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

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2
votes
1answer
2k 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 ...
3
votes
2answers
1k 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
1k 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 ...
0
votes
1answer
933 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 ...
0
votes
1answer
477 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 ...
0
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1answer
165 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
vote
1answer
8k 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?
0
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1answer
80 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
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1answer
41 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
7k 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
166 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
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1answer
2k 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
346 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
30k 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 ...
1
vote
2answers
395 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
3k 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
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0answers
1k 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
2k 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
1answer
7k 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
1k 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
3k 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
698 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
votes
1answer
1k 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
1k 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. ...
2
votes
1answer
86 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
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0answers
1k 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
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0answers
3k 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 ...
2
votes
1answer
3k 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
188 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
5k 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
466 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
590 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
5k 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
274 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 ...
4
votes
1answer
10k 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
2k 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
2k 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 ...
18
votes
3answers
11k views

Is running ethernet cable through an air return allowed under US code?

I'm looking to wire up the second floor of my house and the cold air return provides a convenient, straight run from the office to the utility room. Is it safe and within code to run ethernet cable in ...
2
votes
2answers
4k views

What does this square icon mean on my Honeywell thermostat?

I have upstairs Honeywell Thermostat showing me a square icon since yesterday. The upstairs AC is not working. It is blowing air since the fan is on but the air is not cold. I opened up the ...
2
votes
2answers
3k views

Can I remove the fresh air supply that is attached next to my furnace?

It looks like my gas furnace is already vented but I'm not sure. There are two white pipes from the top of the furnace that are vented outside. The furnace is a Trane XR90. We have cold winter climate ...
1
vote
1answer
3k views

How to efficiently circulate air to keep room cool?

I live in Indonesia and I have an apartment with a 6.7 x 5m room, which contains a dining table and a couch. In this room are two 1.5PK (13,000 BTU) AC units on the same side of room nearer to the ...
12
votes
3answers
3k views

Would providing shade for my air conditioner's condensor improve its efficiency?

Our house has two A/C systems; one for the bedroom level, one for the remainder of the house. The compressor/consdensor units are outside the south side of the house, and in direct sun all day, now ...
0
votes
0answers
35 views

How can I determine if a valve complies to MSS?

How to know if the valve complies to Manufacturers Standardization Society (MSS) or not? I want to approve a valve for an HVAC project, but I don't know how.
1
vote
1answer
295 views

Replacing Oil Furnace with Heat Pump

My wife and I would like to remove the older oil heat from our home and replace it with a heat pump. We currently have an Amana central air conditioning unit (3 ton), and an oil furnace in the ...
0
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1answer
200 views

Why is my AC blowing from this pipe and freezing up periodically?

I looked under my mobile home and found a hose coming from the flooring. It is blowing cold air out, and it also looks like water has been dripping out. I think that this is normal, but why is all ...
7
votes
1answer
988 views

Why did an HVAC installer add this PVC pipe?

We recently had a VERY old central heating furnace replaced and I noticed that the HVAC installer added the following PVC pipe shortly before the inspector arrived: The metal vents were already ...
5
votes
3answers
97 views

How to find areas where heat/coolness are lost?

I live in a 2-story rental townhome (basically an apartment with 2 stories). Our central air/heat system isn't really the best at keeping the upstairs and downstairs the same temperature whether in ...
0
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0answers
34 views

Is my heat pump's condenser fan motor bad? [duplicate]

The other day my AC stopped working. I'm thinking the condenser fan motor has gone bad (unit is ~10 years old). Here is what I did to troubleshoot which led me to believe it was the fan motor. ...
2
votes
2answers
263 views

Why is my AC suddenly *heating* my house?

I have a 13 SEER heat pump about one year old. Everything's been working fine, but the AC suddenly started heating my house spontaneously (no changes to thermostat, etc). The outside ambient ...
1
vote
2answers
5k views

Which terminal should I connect it to for a “C” wire when none are labeled “C”? [duplicate]

I am looking to replace my old battery operated thermostat with a new wifi model. There is no "C" common wire connected to my old thermostat. There is a blue wire that is at the thermostat but cut ...