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

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2answers
72 views

Rain water leaking around attic furnace

I bought a house a few months ago and when I bought it I noticed what appeared to be a water spot on the ceiling of the top floor. Of course I didn't do anything about it until heavy rains over the ...
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3answers
110 views

Is an HVAC license required for DIY home owner AC installation in the State of Georgia?

Does anybody know for certain if in the State of Georgia, an HVAC ("conditioned air") license is required in order for a homeowner to install their own HVAC system?
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2answers
97 views

Is the Thermostat Wiring Correct

When I moved in to the house the first thing I changed was the old mercury style T-stat to a digital one, I went wire for wire, and it has works (knocks on wood) so far. Now that I have been reading ...
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3answers
77 views

My Goodman a/c motor fails due to high voltage

I have got a brand new goodman unit. The motor kept stopping after few hours an the tech replaced the motor. It still had same issues.. I was told that the voltage coming into the unit is too high.. ...
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1answer
39 views

How to control system with 2 condersors+evaporators and 1 blower

I have problem with the control the HAVC system using 2 condensors + 2 evaporatora with one blower. I used 2 thermostats (4 wires/thermostat) to control. But the problem is when i turn on (cool ...
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1answer
80 views

central A/C Turns back on 30 seconds after shutting off

First of all, the a/c system is probably 30 yrs old. The outside unit stays running when the inside unit shuts off. After about 30 seconds, the inside unit turns back on again, and will sometimes only ...
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1answer
33 views

How can I plug a hole cut in a window pane for a portable A/C unit?

I just moved into a room where there is a portable A/C unit. To create a vent for the unit, a hole was cut in the glass of one of the window panes that spans about 13.5 cm. I was told that the unit ...
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1answer
281 views

Help installing new thermostat

disclaimer, this is my first attempt at doing any type of electrical work, so apologies in advance for any wrong terminology :) I attempted to install a new Honeywell programmable thermostat. When I ...
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1answer
86 views

Furnace is Sweating an Abnormal Amount

I noticed my furnace sweating a couple days ago. It's hot and humid where I live so I was only mildly concerned. It was a high of 74F today with humidity around 70% which is, relatively, nothing. ...
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1answer
67 views

Upstairs/downstairs cooling- leave it on or off?

It's 100+ here in Texas. My house has separate air conditioners for upstairs and downstairs. We rarely go upstairs, but I'm told that we have to account for air flow "chimney effect" up the stairway ...
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1answer
103 views

How can I prevent a secondary condensation drain line from dripping down the side of my house?

I have 2 central AC units in my 2 story house. From what I was told by the last AC repair man that visited, each of my ac units in the crawl space/attic has a main drain line that drains directly ...
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1answer
120 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
82 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
865 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
99 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
99 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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2answers
247 views

Why does my furnace run periodically when the thermostat is off?

I just moved into a small apartment that has oil tank / water baseboard heaters. At first the furnace would not come on at all, after hearing the "click" in the thermostat. Maintenence was sent 3 ...
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2answers
367 views

G to C trick not working for cooling. Honeywell RTH9080WF

My electric furnace has no c terminal. Furnace is heat & cool both. (Lennox Electric Fan coil Model CBS18-21-3P). I installed Honeywell RTH9080WF. I switched G to C on my thermostat and got the ...
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1answer
53 views

Difference in total pressure when HVAC system is on or off

This is a follow up question to one that I asked here. I am measuring the total pressure at the registers (all registers are open) with the BMP180 pressure sensor and somehow they don't change very ...
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1answer
596 views

Duct static pressure vs ambient air pressure

I've read that air handlers are typically rated for 0.5 iwc. Doing a simple conversion, this comes out to about 125 Pa. Is this with reference to the ambient air pressure? So, if I had an absolute ...
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3answers
191 views

Why does the outside fan stop but the blower fan continues to run?

We can have the thermostat set on 76 but wont stay 76 in house. Will come on when temperature is 79 in the house.
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1answer
51 views

Allergies and an economizer

I had an economizer added to my HVAC system last fall, which is fantastic for cooling my second floor down in the evenings during the shoulder seasons where the weather is cool in the late afternoon ...
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2answers
163 views

Why do I have to start my furnace manually every morning?

The oil furnace works fine all day and evening, then overnight I have the programmable thermostat lower the temperature at 11pm. But every morning at 5am when the thermostat tries to turn the ...
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1answer
200 views

What could be causing a moth ball like smell?

We have a smell like moth balls in bedroom of condo. Moth balls and camphor smell coming from heating unit in bedroom.
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1answer
130 views

What if my Trane 3 ton 13 seer heat pump is unable to generate enough heat to reach the set point on the thermostat?

The unit turns on when thermostat temperature is set higher than room temp. It blows cool air for several minutes and then the emergency heat kicks on and warmer air comes from vent. This lasts for ...
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1answer
304 views

Can a gas furnace be installed in an outdoor enclosure?

I have an old home in which ductwork has been retrofitted. The ducts for the first floor are arranged under the floor. The first floor is heated and cooled by an electric package unit sitting just ...
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1answer
250 views

Is it normal for the burner in my furnace to turn on and off during a single heating cycle?

During the heating time when the furnace is running to reach the temperature ask for, the burners will run for 3.5 to 4 mins.than shut off for 1 min. Then turn on again.it will do this until temp. is ...
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1answer
371 views

When to Replace UV Bulb in AC System?

We had a new AC system put in last summer. The contractor included a UV bulb between the cooling area and the supply fan. It's supposed to kill bacteria and other nasties in the air. (The bulb is ...
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1answer
691 views

Carrier 60,000 BTU 92% Furnace vs Carrier 40,000 BTU 95% AFCU Furnace

I have about 900 finished square feet in my house, and I'll eventually be adding another 200 or so finished sq/ft in my basement. I'm looking to get my furnace replaced and have been quoted two ...
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2answers
1k views

How do I calculate CFM for a structure?

This is for calculating the CFM (cubic feet per minute) of air that the blower needs to move in order to compensate the total heat loss (ventilation,infiltration,heat loss through walls, windows, ...
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1answer
246 views

Adding an on/off switch for my furnace fan

Here is my situation, I want to be able to run the blower on my furnace during the summer so that the cool basement air can be circulated thought the house. I live in an old house and the thermostat ...
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1answer
358 views

What could be causing my gas fireplace to shut off?

I have a gas fireplace that is 4 years old, that shuts off after a couple of minutes. The pilot lights ok, then the burners turn on and work fine for about 3 minutes. After that the entire fireplace ...
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1answer
161 views

Gable venting a bathroom fan and kitchen range hood

I am planning on venting my bathroom fan and the range hood in my kitchen out the gable end of my house in separate runs. The gable end is above a gable roof, so I am hoping for some recommendations ...
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1answer
878 views

Where is my common wire on the unit?

I have 2 systems in my house, my heat is gas hot water radiator heating and A/C is a separate newer system. I'm trying to figure out if I can run a C wire off air handler from the A/C system to run ...
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1answer
347 views

Which is better indirect or tankless hotwater heater

I am in the process of getting my boiler and hot water heater replaced. One company gave me a quote for a Weil McLain boiler and indirect hot water heater. Another company gave me a quote for a bosh ...
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1answer
137 views

How can I determine what grade air filter is appropriate?

I'm trying to figure out what kind of air filter is appropriate for my house. My local home warehouse store stocks over a dozen options. The primary difference between them seems to be Microparticle ...
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2answers
73 views

Is it possible to create a better temperature controlling system?

I have a two story 2.5k sq ft house with a varying degree of temperature throughout the house. The main problem is that the air coming out of vents are very weak if almost nil. Only the living room ...
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1answer
154 views

Should my A/C compressor come on when I turn only the fan on?

I have a bog standard HVAC system with a Nest thermostat. When I tell the theromostat to turn the fan on for 15 minutes the A/C compressor also kicks on. Is this normal?
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1answer
351 views

How to connect a DIY thermostat to the HVAC System

I am building a DIY thermostat similar to this blog. I want to connect it to the HVAC system of my home. How do I do that? I found this post which is very informative but doesn't completely answer my ...
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1answer
94 views

Should I add an escape register for added ventilation in A/C duct to reduce condensation?

I have a condensation and drippage problem where my 8" exposed circular AC duct comes out of the ceiling. Above the ceiling is the attic, meaning it gets pretty hot. The pipe comes out of the ceiling ...
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1answer
1k views

Air Conditioner woes: water pooling in basement, condensation on ducts, frost on outdoor copper pipe

Can someone help diagnose what's wrong with my air conditioner? The symptoms are: the air that it is blowing is not very cold It's colder than the ambient air, but not cold enough to cool the ...
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1answer
103 views

AC unit (turned on year round) leaves so much ice in the blower causing no cooling (pic included)

My mother has asthma and tells me she needs the AC on almost year round. The AC unit is outside the condo we own, and it connects to the coils in the heater/ventilation system. We are experiencing ...
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2answers
318 views

What size A/C unit should I install?

currently using a Goodman 24000 BTU Central air, installed in '96. it is starting to cost too much because of leakage of refrigerant. I did the size calculator thing and it recommends a 30000 BTU ...
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1answer
221 views

What could be causing our air conditioner circuit breaker to keep tripping?

Our air conditioner circuit breaker marked "AC", is tripping frequently after the AC unit works for a while. Sometimes as long as an hour or more and, sometimes as short as few minutes. We were told ...
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1answer
1k views

How well does a single A\C unit provide 2 zone cooling?

My 2,900 square foot house currently has two separate AC systems (one upstairs, one downstairs). They're both very old and need to be replaced. One of the four HVAC salesman that provided quotes ...
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3answers
179 views

What are the possible reasons I am not getting cold air from my air conditioner?

my heat pump outside is working but my central air conditioning/heating unit in the garage makes a hissing sound or faint sound of water running. There is air coming from the vents. The very last time ...
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1answer
5k views

Quieting cold air return vent

My gas furnace is in a dedicated "closet" inside the utility room. The closest cold air return is about 5' away (laterally) in the ceiling of the hallway right by the bedrooms. When the furnace ...
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1answer
232 views

Should I remove existing drywall before framing a wall around HVAC ducts?

My friend has soft AC ductwork running up an interior wall. He wants to build a wall around it to hide the ductwork. My idea is to pack out the wall by nailing in framing between the ductwork right ...
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1answer
2k views

I have just reset furnace due to a trouble code, what should I monitor or re-do over the next few days?

My furnace was throwing a trouble code. The code was 31 and for my manufacturer (Bryant) and others thats is a pressure switch code. I was able to resolve this code and get my heat back on simply by ...
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1answer
162 views

Does HVAC lineset need to be grounded?

My HVAC contractor says the installation of the line set between the air handler and the condenser outside is complete but he has not grounded the lines. Do HVAC copper pipes need to be grounded?