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

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4
votes
1answer
9k views

How can I prevent my HVAC condensate drain line from freezing?

Last night, my heat (forced air) suddenly stopped. Today, a plumber figured out that my heater is 90% efficient, produces lots of condensate, and the drain line had frozen. We went outside and saw ...
1
vote
2answers
2k views

What could be causing this leaky evaporator problem?

My apologizes if I do not know the correct terminology for some of the parts. I will try my best though. We have a Trane A/C system that is causing us a headache. It is causing water damage in our ...
1
vote
1answer
148 views

What does the low limit do, and where should it be set on an oil fired hot water furnace?

What does the low limit do, and where should it be set? My furnace has a honeywell triple aquastat relay and has a difference dial. Water temp is about 190 deg F. Also, water psi gauge is only ...
1
vote
1answer
190 views

Why won't my propane boiler's pilot stay lit after replacing the thermocouple?

The pilot on my propane boiler won't stay lit for more than 30 minutes even after replacing the thermocouple and outside gas valves. The inside gas valve was replaced two years ago. Service people ...
1
vote
0answers
428 views

What's causing my draft inducer to stay on?

I have a new, 3-year old, high-efficiency, gas furnace in my home. I recently realized that my draft inducer, which normally kicks on before the burners and before the main blower, is not stopping. ...
4
votes
3answers
4k views

What's causing the rumbling sound when my furnace kicks on?

I have a new, 3-year old, high-efficiency furnace in my home. Last year it started making a slight whining noise that was audible during the very first stage, before the blower motor started. No ...
2
votes
3answers
1k 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)?
1
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2answers
300 views

Is a PTHP a HVAC option for a super insulated structure?

Is a Packaged Terminal Heat Pump a good HVAC system for a structure that is super insulated or passively insulated assuming the unit is sized and fitted to meet the needs of the structure. There is ...
3
votes
2answers
1k views

Is voltage too high in C wire going to thermostat?

I've managed to add a C wire to my thermostat. I then decided to check the voltage between the R and C wires, and find that it read as 27.8 volts, not the 24 volts it was supposed to be. Could this ...
0
votes
1answer
504 views

How do I turn off the power to my programable thermostat?

I am installing a new programable thermostat. In trying to cut power to the old one I have tried a couple of things but not sure I have done enough to cut all power. One, I shut off the furnace ...
2
votes
2answers
6k 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. ...
0
votes
1answer
252 views

How can I replace a 4-wire manual thermostat with a programmable thermostat?

I"m replacing a 4-wire manual baseboard thermostat with a programmable SBFT2W thermostat. After connecting the wires, there are two lead wires from the old stat that are still unconnected. They are ...
4
votes
3answers
2k views

Why does the pilot light go out when the furnace is running?

Every time the furnace fires up, it blows out the pilot light. Sometimes it will run a full cycle and blow out when it shuts down, and sometimes it will blow out about a minute into the cycle. We ...
2
votes
2answers
7k views

How can I prevent my house from smelling of smoke after having a fire in my fireplace?

We have a wood-burning fireplace in our family room. Fifteen feet from the fireplace is a large cold air return. When the fireplace is stoked, nice and cozy, everything is fantastic. When I shut it ...
1
vote
1answer
122 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 ...
-3
votes
1answer
882 views

why won't my furnace turn off once it reaches the desired temperature

I have a moncrief furnace and replaced the thermostat but the furnace will not cut off once it reaches the desired temperature. What could be wrong?
4
votes
3answers
803 views

How can I redirect the discharge of my forced air vent?

An AC/heating register on our kitchen ceiling blows air directly toward a gas cooktop causing the flames to flicker. Adjusting the register doesn't seem to make a difference. I've looked into air ...
-1
votes
1answer
317 views

Why do I have a large PVC pipe venting warm air outside intermittently?

There is a large PVC pipe (3 actually) which vent air intermittently. I started noticing I could see steam rising over my deck in the morning and then I found that these pipes vent air at least a ...
1
vote
0answers
51 views

How can I add a common “C” wire to my thermostat? [duplicate]

Possible Duplicate: Options for adding ā€œCā€ wire to thermostat I recently bought the Honeywell THM5320R Wireless thermostat. After going to hook it up I found what many others have, it ...
4
votes
2answers
734 views

Do joints in adjustable duct elbows need to be taped?

Do the joints in adjustable duct elbows need to be taped as well once they're adjusted or are they considered air-tight?
3
votes
1answer
403 views

How do I support vertical runs of round ducting?

Supporting ducts horizontally seems pretty straight forward--just a loop of strapping underneath to support it. What about when the duct runs vertically? Do you use the same kind of strapping but ...
8
votes
1answer
288 views

Should I relocate the HVAC unit in my attic?

I have had a couple of estimates to replace our HVAC system and one contractor says he would relocate the system to a more central location in the attic. One says there is no need to relocate. There ...
1
vote
1answer
2k views

How to connect Nest in Europe

I found a question regarding the Nest thermostat here. But that is only a question "Will it work?". Thanks to that I know it WILL, the problem is...HOW. I know the wire naming conventions are ...
0
votes
0answers
84 views

I have no furnace, only electric blowing heaters. How do I get ventilation?

I have a 100 years old building with a store on the main floor. Since the building was built over 100 years old there is no ducting whatsoever. There is also no furnace. In the summer we just hook ...
3
votes
2answers
363 views

Can a HVAC solve my ventilation problem?

I have a problem with my house such that with all my windows and doors closed the house smells and the air feels stale. I'm thinking of purchasing a high efficiency HVAC to vent the stale air out and ...
3
votes
2answers
4k views

Should my thermostat's blue wire be going to W2?

I've recently moved into my first house and am looking to replace the existing basic thermostat in the home. Here is a picture of how I found it wired: Researching the wires, I've read that ...
2
votes
1answer
3k 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
1answer
310 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
4answers
8k 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 ...
1
vote
2answers
20k views

Why won't my A/C turn on after I replaced the thermostat batteries?

Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the LCD screen was operable, our AC no longer turns on. I have attempted a factory reset on ...
5
votes
2answers
1k views

How to best keep floor vent by shower dry/mold free?

We just moved into a rental home. It turned out after living there for a few weeks that we discovered the vents were innudated with mold. They were so bad the landlord had to replace all the vents in ...
0
votes
2answers
1k views

What could be wrong with my A/C unit?

I just installed a new compressor fan on my outdoor A/C unit. Before the fan went bad, it was working fine and had just had its annual service check (the service guy said the freon was fine, ...
2
votes
1answer
1k 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
1answer
613 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 ...
5
votes
2answers
3k views

Should I be concerned about fridge/freezer airflow?

We just recently had the following counter/cabinet system put into our basement family room. After everything was done, I started to get concerned about airflow. The enclosure was built in such a ...
3
votes
1answer
3k views

Convert line voltage heating system to use low voltage thermostats

I currently have two line voltage ceiling radiant heating systems in my condo each with their own DPST thermostat. I'd like to use low voltage thermostats such as the nest. I found this ...
4
votes
2answers
1k views

Are there high flow floor heat registers available?

The weather has been pretty warm lately so we've been running our A/C. I noticed that it didn't seem like much air was coming out of the registers, so I checked to make sure the blades/louvers were ...
2
votes
1answer
105 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 ...
3
votes
1answer
316 views

Is it OK to shut off the A/C at the breaker?

My A/C continues to run even after the thermostat says it should shut off. Can I shut off the A/C by tripping the circuit breaker until it can be looked at? Is there any safety issue with doing this? ...
3
votes
1answer
281 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 ...
6
votes
3answers
1k views

How do outdoor mist-cooling A\C units fare in real-world usage?

I live in Phoenix where summer outdoor temperatures regularly exceed 110°F and humidity around 15% or lower is not uncommon. In this environment a mist system can easily pull the temperature down ...
2
votes
1answer
4k 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 ...
2
votes
1answer
1k 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 ...
1
vote
0answers
652 views

How can I properly drain heatpump condensate?

I have a heat pump in the attic That drains to the ground outside two floors below. I naively added a hose fitting so I could redirect the water where I wanted it, slightly up hill. This created a ...
2
votes
3answers
8k 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 ...
4
votes
0answers
130 views

When cleaning HVAC ducts, is treatment for fungi and bacteria routine and mandatory after 20 years? [closed]

Is treatment for fungi and bacteria routine and mandatory after 20 years? Or should we test for fungi or bacteria first? This would be in addition to air duct cleaning.
2
votes
3answers
2k 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 ...
1
vote
2answers
879 views

Is there a filter-reminder thermostat that uses run-time instead of total time?

My HVAC filter is in my crawlspace and is a hassle to change. I don't want to change it more than needed. "Change it every month" is bogus advice because in some months (like May) we don't have to run ...
4
votes
1answer
2k views

How should one size ductwork for a new air return duct?

I recently had a contractor build a wall which split one room into two. The new room is an office with two computers, and four monitors. It gets very, very hot, until the air conditioning turns on, ...
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 ...