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

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3
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1answer
3k 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
70 views

Is it ok to stand atop my central A/C unit to install a missing soffit vent?

Unless I go on top of the roof, it's the only to get to it without a step ladder. I don't know if the covers on these things are meant to stand the weight of a 250lb guy. Aside from falling and ...
3
votes
1answer
296 views

Is it normal for air to be leaking from where the drain hose connects to the central A/C unit?

I'm trying to determine if I have a leak around my central AC unit. Basically when the unit is on, I feel cool air blowing outside the "furnace plenum" as I believe its called. If you look at this ...
3
votes
1answer
56 views

Is there a wireless way to cut off the HVAC y wire from my generator transfer switch?

I recently had a Generac Synergy generator installed, which went smoothly, however there was no good way to get the Y wire from my thermostat to the transfer switch and back in order to allow the ...
3
votes
0answers
77 views

Adding vents to duct?

My house has forced air HVAC. When I finished the basement, I used a closed cell foam insulation that worked very well. The basement will get only 8 degrees cooler than the first floor during a time ...
3
votes
1answer
57 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 ...
2
votes
3answers
1k views

How can I repair these rusty electrical connections?

When I turn on my air conditioner at the thermostat the vents kick on but nothing outside. Also the last time that it worked it took a few minutes to get going and was pretty loud. I checked the ...
2
votes
1answer
117 views

What is the cost of one percent efficiency on an oil heater?

We've now had about 7 contractors come to our house and give us estimates for replacing a) our oil heater (system from the early 1980's, estimated at around 65% effeciency), and b) our central air ...
2
votes
1answer
132 views

Help me choose AC model

I need air conditioning (no heat; I've got hot water radiators) for the main floor of my house (around 1000 ft2). I was offered the following models (mostly Carrier) (ordered by price, descending): ...
2
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3answers
5k 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)?
2
votes
2answers
399 views

How much current should I expect this motor to draw when it's running steadily?

This fan lists its "Max. Amperage" as 3.2. I assume the motor draws that much when it's first turning on, then settles down to some lower current. How much current should I expect it to draw when ...
2
votes
2answers
564 views

At what temperature should an unoccupied house be kept at in winter?

We are moving to a new house and unfortunately we don't have our house sold yet. I was wanting a recommendation as to what temperature to keep the furnace going @. I found a good recommendation to ...
2
votes
2answers
2k 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
1k views

What is going on with my central air?

I have a re-occurring issue with my central air. I have changed filters, cleaned all three intake vents and even had a serviceman out on three different occasions (two separate companies). My problem ...
2
votes
1answer
265 views

Will an electronic air filter harm my furnace?

If I install a furnace-mounted, electronic air filter, like this one, will it harm my furnace due to reduced air flow? How will I know if it reduces air flow too much?
2
votes
2answers
976 views

How do I lower a cold air return from the ceiling for a basement rental?

I am living in the basement level of a rental unit with forced air heat. There are 9 heating vents and one cold air return, all of which are in the ceiling. The air isn't mixing very well resulting ...
2
votes
1answer
4k views

Air deflectors on floor registers and cooling efficiency

I was once told by an HVAC technician to avoid using air deflectors on floor registers during the summer. The reason was that the last thing you want to do is to direct the heavier, colder air ...
2
votes
1answer
57 views

Should I be worried if my A/C ran with the cover on?

My wife accidentally switched on the "cool " mode and the a/c was activated, however the cover was still on the unit outside. Ran like this for about 2 hours. I noticed it and turned it off and went ...
2
votes
1answer
344 views

Breaker box or heat pump problem?

We ran our forced air heat pump today. 15 min. in we noticed it just stopped running. Looking in the breaker panel I could see that the breaker for the heating unit had tripped. When I tried to ...
2
votes
2answers
1k views

Furnace flashing 4 times (Ducane)

My Ducane furnace flashes 4 times, runs for 5 minutes, and then the burner goes off. When the limit switch is jumped it runs good. What needs to be changed here?
2
votes
3answers
262 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 ...
2
votes
2answers
155 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 ...
2
votes
1answer
2k views

Why isn't my heat pump system kicking out cool air this year?

I have a Carrier heat pump/air handler system (looks pretty old) with a honeywell T-stat (looks pretty new) and I am not getting cool air. Heat worked all winter, but I have used it in at least a ...
2
votes
1answer
521 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 ...
2
votes
2answers
972 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 ...
2
votes
1answer
4k views

Why is there water dripping from my ceiling AC vents?

I have a one story house with hot water heat. The house also has forced air AC ducts running from the attached garage, in the attic, down into the living room, bedrooms, and kitchen. At certain times ...
2
votes
2answers
1k views

How do I clean an AC condensate pan?

I have a Ducane HVAC system that started leaking out of the evaporator coil housing. Mine looks like the EU1P. I read that i need to clean out the drip pan. II tried cleaning it by sucking out the ...
2
votes
2answers
99 views

Should I convert from a rooftop to a split HVAC system?

We have a packaged HVAC on the roof and the AC needs to be replaced. It's 23 years old and dying/dead. We were considering buying just an AC and keeping the package unit running for heat. We feel ...
2
votes
3answers
714 views

Can I cap the air return in my unfinished basement?

I noticed today that there is a massive air return in my unfinished basement. The opening is about 2 meters from the blower, and as large in diameter as the return duct coming from the upstairs. This ...
2
votes
2answers
323 views

How can I prevent my clothes dryer door from fogging up?

When I turn the air conditioning on in my house, the inside of the window in the clothes dryer door fogs up. Also, if clothes are left in the dryer, they become slightly damp again. How can I prevent ...
2
votes
5answers
13k views

What could be causing an A/C blower motor to turn off randomly?

The Blower motor on my AC unit turns off at random times while the outside unit continues to run which is causing the coil to freeze up. The blower won't come on for 30-45 minutes after the AC has ...
2
votes
1answer
2k 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 ...
2
votes
3answers
3k views

How can I improve hvac air flow to my attic?

Two years ago I converted the attic of my 1.5 story house into a livable space. It had no HVAC ducts going up, so I ran some coming from the basement where the furnace is. Air flow to the attic via ...
2
votes
1answer
2k views

Does an air return duct do anything when the air conditioning or furnace is not running?

I recently had a contractor create a new wall which cut me off from the rest of the house. There is one AC/Heating vent in the room and when the door is closed it gets very, very hot. As soon as the ...
2
votes
1answer
144 views

When I set the thermostat to X degrees, is that the temperature at which air is pushed out through the vents?

My hunch is that most ac units aren't that sophisticated, and they just pump air that is "cold enough" or "hot enough" and pump it until temperature rises to the specified value. Is that right?
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 ...
2
votes
2answers
342 views

Air conditioner not blowing cold air

My HVAC system had a problem during the winter where the blower motor stopped working. I got a HVAC tech to come out and replace it. However, now that it's hot again, the cooling system is still ...
2
votes
2answers
52 views

Are there optimal positions for A/C and heat register grills to be facing?

I noticed a while ago that some of my A/C and heat register grills are facing the walls and not the room (the insides of the curves on the grills face the walls) in some rooms but not in others. My ...
2
votes
2answers
99 views

How should I wire a Trane air handler & heat strips?

Looking for validation or correction on my understanding of requirements for wiring 5 ton Trane air handler with 20kw heat strips. Of course, I read the label and identified that there are (2) 240v ...
2
votes
1answer
123 views

Is it possible to add a “C” wire to my electric heater?

I bought a Wifi Thermostat but my old thermostat did not have a Common Wire. I can't use any of the swapping the G for the C solutions because I have an electric heater. I was told by Honeywell that I ...
2
votes
1answer
96 views

Is there a reason for an exterior vent not connected to anything?

I have an exterior vent on the side of my house not connected to any piping within. You can look inside and see wood/concrete/insulation into the cavity between the basement ceiling and main floor. ...
2
votes
2answers
888 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 ...
2
votes
1answer
79 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 ...
2
votes
2answers
2k 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 ...
2
votes
1answer
1k views

Should I install a damper above my return air duct for better upstairs cooling?

I have a finished basement, ground floor, and upstairs. The ground floor and basement cool nicely with the AC. The upstairs doesn't cool very well. The returns are really just holes in the drywall- ...
2
votes
1answer
326 views

Why do they put an A/C vent in the utility room?

A related question is here about a year ago: Is there any reason to not tape this vent over? My question is, why do they put the vent there in the first place. Like the previous poster, I just bought ...
2
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2answers
2k views

What type of air conditioner can bring in outside air?

Car air conditioners usually have the option to choose circulate on/off. What about house air conditioners? For instance, does a window air conditioner exchange air inside and outside the house?
2
votes
1answer
343 views

What is a quieter alternative to gas forced air heating?

My small 1BR apartment has an old gas furnace that works great, but costs my landlord too much to insure. He plans to install gas forced air, an in-unit upright furnace. I'd love to suggest a ...
2
votes
3answers
8k views

Are there any ductless mini split systems that offer standard HVAC wiring controls?

Have been looking for in the US a ductless mini split heat pump system something like the Mitsubishi Electric Mr. Slim that uses a non proprietary wiring scheme for its wall mounted thermostats. ...
2
votes
1answer
416 views

What is involved in sizing and designing ducts and ductwork?

I have a one-story house, and it looks like it would be easy to run new ducts myself in the attic. What should I know before trying to design a duct system myself? I have seen ductwork that's metal ...