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

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2
votes
1answer
3k 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
424 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
5k 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
5k 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 ...
1
vote
1answer
188 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
276 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?
4
votes
1answer
769 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
1k 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
4k 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 ...
2
votes
1answer
145 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
140 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 ...
7
votes
2answers
38k 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 ...
5
votes
1answer
897 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
340 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
634 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 ...
3
votes
2answers
2k 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 ...
3
votes
2answers
4k 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
1k 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
4k 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
1k 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
votes
2answers
956 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
119 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
917 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
votes
4answers
291 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 ...
5
votes
2answers
903 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 ...
2
votes
0answers
164 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
votes
2answers
10k 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
votes
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 ...
11
votes
5answers
12k views

How can I calculate how large an airconditioner my house needs?

I know there are a lot of possible factors that go into determining the size of the air-conditioning system a house needs. Is there a standard way of calculating what is needed, or do A/C companies ...
7
votes
1answer
2k 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, ...
2
votes
1answer
5k views

Why is there water dripping from my ceiling AC vents?

I have a one story house with hot water heat. The house also has forced air AC ducts running from the attached garage, in the attic, down into the living room, bedrooms, and kitchen. At certain times ...
1
vote
1answer
841 views

Installing a duct fan

For a room in the basement we connected a ceiling register to an existing duct. It is not very strong, but I found this product that might make it a little more powerful: Does anybody know how ...
2
votes
1answer
130 views

A/C Emergency Cut-off Cleaning and Maintenance

I found my thermostat not working. After googling for a solution, I found that I may need to check my emergency cut-off. I know of a pipe that if tripped will turn-off the A/C, so I took the pipe ...
2
votes
1answer
5k views

Air deflectors on floor registers and cooling efficiency

I was once told by an HVAC technician to avoid using air deflectors on floor registers during the summer. The reason was that the last thing you want to do is to direct the heavier, colder air ...
3
votes
1answer
215 views

Improve AC flow to secondary ducts

I have an AC which has 3 ducts coming out of it. Only one duct gets flow - I'm guessing the AC fan blows right into it. What can I do to improve the flow?
5
votes
2answers
6k views

HVAC vents - does wall or ceiling mount matter?

I'm going to add some crown moulding to some bedrooms. I've got HVAC vents mounted near the top of the wall and the moulding will cover part of the vent. I want to move the vents out of the way. I ...
2
votes
1answer
135 views

Help me choose AC model

I need air conditioning (no heat; I've got hot water radiators) for the main floor of my house (around 1000 ft2). I was offered the following models (mostly Carrier) (ordered by price, descending): ...
1
vote
1answer
584 views

Furnace Airflow

I have central air. When the furnace comes on, we can feel air coming out of the registers for a few minutes, then the airflow stops. If we turn it off for a few hours, we can turn it on again and get ...
4
votes
2answers
116 views

DIYer to skilled tradesperson

What is the process a DIYer has to go through to become a skilled tradesperson? Are the only options apprenticeships, or are there other paths to follow to learn a trade/become licensed? What type ...
2
votes
0answers
620 views

What are good Relative Humidity and Temperature settings on an MHRV and are the settings related?

I need to configure the threshold Relative Humidity and Temperature settings on an whole house MHRV system. The way the system works is that if the RH threshold is exceeded the system increases the ...
1
vote
2answers
6k views

How do I connect a dryer to a dryer vent?

I just moved my dryer (gas) a couple feet to a better location in the basement. It is actually now closer to the existing dryer vent to the outside of the house. The previous owner has it connected ...
2
votes
1answer
3k views

How do I fix a condensate drain line that froze in my split electric system with heat pump?

I have a split electric system with a heat pump. It looks like my condensate drain line is frozen. I switched to supplemental heat which does not use the heat pump. Is this enough for now? Our ...
2
votes
2answers
4k views

How can I tell what kind of heating system I have?

Seems like a simple question, but I've had a very hard time finding a definitive answer to this. I went to the hardware store to buy a replacement for a faulty thermostat and when I arrived and ...
4
votes
3answers
125 views

Geothermal Resources

I am very interested in learning more about Geothermal solutions for my house. What are the best resources for learning about and planning a Geothermal systems for a residential house? Also, does ...
5
votes
2answers
8k views

Is it OK to have heating registers and returns near the ceiling?

I've got a question about a new house - a friend of my mother's is buying a new place and when she did a walkthrough (before the drywall was up), she noticed that all the heating registers and returns ...
2
votes
1answer
263 views

HVAC electric thermostat panel “goes dead” and then live again all the time

I have this digital thermostat controlling my heater (gas). When I turn it on to lets say 66 deg, and the house is at 60, the HVAC will start working of course. Problem: After few minutes, the ...
7
votes
2answers
1k views

Is there any legitimate reason to have a direct vent between utility room and attic?

I've been doing some sealing and insulating in my attic, and discovered a purpose built vent directly from the utility room into the attic space. See most of these photos The house is in a ...
3
votes
3answers
21k views

Why is my furnace blowing cold air?

My HEIL 7000 natural gas furnace has stopped working what are the most likely causes, and how to verify faulty parts? Normal operation routine Thermostat sends "need heat" signal. Exhaust blower ...
4
votes
1answer
1k views

What's wrong with my thermostat (fan / limit control)?

I previously asked about wiring the White-Rodgers fan/limit control on my wood stove. It's now wired and the wood stove is fired up. I ran the fan wires to the fan (hot) and I capped the limit ...
5
votes
2answers
6k views

How do I install a wood stove as an auxiliary heat source?

I have a house with a forced air electric furnace. We've also got a wood-burning stove adjacent to the furnace. I didn't have it installed, and I want to understand if it's been done properly, and ...