(Heating, Ventilating, and Air Conditioning) For questions about installing, repairing, and troubleshooting HVAC systems.
2
votes
1answer
2k views
How can I add a “C” common wire to this system?
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
2answers
2k 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 ...
5
votes
1answer
332 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
394 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
332 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 ...
4
votes
0answers
99 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.
7
votes
3answers
794 views
Are new “low noise” whole house fans actually quieter?
I've dealt with a number of older whole house fans (10 years and older) and the one thing they all had in common was a ton of noise.
Are the new "low noise" fans actually that much quieter than the ...
1
vote
2answers
348 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 ...
3
votes
3answers
4k 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
1answer
708 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
2answers
126 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
879 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 ...
5
votes
3answers
745 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
439 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 ...
0
votes
1answer
117 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
133 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
1answer
248 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
437 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 ...
3
votes
3answers
1k views
Can I sense filter replacement need based on filter pressure drop?
I should first point out that the system I'm referring to will be a self build DIY project. Fan and Filters being the only items purchased complete, And I'm still in the design phase but I'm not a ...
1
vote
1answer
545 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 ...
1
vote
1answer
528 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
421 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
1answer
135 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?
5
votes
1answer
111 views
Does lack of zone control delay hurt heat pump?
I had a new HVAC single heat-pump system installed with dual zone controls:
2 thermostats and 2 dampers for separate zones.
The system works, but the zone control board does not have any time ...
4
votes
3answers
283 views
Advice for replacement/repair of an HVAC with a cracked heat exchanger?
My townhouse has a downflow 1994 Rheem 2.5 ton HVAC unit on its roof (combines both A/C and heat). We have had two issues with the unit and have been in the townhouse for a little under two years. In ...
2
votes
2answers
786 views
$400 electric bill traced to heater - what could be wrong with it?
Back in December/January, we got a real shocker; a $400+ electric bill. I thought there must be a billing error, so I went out to the meter, and found that not only was the number probably right, we'd ...
6
votes
2answers
6k views
What are the pros and cons of two AC systems vs a dual zone system?
I have a Cape Cod with 1000 ft2 on the first floor and an apartment in the attic. In a few years I may get rid of the apartment and build up a second story + attic. Both the first floor and the ...
4
votes
2answers
657 views
What are these two pipes coming out of the house?
I am trying to figure out the purpose of a couple of pipes that are currently coming out of the house.
First, a couple of notes:
One-story house.
HVAC system is in the attic.
It is winter here. ...
5
votes
1answer
409 views
Is there a wireless thermostat that will make relocating easier?
I've got a single zone which covers all three upstairs bedrooms in my home and the thermostat is located in the master bedroom. We prefer it to be somewhat cooler at night, but the baby in the ...
5
votes
1answer
172 views
Is it possible to recover waste heat from a boiler?
I did a google search and came back with industrial products, but no residential prosucts.
I have a System 2000 boiler and hot water tank. When the furnace is firing, the temp of the exhaust through ...
4
votes
1answer
271 views
What could cause a furnace to short cycle?
My Ducane MPGA100B4B furnace is shortcycling (2 minutes from fan on to fan off)
The thermostat's Heat Anticipator setting doesn't seem to matter for the on-time, maybe the offtime changes
The ...
4
votes
1answer
776 views
What would cause my furnace to only work with the filter removed?
My Carrier furnace works fine without the air filter in place on the return. With the filter in place it works for a while and then stops with a complaint about "limit, or flame rollout is open" ...
11
votes
3answers
2k views
Ethernet cable instead of Thermostat wire?
I need to pull new wire from my furnace to my thermostat and was wondering if there would be any problems in using an Ethernet cable instead of standard thermostat wiring.
The reason being is I have ...
2
votes
1answer
279 views
Replace 7“ metal duct with 6” flexible or 8" flexible?
I am replacing the flexible ductwork in my attic, which is a mix of ancient 6" and 7" metal ducting. I'm having a hard time finding 7" flexible ductwork for sale locally, but no problem with 6" and ...
0
votes
0answers
217 views
new furnace installed - few questions
So, Sunday the fan on our 18 year old furnace died; instead of paying the $600 to get it repaired, i opted to buy a new one.
Lennox SPV98UV (i think) 98% efficient / variable speed fan. they ...
3
votes
2answers
287 views
Why is my furnace filter alarmingly clean?
I have central air and heat at my appartment I moved into about 6 months ago. Today I decided it was probably long past time to figure out how to change filters in the furnace so I poke around until I ...
2
votes
3answers
2k views
Why is my furnace blower noisy when it starts?
The blower of my furnace makes a loud noise every time it starts. I understand that a large fan and the movement of large amounts of air will produce some noise. What I am puzzled by is the noise that ...
2
votes
1answer
923 views
What would cause a furnace to shut off prematurely?
I've got a Carrier Weathermaker 8000 furnace that shuts off about 90 seconds or so after ignition, started doing this recently. I get flashing code "33" which indicates:
The code indicates:
33 ...
1
vote
2answers
390 views
How do I disable a thermostat to prevent it from turning on the AC?
I need to disable my thermostat from turning on the AC. Yes, covertly. I think one of my housemates is missing his native Antarctica. So, the thermostat still must be active & setable, but I want ...
3
votes
2answers
1k views
Is a lip necessary on an HVAC ceiling register boot for use with flexible ducting?
I've installed some new ceiling register boots to use with flexible ducting and realized after install that they have a smooth connection with no lip. I'm assuming they are made for metal ducting, as ...
2
votes
2answers
531 views
How do I lower a cold air return from the ceiling for a basement rental?
I am living in the basement level of a rental unit with forced air heat. There are 9 heating vents and one cold air return, all of which are in the ceiling. The air isn't mixing very well resulting ...
4
votes
2answers
2k views
Can I run heating duct work through the attic?
Problem...
(in Buffalo NY)
We just about finished remodeling our master bedroom. Everything insulated, drywalled and we're living in it.
Now that the winter is upon us, we're already finding this ...
3
votes
1answer
382 views
How do I replace an A/C diffuser attached to flex duct?
Our house has central air, with the air distributed via flex ducts around the house. On the second floor, the diffusers have baffles behind them that can be closed when the system is not in use, but ...
1
vote
1answer
458 views
What are my options for venting my oil boiler?
I have a small New Yorker AP-U (480?) boiler that is currently vented to a large flu in my house's chimney. I want to install a wood stove in my house and I'd like to use the chimney to vent it, which ...
1
vote
3answers
279 views
Is there a special low temperature thermostat?
I have a gas ceiling mounted furnace for my garage.
I want to set my garage at 35-40° F (1-4° C).
Is there a special thermostat to control furnace at that low temp? (I've seen one works as low as ...
4
votes
2answers
590 views
Where should I install a Pellet Stove to supplement my boiler?
We are purchasing a pellet stove insert for our single floor 1200 sq. ft. home. We are doing this to reduce our dependency on oil (hot water boiler), which we use to heat the house with baseboard hot ...
3
votes
1answer
83 views
It is reasonable to expect a contractor to replace the last foot of HVAC duct work, the connection between the insulated duct and the register?
The contract was to replace an antiquated HVAC and duct work. Since the registers are a standard size, would this connection also be a standard pre-fabricated part?
What is that last connection ...
4
votes
2answers
458 views
What are effective ways to frame a return air duct?
Consider an in-floor return air duct that is 32" x 22".
A standard air filter that closest fits the register is 30" x 20".
What materials should I use to frame the duct so it will snugly hold the ...
1
vote
3answers
253 views
Are 5" thick filters for furnace/Central AC still available?
My furnace/AC was installed about three years ago. It uses 16" X 25" X 5" filters. The problem is when I try to find a replacement at my local home center: at Lowe's, Home Depot, (you name it), I ...
5
votes
1answer
2k views
What's the most common cause of AC coolant lines freezing?
I noticed my house wasn't getting under 75°F this weekend when I had the thermostat set for 70°F. Since I'd done a lot of drywall sanding inside recently, my first idea was to replace the filthy air ...
