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

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4
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2answers
822 views

ductless AC split systems?

Does anyone have the ductless split AC systems offered by Mitsubishi, etc.? Is installing them a DIY job? Can you share your comments about them, in general? Edit: Inspired by DA01 comment, I'd ...
4
votes
1answer
2k 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 ...
4
votes
1answer
617 views

How can I determine if my HVAC system has features which are not currently wired to my thermostat?

I recently upgraded to a Nest Thermostat. This new thermostat supports many more terminals and features than my previous thermostat. My old thermostat had the basic terminals; G,R,C,Y, and W. I am ...
4
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7answers
56k views

Should I insulate air conditioner coolant pipes?

I recently replaced some rotted insulation on the coolant pipe that runs out of my AC unit and into the evaporator in my house. When cleaning inside the actual AC unit itself I noticed that the ...
4
votes
1answer
2k views

Why won't the fan run independently of the air conditioner?

I have central air and heat, with a Nest thermostat. My system has Y, G, R, C and W wires coming out of it: which are wired into my Nest like so: In between, there is a splice where the C wire is ...
4
votes
1answer
3k 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 ...
4
votes
1answer
11k views

How should I wire this White-Rodgers fan and limit control? What about the thermostat?

I have a wood-burning stove, that is used as an auxiliary heat source in the house. There's a regular electric furnace, and adjacent to it is the stove. The warm air duct (out) from the stove ...
4
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2answers
140 views

Dust reduction and removal?

I have a room with west facing windows (I dont think the direction bears any importance to this question), but for some reason this room seems to accumulate dust on surfaces a lot faster than other ...
4
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5answers
18k views

Why would my Goodman gas furnace start but not stay on for more than 2-3 minutes?

I've got a problem with my 15 year old Goodman furnace. It starts w/o problem, inductor begins working, hot surface ignitor lights up and ignites the gas. Then the main blower starts working and the ...
4
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3answers
6k views

How effective is a heat pump for AC and a heat pump/furnace for heating in New England?

We currently have a central AC unit and oil furnace. The AC is broken and the furnace is old, so we are thinking of replacing both sometime in the next year. We are considering replacing the AC with ...
4
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3answers
1k 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 ...
4
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1answer
1k 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 ...
4
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2answers
269 views

How to repair buckled duct work inside wall?

Update I think the duct is actually fine. The duct connects to a register that is shared by two rooms. When heating, one room is gets hot, while the other is cool (not too cold). I think the problem ...
4
votes
1answer
307 views

Is it possible to install a whole house humidifier away from the furnace?

My building is essentially a single extremely large room. It's a 25'W x 45'L x 20' H concrete box, with an open mezzanine over the back 1/3 of the box. The HVAC system is gas-fired forced air, ...
4
votes
1answer
1k views

Adding vents to duct?

My house has forced air HVAC. When I finished the basement, I used a closed cell foam insulation that worked very well. The basement will get only 8 degrees cooler than the first floor during a time ...
4
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4answers
2k views

Can I reduce static pressure in one room by adding a vent to an adjoining room?

Our return vent for our hvac is right outside the master bedroom. The master bedroom gets very little airflow with the door shut. It was recommended that we add secondary return duct in the master ...
4
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2answers
1k views

How well do whole house humidifiers work?

We are moving to an area where it gets cold and snows in the winter. We come from a desert area where it is never very cold except for the dead of winter, and where we use the heater very seldom. We ...
4
votes
1answer
4k 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, ...
4
votes
1answer
773 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
2answers
1k 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 ...
4
votes
3answers
6k 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 ...
4
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0answers
166 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.
3
votes
5answers
35k views

How much less power does a three-phase air conditioning unit use than a one phase 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 ...
3
votes
6answers
1k views

Air Conditioner Can't Keep up

We just rented a condo and our A/C cannot keep up so it will run almost constantly. It can't even keep the temperature constant, it will creep up into the 80s even while running. I measured the ...
3
votes
4answers
612 views

Air conditioning on a shoestring budget

Without purchasing expensive air-con units, or solar panels - and the associated moutings and electrical paraphernalia, is it possible to create a temperature difference of 10-20 °C using materials ...
3
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5answers
2k views

How can I vent a portable air conditioner when there's no window?

My shop does not have central air and does not have operable windows. There is a steel door in the back and cinderblock walls. My landlord is against me cutting a venting hole in either the steel ...
3
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3answers
134 views

Was this furnace installed properly?

I am looking to answer the following: Was this job done properly, and if not, then how really bad it is? And should I hire this contractor again ? Product: Ruud RGTM10ERBJS 100K BTU 95% ...
3
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3answers
3k views

How can I heat up my apartment to kill bedbugs in Southeast Asia?

I have a bedbug problem in my apartment and I want to fix it myself with heat. (I do not want chemicals sprayed around.) Apparently, getting a room to 140 degrees for two hours is sufficient to kill ...
3
votes
2answers
9k views

Why does my window air conditioner cool but not dehumidify?

I have a brand-new 5000 BTU Frigidaire window air conditioner, and it seems to work fine except that it doesn't reduce the humidity in the room. I turned it on last night, and the temperature was 81 ...
3
votes
2answers
443 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
5k 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 ...
3
votes
2answers
7k 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 ...
3
votes
2answers
6k 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 ...
3
votes
2answers
1k 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 ...
3
votes
2answers
105 views

Continued Excessive dust in home air

I'm having minor breathing issues and suspect the home air quality, which seems to be excessively full of particles/dust. The air quality is visually noticeable daily, regardless of basic ...
3
votes
2answers
19k views

Controlling separate heat and AC devices from a single thermostat

I have hydronic radiator heat powered by a gas furnace situated in one mechanical room of my house and a currently being installed central AC whose air handler is situated in another mechanical room ...
3
votes
1answer
6k 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
3answers
81 views

Duct Cleaning: Is Duct Sealer Necessary, Non-Toxic?

A professional contractor is cleaning AC Ducts, and after he scrubs the ducts, he wants to apply an acrylic duct sealer and de-odorizer. The container of the duct sealer has minimal lableing and does ...
3
votes
1answer
216 views

Should I be worried if my A/C ran with the cover on?

My wife accidentally switched on the "cool " mode and the a/c was activated, however the cover was still on the unit outside. Ran like this for about 2 hours. I noticed it and turned it off and went ...
3
votes
2answers
2k views

Can I attach a HEPA filter to the HVAC outlet?

I am currently living in China and want to improve the indoor air-quality. We have a Hitachi R410A HVAC. All the room in the house are controlled separately. Just to make it clear up front, I am not a ...
3
votes
3answers
10k views

How can I cut a cinder block wall to run large round duct through it?

When an addition was put onto the house that I own, the previous owner just ran the duct work into the crawl space through an old basement window. I want to re-route the duct work by actually cutting ...
3
votes
2answers
793 views

What is this name of this vent attachment next to my furnace?

What is the name of this silver vent attachment thing at the bottom of the picture? It is attached to the side of our gas furnace. The black part is an insulated air duct which goes to a vent ...
3
votes
1answer
723 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 ...
3
votes
1answer
398 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
4answers
4k 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 ...
3
votes
1answer
143 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 ...
3
votes
1answer
221 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?
3
votes
2answers
138 views

How to address loud cold air return

The cold air return on my forced air furnace is too loud. While it is is tolerable, there is a noticeable sound of rushing air when the furnace is running (not a whistling sound, just a blowing ...
3
votes
2answers
1k views

Why “extra” power disconnect for small HVAC unit?

I am in the throes of learning enough to do a DIY install of a small heat pump package unit. The installation manual calls for (and suggests that NEC requires) a "fused disconnect" inline with the ...
3
votes
3answers
9k views

What could cause a flame sensor to stop working so frequently?

Over a year ago after a month in our new house, we came back one evening to a cold home and after some googling, I found out that the flame sensor was dirty and the furnace was starting the flame and ...