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

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1answer
127 views

Why would my house be so humid even when the A/C is running?

I live in Florida which this year has been particularly hot and humid. However, a while back I noticed mold in my closet and a very musty smell in my living room. Actually I even found mold growing on ...
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1answer
188 views

Water Heater Gas B-Vent Install

I installed a new water heater and want to vent it right. The old water heater used ABS pipe since it had a blower. Basically I have a 3" b gas vent pipe coming in and connecting to a flex gas pip ...
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1answer
75 views

Can dehumidification be achieved in a typical US residential forced-air system without dedicated components?

We have a very typical forced-air HVAC system with a medium-efficiency gas furnace and split-system central air conditioner in our house; however, latent load buildup (i.e. stickiness) is a problem ...
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1answer
750 views

Why would the condensing unit fan shut off but not the compressor?

We have an allegiance 12 unit circa 2001, model 7a2024a100a3, the fan starts up and runs for about 5 minutes then shuts off, the compressor is still on and seems to build up a bit the "flush" or so it ...
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0answers
72 views

Furnace not working

I came home to my furnace having no power even to show trouble codes. I turned off my breaker opened the blower door and it had a blown 5 amp fuse on the curcuit board. I replaced the fuse turned the ...
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2answers
117 views

2 PVC Pipes running from unit to basement

I have two 2" PVC pipes running from outside (AC unit) to the inside set up (furnace?). I need to cut these pipes and re run them since they are blocking the water heater which I need to take out. I ...
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1answer
96 views

Should I add a return or another supply to a large room with only one supply?

I just moved into a new house and I have that one room that always seems to be hot. It's on the 2nd floor of the house with the attic over it. The other 2 rooms on the 2nd floor are always a nice ...
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0answers
48 views

Why does my furnace blower motor stop working after 20 minutes?

The furnace blower motor stops working after 20 minutes, but the central air unit outside continues to run. The blower motor will not start again until after it has cooled off or unless I assist the ...
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1answer
189 views

Chattering contactor, what should voltage be when AC is on/off?

I have a Nest thermostat that I believe is the culprit of this issue. I've already replaced the contactor once and now the new one is chattering and not kicking the AC on. When the AC is turned off, ...
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0answers
60 views

What could cause a 5 ton Goodman packaged unit on the roof to turn on and off randomly?

With the thermostat on cool and manual the unit (fan + compressor) will turn on sometimes right away, and sometimes after hours. Then it'll run for either minutes or hours before turning off, either ...
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0answers
71 views

AC fan not turning on. It's silent

Replaced the capacitor 2 weeks ago because AC (Lennox) outside fan was not running, blowing in warm air. And the unit started working. Then again yesterday (95F outside) same thing. Replaced the ...
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2answers
520 views

Is there a way to turn on the air conditioning only on certain days?

We're looking for a way to turn on the air conditioning at our camp, say on a Thursday night, so that it will be cool when we arrive on Friday evening, but to shut it off if we don't go to the camp ...
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1answer
204 views

Closet where AC/Heater fan is located is very cold

I noticed that the closet where my heating unit/AC fan lives is super cold. I measured the temp using a black and decker IR thermal leak detector and the temp in the closet is about the same temp as ...
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1answer
3k views

Blower fan works w/ heat “auto”, not with a/c “auto” or on “on”

I've read the posts with the opposite issue, which have been helpful (you guys are amazing!) but still no solution. Problem is that the blower fan does not come on when system is on "Cool" and fan is ...
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1answer
492 views

Why would a blower motor work with A/C, but burn out with furnace?

I've gone through 2 blower motors since I purchased the home 3 yrs ago. I never have an issue with the blower when the AC runs; but it keeps dying in the winter with the furnace. I've had 2 HVAC ...
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1answer
613 views

Are my outside HVAC units and condensation drain PVC pipes set up correctly?

I'm a newbie with this stuff, but here's my situation: I have two HVAC units in my home. One sits on top of the patio and one sits on the ground. Both of them are draining condensation from the PVC ...
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2answers
828 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 ...
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1answer
163 views

Why is there a supply vent in my unfinished basement?

Background I have an unfinished basement. It has cement floors with stone walls. The furnace is located in the basement. There is a supply vent blowing conditioned air into my basement. As far as I ...
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3answers
99 views

Ac unit set on 74

My central air is set at 74. Yesterday and today, the house was up to 80. It has been very hot outside(90). Would this affect my ac unit?
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1answer
172 views

noisy Air-conditioner compressor

I bought a new split AC that worked great for a week or so, but now I can hear some annoying noise coming from the outdoor unit. The outdoor unit in installed on a flat roof so I can hear this noise ...
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2answers
167 views

Blower motor lost RPMs after reversal of fan direction

My air handler requires a clock wise rotation of the fan motor. After installing a new motor I found it was set in the counter clockwise position. I changed the wires (switched inline connection on ...
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0answers
112 views

How to connect honeywell wifi thermostat to trane A/C unit

My current system has 4 wires to the thermostat. I need to add the C wire for the new honeywell wifi thermostat. On the wiring board of the a/c I found 26vac on one terminal. The red wire to the ...
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6answers
4k views

Air Conditioner Can't Keep up

We just rented a condo and our A/C cannot keep up so it will run almost constantly. It can't even keep the temperature constant, it will creep up into the 80s even while running. I measured the ...
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2answers
2k views

How can I wire my WIFI thermostat to control my millivolt fireplace?

I have a gas fireplace that has an millivolt on/off switch on my wall (and a remote that includes flame on/off, a countdown timer and a thermostatic flame control). I want to be able to program ...
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6answers
6k views

Do I need to level the outdoor AC cooling unit?

I've read somewhere that the outdoor AC unit needs to be leveled. My outdoor unit is a bit slanted due to the floor not being completely flat (pic below). However, I don't see any obvious structural ...
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0answers
107 views

Will a DIY Air Conditioner help my HVAC Central Air system?

So the husband and I just moved to Texas. We went away for the weekend and turned our HVAC central air from 68F and ON to 75F and AUTO. For some reason when we got home the AC wouldn't drop. Now I ...
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1answer
157 views

How can I better control temperature differences between floors in my two story home that has two HVAC systems?

We have 2600 sq ft on the main level and 800 on the 2nd floor. To the 2nd floor, there is a staircase and with a door on the bottom floor. We have our master upstairs and don't use the room at all ...
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2answers
2k views

Why “extra” power disconnect for small HVAC unit?

I am in the throes of learning enough to do a DIY install of a small heat pump package unit. The installation manual calls for (and suggests that NEC requires) a "fused disconnect" inline with the ...
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1answer
2k 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 ...
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0answers
29 views

Thermostat and thermostat system for small business with several units and tenants

Am the facilities guy in a small church and pre-school. There are 8 heat pump units through out the church/schoool. Each has a stand-alone thermostat and they are all different. I would like to get ...
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1answer
142 views

How to connect thermostat to newly-installed condenser/evaporator unit

I installed a furnace evaporator and condenser brand goodman 4 ton unit but need to know how to connect thermostat from condenser to the furnace to the thermostat if any suggestion.
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1answer
259 views

Why would my zone controller be displaying error: AC voltage insufficient?

Our AC unit was new with our house and is only 7 years old. We have a split zone system controlled by a Honeywell HZ322. Today we had no AC so I started looking at possible issues. When I got to the ...
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2answers
190 views

Window AC not cooling

I've GE window AC 0.75 ton it has stopped cooling I cleaned the nylon net properly with old tooth brush,it was totally blocked Then I combed the metallic horizontal fin like structures which were ...
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1answer
80 views

What is causing this air-conditioning unit to cool on cold days?

This is a temperature log from a reverse cycle air conditioning system that has run fine for getting on for 30 years. It has suddenly started to blast out cold air on days when it should be heating. ...
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1answer
725 views

Is installing a packaged HVAC unit (PTAC) a realistic DIY project?

I'm a handy guy and can do pretty much anything around the house that I put my mind to. Assuming I can handle the part of the install that is outside (the concrete pad, the hole in the crawlspace ...
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2answers
205 views

Issues after capacitor replaced on AC unit

Had a checkup on my AC/ furnace a couple weeks ago. The technician said the capacitor leaking oil and not pulling enough amps. He recommended me getting a whole new system. (My house was built 6 yrs ...
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0answers
37 views

Should I get a single- or two-stage furnace for my three-floor brick home?

I just bought a house that has a furnace on its last legs. The house is 1941 masonry in Chicago with 3 floors: finished basement, first floor and a second floor that is a converted attic with vaulted ...
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1answer
74 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 ...
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3answers
280 views

Do I need a neutral wire when connecting a 240V device?

So this is still not very clear to me: I am trying to get 240V to an appliance that does not need a plug (direct wiring), I won't need a neutral wire, is this right? In fact there is nowhere to ...
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3answers
303 views

No AC. I have a few HVAC troubleshooting questions

I'm having issues with my AC. Basically, the symptom is that I feel cold air coming out of the vent, but it has no pressure, almost like I have to put my hand IN THE VENT COVER to feel any cold air. ...
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1answer
1k views

ecobee3 Installation - Thermostat Y Terminal (yellow) Wire Connects to C Terminal Board

enter image description hereI'm attempting to install a new ecobee3 on an older Coleman Evcon gas furnace and AC HVAC system. The system is what I would consider typical residential as far as I can ...
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0answers
178 views

My A/C Unit stopped working after replacing blower motor

Any idea what I may have done wrong here or how to check? I replaced my blower motor (it was 100% compatible and had the proper capactitor), and upon starting it up the blower did nothing and the A/...
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0answers
43 views

Should I install a doorway fan or dehumidifier?

I have central air in a rancher (one floor), and the living room is on one end of the house. That room is on a slab, and has always been noticeably hotter in the summer and colder in the winter than ...
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2answers
339 views

lennox AC condenser Fan running backwards

I have been trying to figure this out for a little while and about to check into the nutty house!! The Condenser fan went bad in my AC Unit. It was a 3 wire motor. I got a Universal replacment motor ...
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2answers
10k 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 ...
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0answers
45 views

Residential HVAC: one main thermostat, what do the other thermostats in the rooms do?

Are the other thermostats only meant for non-force air heat only? Does it mean only one thermostat in the house needs to have both heating and cooling, and auto or fan-only switches? It sure make ...
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1answer
680 views

WIFI thermostat no C wire

I hooked up a Honeywell WiFi thermostat last fall. There is no C wire in the furnace & the Honeywell rep suggested I wire up a small separate transformer with new wires going to the C and RC ...
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0answers
190 views

replacing single pole York A/C contactor

I am trying to replace a single pole contactor with burned contacts on York package unit Model D3YS030N064069. The old contactor has four 24 volt lugs on one side. The new contactor has 2 on each side....
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1answer
416 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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1answer
106 views

Is my AC right-sized for my house

2 years ago I had a Bryant 2 Ton 13 Seer Air Conditioner + new furnace and coils installed in my 2800 sqft ranch style house with 6 bedrooms and 2 baths split evenly between the basement and main ...