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

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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
3k 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
146 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
373 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
71 views

Do I need an HVAC vent in this bathroom?

The finished portion of my basement was completed after the original construction. I've found a few questionable practices, including the lack of an HVAC vent in the basement bathroom (shown in green ...
2
votes
1answer
56 views

How can I increase the effectiveness of the A/C in a hot 2nd floor converted attic master suite?

Just bought a 1940's masonry construction house. House has a finished basement (cold as a meat locker), first floor (comfortable) and 2nd floor (too hot). The 2nd floor is an attic that has been ...
2
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1answer
122 views

central a/c won't cool

My A/C unit was just checked last week- the tech said it had enough freon. Monday we had a nasty storm- electricity flickered, but never went out. After the storm, we noticed the a/c went on, but it ...
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2answers
268 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 ...
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2answers
32 views

Can I use a secondary thermostat as a timer for my air conditioning system?

I want to install a timer on a split air conditioning unit to accommodate my energy plan hours. Too many people change the thermostat. Could another thermostat be used at the pump, controlling one ...
2
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2answers
347 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
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1answer
188 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
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1answer
83 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
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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
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1answer
2k 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
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1answer
393 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
3k 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
380 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
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3answers
11k 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
444 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 ...
2
votes
1answer
1k views

Why would a repairman install a 1/3 HP fan motor into a 1/5 HP unit? [closed]

Why would a repairman install a 1/3 HP fan motor into a 1/5 HP unit? He had to cut the shaft to make it fit. Two weeks later unit quit again and then he had to come and replace the capacitor MFD ...
2
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4answers
3k views

How “freely” should a central A/C condenser fan spin

Last year my home's central air condenser fan motor stopped working. When I noticed the house wasn't cooling down I went outside to investigate and found there was a humming sound coming from the ...
2
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1answer
487 views

Will I see any performance gains if I reconfigure my thermostat to control the second stage of my 2 stage furnace?

Our furnace is a two stage one that was installed last year (a Bryant 80t). When it was installed, it was installed with a thermostat for a one stage furnace. This appears to be because this model ...
2
votes
1answer
2k views

How can I prevent heat loss through heater/air conditioner wall units?

HVAC experts out there... I live in Wisconsin and it gets mighty cold here! I have a condo with 2 wall units that are used for both air conditioning and heat. My heat bill in the cold winter months ...
2
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2answers
4k views

How can I tell what kind of heating system I have?

Seems like a simple question, but I've had a very hard time finding a definitive answer to this. I went to the hardware store to buy a replacement for a faulty thermostat and when I arrived and ...
2
votes
1answer
3k views

How do I fix a condensate drain line that froze in my split electric system with heat pump?

I have a split electric system with a heat pump. It looks like my condensate drain line is frozen. I switched to supplemental heat which does not use the heat pump. Is this enough for now? Our ...
2
votes
1answer
110 views

What is the best place to install an Air-conditioner in a room?

I'm trying to decide where to install my ductless split Air-Conditioner. For the indoor unit, is it ok to install it above a window? will placing the indoor unit at the corner of the wall reduce the ...
2
votes
1answer
701 views

AC unit won't turn on: both inside blower fan and outside fan unit won't turn on

AC unit won't turn on: both inside blower fan and outside fan unit won't turn on. It is as if I had gone to the circuit breaker and cut the power to the whole HVAC system, but I didn't. I've been ...
2
votes
2answers
63 views

How can I add a C wire with this unusual installation?

I recently got a new Honeywell WiFi thermostat, which requires a C-wire. I have 5-wires going to my current thermostat, with only 4 being used. So I thought adding the 5th as my C-wire was going to ...
2
votes
1answer
66 views

Can I use a power gable fan and ceiling louver vents to pull cool air into my house?

I live in L.A. We only have really hot weather 5-10 days a year and it usually cools off at night (outside). I also have a large Gable vent in my attic. (recently added with addition) I would like ...
2
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2answers
72 views

Can I replace a high limit switch myself?

Thank you for the answer, can I change this myself or do I need to get the HVAC company to do this? I have turned off the breaker in the panel box so that it does not come back on. What is the purpose ...
2
votes
1answer
54 views

How can i add a common “C” Wire to this old system?

I have an oil HVAC that was put in back in 1996. I sadly do not know the model of the furnace and cannot dig out any paperwork on it. Anyways, i want to go with some of the bells and whistles for a ...
2
votes
1answer
291 views

What could cause the furnace blower to come on constantly and no fire in gas burner?

When thermostat is turned up on my hot air furnace, the blower immediately comes on, blowing no heat, had it checked and with some luck the burner fired after about 10 tries of switching on and off. ...
2
votes
1answer
269 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 ...
2
votes
1answer
420 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 ...
2
votes
1answer
360 views

Could a high limit switch cause the furnace blower to run continuously?

My furnace was running fine. The I noticed that the unit was blowing cold air. Checked the furnace burners and they were off. I turned off the unit on the thermostat and the blower continued to run. ...
2
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2answers
117 views

Can I remove the insulation from flex duct

I am trying to fit a 7" flex duct between some floor joists and it would fit better without the insulation. Can I remove the insuluation and just use the plastic part?
2
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1answer
462 views

Is the furnace undersized?

I have a 2700 sq ft rambler home with cathedral ceilings over a large portion of it - over the hallway, 2 living rooms and kitchen. We replaced the furnace that was installed when the home was built ...
2
votes
1answer
2k 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, ...
2
votes
2answers
543 views

Is Flex Duct Safe To Use In A Crawl Space?

The home I purchased has a crawlspace below an addition that was put on to the original structure. The HVAC contractor that did the work ran 2 long runs of flex-duct to the 2 registers in the room of ...
2
votes
1answer
113 views

Can a problem with heater stack liner cause outside chimney mortar to crack and fall out

I had "high-efficiency" furnace installed in 2009. In 2011 chimney required full grind-out and repoint job, and chimney saver solution was applied to prevent water damage. Service lasted only 18 ...
2
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2answers
7k views

Does a compressor with a short to ground really require a complete system replacement?

My 24 year old home A\C went out some time Sunday morning. I had a tech come out and look at it, and was told that the compressor is shorted to ground, and that this means I have to replace the entire ...
2
votes
3answers
2k views

How can I repair an air conditioner drain line that is broken flush with the wall?

As you can see below, I broke the drain line off flush with the wall. There appears to be either a union or an elbow embedded in the wall with a broken off piece of pipe in the fitting. The joint ...
2
votes
1answer
3k views

How do we replace an old 3-wire thermostat with a 4-wire one?

How do we replace an old 3 wire thermostat with a 4 wire one? We have an AC/heating unit, but the wiring for the thermostat does not have a yellow wire. What can we do?
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2answers
821 views

Why does the pilot light on my Vermont Castings stove keep blowing out?

I bought a house with a sunroom heated by a Vermont Castings gas stove with a problem the HVAC/stove repair person hasn't solved by replacing the thermocouple, valve($$$) and taking apart and ...
2
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1answer
5k views

Why won't my Heil 7000 natural gas furnace ignite?

I have a Heil 7000 gas furnace Model: NUGK100DH12 Serial: L933050100 When we turn it on at the thermostat, the exhaust blower will kick on. We checked to be sure the gas is reaching the unit and ...
2
votes
5answers
15k 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 ...
2
votes
1answer
131 views

A/C Emergency Cut-off Cleaning and Maintenance

I found my thermostat not working. After googling for a solution, I found that I may need to check my emergency cut-off. I know of a pipe that if tripped will turn-off the A/C, so I took the pipe ...
2
votes
1answer
263 views

HVAC electric thermostat panel “goes dead” and then live again all the time

I have this digital thermostat controlling my heater (gas). When I turn it on to lets say 66 deg, and the house is at 60, the HVAC will start working of course. Problem: After few minutes, the ...
2
votes
2answers
1k views

How do I repair loose ductwork?

The ductwork in our 30 year old house has started coming loose where it comes up through the floor. It's nailed to the subfloor, but in several places, the nails have come loose, leaving gaps of an ...