Tagged Questions

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

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2
votes
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 ...
1
vote
2answers
896 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
15k 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
341 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
162 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
232 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
512 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
946 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 ...
1
vote
1answer
4k 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 ...
3
votes
3answers
3k 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 ...
4
votes
3answers
997 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 ...
7
votes
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
votes
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 ...
3
votes
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 ...
5
votes
1answer
263 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
votes
1answer
321 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 ...
4
votes
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
votes
1answer
451 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 ...
2
votes
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
879 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
votes
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
votes
3answers
5k 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
464 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 ...
5
votes
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
votes
2answers
899 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
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
votes
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 ...
35
votes
4answers
136k 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
votes
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 ...
3
votes
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 ...
1
vote
2answers
1k 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
votes
1answer
133 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
votes
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
votes
2answers
833 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
votes
1answer
829 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
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 ...
1
vote
1answer
873 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
votes
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 ...
1
vote
4answers
598 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
806 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
103 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 ...