage (10'x20') @ 200 SQFT to serve as an office. The front of the garage is insulated (10') along with the ...
3
votes
1answer
148 views

Should I use a quick or gradual 90 in my flexible A/C ductwork?

To elaborate a bit more. If you are running an 8" duct off the supply, would you do a quick 90 degree towards the destination or do a gradual 90 degree? I would guess a quick would be better because ...
3
votes
1answer
5k views

How should I wire this White-Rodgers fan and limit control? What about the thermostat?

I have a wood-burning stove, that is used as an auxiliary heat source in the house. There's a regular electric furnace, and adjacent to it is the stove. The warm air duct (out) from the stove ...
1
vote
2answers
339 views

How can I locate a short in a 24V central A/C circuit?

My A/C is not working. I checked the panel and the LED light code told me that there was a fuse blown or a short in the circuit. I checked and confirmed that the fuse had blown. If the fuse blows ...
4
votes
3answers
854 views

Advice for replacement/repair of an HVAC with a cracked heat exchanger?

My townhouse has a downflow 1994 Rheem 2.5 ton HVAC unit on its roof (combines both A/C and heat). We have had two issues with the unit and have been in the townhouse for a little under two years. In ...