Questions tagged [hvac]

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

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0answers
17 views

Need help with weird (?) wiring to thermostat and condensate pump

I've searched a lot and can't quite find what how to solve this one. I installed an ecobee smart thermostat, which didn't work with 5 wire connection so I switched to their PEK module with only 4 ...
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3answers
82 views

What could be the sources of humidity that build up in a house in an arid environment? Outside RH: 10%; Inside RH: 40% +

We open our window at night at the temps get down to 70F @20% RH. The temp in the house drops to 75F and the RH is 33%. We close our windows when we go to work. When mid day comes, outside, the ...
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29 views

I am installing a Honeywell Pro 2000

So, I have the green, white, blue and red wires coming in, but DO NOT have a yellow. There is a brown. I do have both regular gas heat, and AC. What terminal should the brown wire go? And should the ...
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4answers
98 views

AC air feels unnatural

I have a general question concerning air condition systems. Basically to me the air coming out of the AC unit doesn't feel natural. I've experienced different types of AC units, from small to quite ...
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1answer
31 views

Secondary C Terminal on Furnace Circuit Board?

I was trying to install an Ecobee thermostat, and there was no C wire installed. When I went to install the power extender kit, I saw the standard C wire terminal was broken out of the black plastic ...
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0answers
10 views

Lennox G51MP shutting down with Primary/secondary switch fault

I have Lennox G51MP-48c-090-06 ~14yrs old, starting up for first time this season. It is throwing error code: Primary or secondary limit switch open. Unit shows normal operation when powered up and ...
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0answers
18 views

Geothermal system that will not always cycle down at set point

I have a Geothermal HVAC system (no outside unit). Occasionally it will continue to run well past the set point and not cycle off. It may do this once in a week or once in a few weeks. If I turn the ...
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1answer
40 views

Ducted A/C system under powered

I recently replaced carpets with tiles in my apartment, and in the process generated an incredible amount of dust. All this dust was sucked into my A/C ducting, and the filters in the return were ...
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19 views

The burner on my Lennox G40uh furnace will not ignite

I have a Lennox G40 series furnace and the gas valve will not open. After it does the preliminary start up I get 27V to the gas valve, but only for about half a second. Periodically the LEDs will ...
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1answer
42 views

Where should I connect my C-wire on my old Goodman unit (GMP075-4 rev 13)

I want see if someone help me on hooking up this new Honeywell thermostat with Wifi I just purchased. I have an old ac unit and I only have 3 connections to my circuit board which does not have an ...
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0answers
60 views

No power to isolator switch

I recently moved into a repossessed flat and the electrics were a bit of a mess. Sockets, switches, etc. hanging off walls but it has since all been made safe/good by an electrician. The only thing ...
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1answer
20 views

How should I insulate garage ductwork when no gap exists between ductwork and ceiling?

I currently have uninsulated HVAC ductwork running the width of my garage. There's no gap between the ducts and the plaster ceiling above it. There's also very little clearance between the ducts and ...
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2answers
48 views

Going through condensate pumps every 2-3 years

I am about to buy my 5th condensate pump in 12 years. HE furnace or 2.5T A/C run 10-11 months out of the year here. Humidifier attached but not in use. I have a 7.5' rise, 20' horizontal span, then 8'...
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1answer
20 views

Heater tripping off outside breaker

I have a Payne AC/Heat unit outside my mobile home. When I turn the thermostat to heat, it runs and blows air for about 10 seconds and then trips the outside breaker at the meter... From the meter I ...
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2answers
36 views

Do two-stage compressors offer both two-stage heating *and* cooling?

I received a quote for a two-stage heat pump (model HCH636GKA). I have the following questions: Does a "two-stage heat pump" imply a two-stage compressor? Does a two-stage compressor guarantee two-...
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2answers
47 views

Insulating a Wall Against Unconditioned Attic Space

I'm looking for help in insulating my 1950s San Diego house. A second story was added in the 70s and a gas furnace + A/C was added about 10 years ago in the unconditioned space above the downstairs ...
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0answers
19 views

Eliminate Humidistat

I have an old Honeywell H8808 humidistat and a Pro 1 model T721 thermostat and the problem is that when the humidistat is turned down far enough to kick the system on it will come down to set ...
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0answers
30 views

Installing HVAC return in mold-infested room

We're in the process of reducting our house for a central HVAC system. We have an insulated "cold room" in the basement that had an outbreak of green mold in the past, probably from an old fridge but ...
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0answers
22 views

Furnace Blower Motor Wiring

I'm replacing a 1/3hp, 120v, 1075 rpm GE S336 S furnace blower motor with a Century model. Disregarding the capacitor and green ground wire, there is a discrepancy between the old and new. GE motor ...
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1answer
42 views

Why is my HI HEAT terminal causing blower to run non-stop?

I am trying to troubleshoot what is causing my blower to run non stop (the condenser (outside unit) comes on only when cool is required). There is no issue with cooling the house. I read through all ...
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1answer
27 views

AC Fan/blower not shutting

My AC unit is working just fine and shuts down at/below set temperature. However, the AC fan keeps running all the time even in auto mode. The only way I can shut down the AC fan is to power-down my ...
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2answers
64 views

HVAC AC Capacitor Replacement

I have a Carrier Infinity Series AC Unit (Model #: 24ANA748A0030020 or 24ANA748A00300); its capacitor needs replacement. I live in Chicago; so VAC is 120 x 2. Current Capacitor Specification: ...
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3answers
60 views

How to safely clean rust and prep on a section of HVAC ductwork before insulating

So I have a small section (about 1.5 ft) of non-insulated ductwork with some rust right above my HVAC blower/furnace in the basement. The rust seems to be caused by the water that sweats on that ...
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1answer
42 views

How to extract and then add new refrigerant oil to a home hvac system after existing oil was contaminated with humidity?

Condenser copper refrigerant lines were cut by vandals. They stayed open for several days. Before recharching with r-22, i know the repairmen will have to braze the copper lines and remove all the ...
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1answer
50 views

Furnace/HVAC issues in new build

Just had a couple of questions. I have been in new build townhouse for a month and noticed a couple of things but have been away several weeks so just dealing with it now. Some of this I am sure I am ...
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1answer
32 views

Furnace relay - old one says 18 LRA, replacement says 48 LRA - Does it matter?

forgive me if this is a newbie question. I am replacing a relay inside an electrical furnace/air handler. It is a relay model 90-293Q. The original one I have specifies it as "8 FLA, 18 LRA" but the ...
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2answers
76 views

Adding a return vent to a hot office

I have an office with a significant amount of computer equipment in it that generates quite a bit of heat and is regularly 3-12 degrees warmer than the rest of the house when I'm working in there with ...
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2answers
54 views

Heat pump not working after rain

A couple weeks ago, I had a Goodman 3 ton heat pump split system put in. At 5pm hours today, I was outside near the heat pump and noticed that it was functioning properly. At about 6pm, there was a ...
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1answer
32 views

Mold at Air Return

I have 2 HVAC units, one for upstairs and one for downstairs. When I went to change my air filter for the downstairs unit I noticed some mold in the return duct. This is a large duct that travels ...
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1answer
61 views

More wires than Nest needs

I had an old thermostat with wiring as below image: I wired Air Handler Trane (Model# TWE037E13FB2) in the attic just like it was before: Here is a wiring diagram of Air Handler: However, my Nest ...
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0answers
51 views

Replacing old thermostat and two unidentified wires

I'm replacing an old thermostat from the early 90's with a new wifi thermostat. When removing the old one, it only used R,G,Y,W wires, and the new wifi thermostat requires a C. After fully removing ...
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0answers
63 views

Why is my HVAC system not turning on the A/C compressor?

My AC stop cooling. Here's what I found. Inside blower is working, outside compressor/fan does not turn on. I manually push the contacts in the outside relay and the compressor and fan worked, used ...
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0answers
47 views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
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0answers
34 views

New Unit with Blocked Condensate Lines

A little over 30 days ago a new HVAC unit was installed at my home. Saturday night I had a buckled ceiling and a BIG problem. The installer told me both primary and secondary lines were clogged—-the ...
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4answers
69 views

Should I switch to a vertical exhaust fan to avoid 90 degree bends?

I am replacing the original kitchen exhaust fan on my 1950s house. The old one vented sideways to an immediate 90-degree bend (to 8-inch rigid ducting) and then straight up about 24~36 inches to the ...
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3answers
35 views

combining a humidifier with refrigeration cooling, what do you think?

I live in a high humidity (75%) climate. I wanted to know what happens when you combine a light humidifier with a normal AC set on "dry" mode. The AC is activity reducing humidity, which helps me "...
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2answers
56 views

How to investigate a problem with blown 50 amp HVAC fuse without power?

My AC unit has the fan working but not the condenser and I found that one of the two 50 amp fuses was bad. Unfortunately after replacing it, I saw and heard a spark and the new fuse was blown ...
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2answers
54 views

Is it OK to stop the indoor blower during heat pump defrost on split-system heat pumps?

The traditional North American split system heat pump (ignoring "dual fuel" systems for now) relies on a backup heat source to provide both makeup heat during low-temperature (below the system balance ...
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1answer
44 views

Is my HVAC system one or two transformer based?

I have read Do I have one or two 24V transformers in HVAC control circuit, but as it appears I don't have two geographically separate units for A/C and heating, believe this to be a different question....
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2answers
140 views

Storing comsumable dry goods in your car in the summer? [closed]

I live in South Florida where the summer sun has no mercy. I drive a new van and I've taken steps to keep the inside cooler during the day. I live in the van for weeks at a time and need to store ...
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3answers
43 views

Fan is turning on air conditioner but no air movement

A few weeks ago I changed the outside unit's starting capacitor and that got the fan on that unit to rotate and the air conditioning on the enclosed back porch started working. Today I came home and ...
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4answers
59 views

What parameters affect the amount of btu required to cool a single room

Background Due to the reason I lack knowledge in air conditioning I asked a company that manufactures and sells a\cs to send a consultant to advise me on which air conditioner I should use in my room....
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7answers
10k views

Why does my house heat up, even when it's cool outside?

Summary The question pretty much says it all. It's probably a ridiculously easy one to answer. It's cool outside but I know that my house is heating up because my AC kicks on periodically. I've ...
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1answer
1k views

What causes burn marks on the air handler in the attic?

What caused these burn marks? Phoenix Arizona suburb. House was construction complete about 6 months ago. The tape and insulating foam around the bigger tube was cut. I assume the AC tech that ...
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2answers
33 views

Thermostat “fan” function actually using air conditioning

A few months ago, my wife and I started sleeping with our bedroom doors closed to keep out our cat. We would wake up in the middle of the night to find our bedroom was very hot and it felt really hard ...
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3answers
63 views

I need to pressurize a room and I'm kind of at a loss as to how to do it, hoping someone out there might have some advice

I'm setting up a small packaging operation for edible products for pets. There are certain government standards we have to hit to be able to do this. The actual packaging takes place in a 420 sq ft ...
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1answer
32 views

Mini Split Condenser wall mount on wood exterior wall

We have a wood-frame house with 2x4 studs and half-inch plywood exterior walls. What is the generally accepted best practices for mounting a 80lb mini split condenser on a wall bracket to this type of ...
3
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1answer
62 views

Can I draw 240v out of this configuration?

This is how my subpanel looks like. I am looking to install a breaker for an AC unit. 20A. The only caveat is that this has to be 240V. This is a subpanel coming from the main one. There is a breaker ...
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2answers
40 views

Adjusting HVAC damper

First summer in this 2 story house and looks like air flow on the second floor is significantly weaker then on the bottom floor. Looked at the HVAC to find the dampener handle and found 1 but it is ...
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1answer
33 views

Add common wire to furnace

Trying to add common wire to furnace for smart thermostat. Looking at wiring diagram, it looks like common wire off transformer is blue, switches wire color to white (via wire cap), then back to blue (...