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

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1answer
120 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
827 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
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3answers
750 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 ...
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1answer
310 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 ...
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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
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2answers
704 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
386 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
280 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
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1answer
1k 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 ...
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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
348 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
3k 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
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1answer
2k 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
301 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
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4answers
7k 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 ...
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vote
2answers
18k 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
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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
576 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
2k 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
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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
311 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
279 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
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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 ...
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0answers
639 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 ...
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0answers
129 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
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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 ...
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vote
2answers
852 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 ...
3
votes
3answers
14k views

How much less power does a three-phase A\C unit use as apposed to a 220v unit?

I'm planning to install a 5 ton central AC. I'm deciding between a condensing unit that runs on 220V and a costlier unit that runs on 207Y three-phase. My understanding is that three-phase motors use ...
2
votes
2answers
325 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 ...
3
votes
2answers
3k views

Can I increase air volume by adding more fans?

I have a straight 25 foot rectangular duct that is 0.9 sqft in cross-sectional area (11" by 12"). There are openings on either end, and nowhere in the middle. I wish to move about 1000 CFM through the ...
6
votes
3answers
3k views

How can I determine why my A/C runs all day?

I have a Bryant AC/Furnace unit. My house is 10 years old. A heat wave hit this weekend & temps got up to 95°F outside. I had my thermostat set to 75°, and it ran all day. The ...
8
votes
1answer
2k views

How do you trigger the hvac with wiring only?

I have a HVAC that has the usually wiring C R G W Y Pinouts What wires do I need to connect to turn on Heating? What wired do I need to connect to turn on the A/C? Is there a risk of damaging any ...
1
vote
1answer
159 views

HVAC unit won't come on

This morning I noticed that my main floor wasn't cooling. I found the condensation pump full ( little giant model VCMA-15ULS ). I disconnected the hose from the unit to the pump, drained it, dumped ...
2
votes
1answer
227 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?
3
votes
4answers
6k views

How can I connect two indoor ductless A/C's to one compressor?

I have one Hitachi i-clean split AC 2ton unit installed in my home. I want to connect another indoor ductless unit to the already installed outdoor compressor. I only need to use one indoor unit at a ...
3
votes
1answer
494 views

How can I protect A/C condenser wires?

I bought a replacement condenser fan motor for my outdoor A/C unit. The old unit was CW direction only. This one is CW/CCW and has 4 wires stick out of the side that change direction depending on how ...
5
votes
1answer
889 views

Do I need to increase my HVAC trunk line size?

I'm thinking of finishing my basement. I currently have a main trunk coming off my furnace that measures 20" wide by 6" tall. I'm trying to future proof my home in the event my current furnace can't ...
2
votes
1answer
2k 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 ...
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vote
1answer
3k views

AC Unit Blow Warm Air Indoor But Colder Air Outdoor

I have two AC Units. One for upstairs and one for downstairs. The upstairs one works just fine but not the downstairs. So, i did a test by turning both units on and went outside to compare the two ...
2
votes
1answer
143 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
1k 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 ...