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

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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
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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
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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 ...
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3answers
2k 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 ...
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3answers
880 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 ...
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3answers
1k views

How can I reclaim heat from an enclosed furnace room?

Our home has two furnaces (oil fired hot air) and an electric water heater in an enclosed room (approx 6'6" x 9'). Three walls of the room divide it from the remainder of a finished basement, the ...
7
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2answers
3k views

Why are almost all of my house's HVAC floor registers placed near exterior windows?

My current house is a single story built over a crawlspace and all the HVAC registers are in the floor. In all of the larger rooms, at least one (and usually more) register was placed near an exterior ...
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2answers
2k 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 ...
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1answer
253 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 ...
2
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1answer
308 views

Will I see any performance gains if I reconfigure my thermostat to control the second stage of my 2 stage furnace?

Our furnace is a two stage one that was installed last year (a Bryant 80t). When it was installed, it was installed with a thermostat for a one stage furnace. This appears to be because this model ...
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2answers
2k 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. ...
4
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1answer
436 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 ...
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1answer
1k views

How can I prevent heat loss through heater/air conditioner wall units?

HVAC experts out there... I live in Wisconsin and it gets mighty cold here! I have a condo with 2 wall units that are used for both air conditioning and heat. My heat bill in the cold winter months ...
5
votes
2answers
817 views

Is it safe to install a sconce light box inside a return air space?

In my finished basement, the space between one section of studs is being used as a return air duct for my furnace and central air. Here is a picture, looking up from the vent at the floor level: ...
4
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1answer
2k 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
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3answers
4k 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
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1answer
455 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 ...
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2answers
1k views

Can an HRV replace the air exhausted by a range hood?

I'm in the process of buying a 1950s ranch house. It doesn't have the greatest insulation, so I'm planning to do some improvements over the first few years to tighten things up. I'll certainly do the ...
3
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2answers
837 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
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3answers
5k 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 ...
3
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3answers
4k views

Can I using a 3-phase connection to power 1-phase AC unit?

I have preparation for an AC connection with 3-phase 220V 3X16A breaker. I want to install a 220V 1-phase unit, which also needs a 16A breaker. The physical connection has screw-on terminals, so there ...
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4answers
127k views

How can I add a “C” wire to my thermostat?

So, the spiffy new wi-fi thermostats want power on the C wire from thermostat, but the old thermostat doesn't have a C wire at it. What's the easiest way to add the C wire/24 volt to the thermostat ...
4
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1answer
1k views

Can I reroute this air duct?

I'm quite new to dealing with HVAC duct-work. We would like to install a suspended ceiling in this room. Since the finished ceiling will be higher than this duct-work, we're going to build drywall ...
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2answers
2k 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 ...
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2answers
970 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 ...
5
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1answer
132 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 ...
3
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2answers
3k 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
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2answers
808 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 ...
3
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1answer
786 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 ...
4
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2answers
3k 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 ...
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1answer
793 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 ...
3
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1answer
153 views

How to find this particular hot water heat pump?

I have this pump pictured attached to my furnace. I actually have two of them. This one, however, is on a circuit that has been empty for a few years and is now rusted shut and needs replacing. I have ...
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4answers
515 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
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2answers
772 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
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1answer
102 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 ...
14
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4answers
10k views

Why don't programmable thermostats automatically switch between “Cool” and “Heat”?

While I can set my house to be a particular temperature, I still have to manually switch it between "Heat" and "Cool" mode, and this seems to be true of every thermostat (programmable or not) that ...
4
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2answers
734 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 ...
5
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1answer
645 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 ...
10
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2answers
81k views

What's the most common cause of A/C refrigerant 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 ...
5
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4answers
253 views

How can I keep a bedroom warmer in summer?

The master bedroom in my parent's house tends to be the coolest room in the house, and my father complains it's too cold. The A/C register in the ceiling does have a flow adjustment lever, but it's ...
13
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3answers
6k views

Is running ethernet cable through an air return allowed under US code?

I'm looking to wire up the second floor of my house and the cold air return provides a convenient, straight run from the office to the utility room. Is it safe and within code to run ethernet cable in ...
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4answers
909 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
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3answers
131 views

What concerns should I have installing a HVAC unit and ducts in a home that's never had it?

We're looking at a house in southern Alabama that has no central heating and air. I would like to put one in. The house was built in 1950. What should I be considering about the installation?
5
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2answers
736 views

When insulating with closed-cell Spray Foam, what ERV and HVAC resizing considerations should I bear in mind?

I am building a 2800 sqft, two-story brick home in Austin, TX. I have heard many good things about the benefits of insulating with closed-cell Spray Polyurethane Foam (ccSPF)1, and have requested ...
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0answers
156 views

Is mold growing in my ductwork? [closed]

I am currently in a battle with my landlord over what I believe to be mold growing on the fiberglass liner of the ductwork in my apartment. He is having a specialist come to test it tomorrow, and I ...
0
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2answers
6k views

Is it normal for the A/C to be dripping from top pvc that's coming from attic?

I thought I remember being told that water should drip (condensation) from the bottom pvc that comes out of the house but it should never drip from the top pvc. I thought he told me that if it ...
4
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1answer
2k views

Adding AC to forced air system

We have an old house that happens to have forced air. Unfortunately, according to an HVAC tech it looks like there aren't sufficient return vents to add a compressor to our furnace. I guess I'm ...
7
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1answer
982 views

AC issues / Insulation of vaulted ceiling

Issue: If it's hot outside, ~90F, house temperature can't get below 79F. Background: 6 year old house, vaulted ceiling with 1 ceiling fan in family room where thermostat is (also 3 large windows, ...
6
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4answers
1k views

Why aren't Geothermal heat pumps more common?

Air conditioning and heating are major energy consumers in American buildings - commercial, residential, and industrial. I have been curious for a while as to why it isn't more common to use the ...
2
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2answers
813 views

Recommended proximity of HVAC vent to return air

I have an upstairs room with an HVAC vent in the ceiling above the door. The return air is in the hallway just outside of the same door. This room also happens to be the hottest room in the house (by ...