Questions tagged [hvac]

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

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1answer
29 views

HVAC Issue With Compressor

Every time the compressor tries to come on it pops the breaker. A friend who has worked in AC says its because the compressor is going bad. Is this true?
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1answer
41 views

My HVAC A/C is freezing after sundown every day

I recently replaced the capacitor on my external A/C unit. After replacement it started back up and was working fine for day or two but for the last 4 days it has been freezing up every single night ...
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4answers
768 views

Quickest way to circulate outside air thru house?

All but one major room is part of a single path through home, from a window on one end to a window on the other. In the evening I want to bring in cooler outside air as efficiently as possible. If ...
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2answers
51 views

Safe wiring of a window AC unit

I have a window AC unit rated at 115V 6.8 amps. If I wanted to plug the AC into a wall outlet, how do I determine if the wiring in the wall can safely handle the current. The wall outlet is a 3 prong ...
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2answers
26 views

how to add c wire to heat pump ac unit (only have wires with nuts)

I can’t figure out which is the C wire or how to make a C wire and how to connect it to my ecobee 3lite Power extender kit. My old thermostat has wires G,Y,RH, W/E, and O/B plugged in. No "C"...
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0answers
41 views

HVAC is heating when thermostat is off

I seem to have a problem with my thermostat. I have tested the wiring of my HVAC system by wire nutting the the power (R, red wire) to the AC (Y, black wire), heat (W, white wire), and fan (G, green ...
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2answers
49 views

Is it OK to underpower a run capacitor?

Have to replace a 55uf MFD 440 Volt VAC (model 97F9042). Is it OK to, at least temporarily, replace it with a 45uf 440V one (model ITAN PRO TRCF45)? (Some specific details of my situation. It's not ...
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1answer
86 views

Is this wiring dangerous? Smart Thermostat C-wire AC adapter twisted together

Is this wiring scenario dangerous? Is it likely produce sparks or damage my HVAC system? Please read the description and see the image below. Description I didn't have a C-wire for my Emerson Sensi ...
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0answers
32 views

Why is the combustion chamber on my furnace vibrating and humming when the air conditioner is on?

I replaced the blower motor, blower wheel (squirrel cage), and run capacitor in my Goodman GMS80904BNBB furnace (1994 model I believe) because it showed signs of bearing and capacitor failure. First ...
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0answers
21 views

Upgrading to wifi thermostat

I have a 24v power supply attached to y and c on furnace terminal block with with regular y,w,r,g and what looks like a c wire to ac coming from inside furnace. I have a wire on y,w,g and 2 on r at ...
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0answers
29 views

Ecobee3 Wiring With Heat Pump

I have an eEcobee3 I've been trying to get working with my HVAC. The HVAC is a heat pump, with the air handler in the attic. The current thermostat is a RiteTemp 6025. It's currently wired up at ...
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1answer
94 views

Where to connect C wire if no C terminal

Hi wanting to connect Nest and want to install a C wire. HVAC only appears to have G,W,R so not sure where to connect C.
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1answer
61 views

Should whole house humidifier leak cold air in the summer?

I've recently been learning a lot about sealing our HVAC ducts to improve system efficiency. On my mission to seal every accessible leak, I noticed my air conditioning/furnace cabinet joints were ...
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2answers
64 views

Electronic air cleaner vs pleated filters

I'm interested in increasing the air flow of my AC system and would like to compare electronic air cleaners (like the Honeywell F300E) to a pleated air filters (I have a 4-inch thick MERV 8 filter). ...
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4answers
2k views

Is it normal for air to be leaking from this part of the HVAC?

First time living in a house. While I was cleaning (AC was also running) I noticed that somewhat cold air leaks from the circled part of the furnace on either sides. Not sure if this this information ...
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2answers
115 views

Repurpose unused 50 amp hot tub panel for 30 amp hvac?

I have a sub panel that was from when the previous owners had a hot tub. I'm currently needing a 30 amp circuit for a mini split system and was wondering if I could just swap this 50 amp breaker and ...
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0answers
12 views

AC air handler turning off when compressor comes on

Trane air handler blower works fine in manual mode with heat/cool setting off. When switched to cool position, compressor comes on but blower turns off.
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2answers
43 views

Dual HVAC System with Dual UV lights - looking to power UV lights when HVAC runs

So I have (2) HVAC systems in the attic (2) UV Lights in the attic ducts downstream of the blower(s) (powered by a standalone 120v outlet) I would like to power the UV lights when the HVAC / blower is ...
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0answers
21 views

Does anything need to be done before using a central Air Conditioner that was installed in winter?

I bought a new construction townhouse during this past winter. I was told the central air conditioner had been installed but not tested due to the cold weather. The AC unit is for the entire home ...
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2answers
98 views

Are BTU Calcs reliable — should I oversize my system?

I had 4 HVAC contractors out to quote me a new AC system today. All of them quoted me for a 2.5 ton, considering that my house is 1000 sqft in florida, concrete slab, with a flat roof. They all said ...
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1answer
238 views

Wiring for 2-stage thermostat and 2-stage furnace with single stage cooling

I got my furnace and A/C unit replaced last summer. The new furnace has 2-stage heating, the A/C unit is single stage. The installers put in a single stage thermostat, so as far as I could tell it was ...
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1answer
40 views

Should I have the return line replaced when installing a new heat pump?

I have a 2000 sqft. house and need to replace a 4-ton R-22 system that uses a 1-1/8" return and has a short line run with the condenser 8 feet lower than the evaporator. I have received quotes ...
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1answer
59 views

Evaporator Coil Cold, but Not Ice Cold

My temperature difference between my supplies and returns is only around 5 degrees F. I opened up my air handler to see if the evaporator coil was dirty, and it was clean -- but running the outside ...
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0answers
21 views

Programmable Thermostat wiring Question

Existing thermostat is a Honeywell and has a separate connections for Aux (white wire) and E (Emergency black wire) The proposed Honeywell T'stat only has a single terminal labeled "Aux E". ...
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2answers
149 views

Is it possible to recharge a dehumidifier

I have an old Santa Fe dehumidifier capable of removing 110 pints of water per day. It has recently stopped working and the company diagnosed it over the phone as being low on R22. But they wouldn't ...
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0answers
7 views

Can a High Pressure lockout be caused by a bad unit or problems with heat rejection system?

I have a couple of Trane Axiom High Efficiency Console Water Source Heat Pumps which stop working with what seems to be a high pressure lockout. i.e. the compressor comes on, runs for a few seconds, ...
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1answer
38 views

Suction pipe insulation

I’m a new home owner. I noticed that insulation on my suction pipe was cracking. I wasn’t sure what insulation to use rubber or foam. I decided to use rubber, was I wrong?
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0answers
28 views

Replacing Central air with a Split system

I'm trying to replace two central Air conditioners (one per each floor. 2-3 ton each) in my home and I'm not sure if I should go with Ductless (because of a much lower cost) or pay higher and replace ...
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1answer
38 views

16-year old Trane central AC one package unit is not cooling well?

My central AC is a 16-year old Trane one package unit on the roof top. However, it is not cooling very well. I brought contractors in and it seems that R22 freon is leaking. However, every contractor ...
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3answers
103 views

Should my AC condenser and evaporator be the same size?

It's difficult to find a consistent straight answer on this. I asked earlier today on Reddit, and was told "It’s common to upsize the indoor (evaporator) coil to get greater efficiency". When I ...
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0answers
33 views

Closet HVAC unit was replaced with a bigger unit that sticks out into room and now door cannot be put back on

This unit was replaced in a tiny efficiency apartment and the utility closet sits next to the fridge. The closet HAD a door on it before that tempered the sound of the unit somewhat, and also looked ...
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1answer
27 views

Vacumn pump HVAC

I am going to run a 3CFM vacuum pump on my 3 ton condenser for the first time following this guide here https://www.wikihow.com/Use-a-Vacuum-Pump My questions: 1) Should I only vacuum pump my ...
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0answers
29 views

Are there any physics problems with immersing freezer coils in water?

Given a small refrigerator / freezer (dorm fridge), would there be any reason why immersing the freezer coil in water would reduce or eliminate the ability of the system to remove heat? I took a dorm ...
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1answer
78 views

what are pros and cons of an air handler located in cooled space?

The air handler unit on my central air conditioning system in Florida is located in a closet that opens to the attic. The air handler is exposed to the attic temperatures (hot) which seems counter ...
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1answer
31 views

Insulation inside AC unit has mold and falling apart

I noticed the exterior on my AC units has small black circles and I assume it is mold. A few days ago the drain was plugged and the condensation all backed up inside the unit. I had the drain fixed ...
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1answer
35 views

Simple two wire connection to a programmable Honeywell RTH6360 themostat. Have a 'C' wire in the 18/5. Do I still need batteries?

I'm assuming after reading the owner's manual that the batteries are required. I purchased this 80 dollar thermostat at a garage sale for 5 dollars in an unopened box. So i thought it might be good ...
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1answer
97 views

Flex-duct as a Trunk?

From my A/C supply plenum, I will have a trunk (approx 20ft straight run) with 3 branches coming off (each about 2 ft runs). This 20ft straight run would be perfect for a large flexible duct, and ...
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1answer
54 views

Can a twist tie be used as a jumper for HVAC?

I just moved into a new house and I'm putting in a new thermostat. The old one had a little jumper wire between RC and RH, but my new thermostat has these two terminals spaced a few inches apart. ...
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2answers
202 views

Nest thermostat causing condenser unit contactor to chatter when NOT calling for cooling

I have dual transformers, separate heating and AC. I've recently installed a nest learning thermostat (3rd gen). This is my wiring. The c wire comes from the the transformer on the AC side (pairs ...
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1answer
46 views

HVAC blows fuse when cooling kicks on

I have Rheem HVAC system that is about 12-4 years old (its an R22 unit). Today it started blowing the fuse on the board when cooling kicks on. The tstat shows a message that says power failure, then ...
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1answer
79 views

High Efficiency Furnace vented through the roof. How screwed am I?

I'm investigating installing a central air system and in doing so it was brought to my attention that my high efficiency furnace may not be installed properly. I'm in a narrow semi without much ...
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1answer
61 views

Dual hose portable AC unit creating negative air pressure

I bought a dual hose unit because it's supposed to not create negative air pressure in the room, but I can definitely feel the air resistance when I go to close the door to the room it is in. When the ...
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2answers
56 views

intermittent compressor on elderly dual-fuel heat pump

I have a 23 year-old dual-fuel 2.5-ton heat pump; it is a split system, air handler and furnace in the crawlspace, compressor outside. I use it very little in the winter, mostly heating with wood; I ...
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1answer
31 views

Furnace Displays Heat Pump mode when AC is running

I have a new Trane S9X2 furnace I purchased this winter. I want to make sure that everything is setup correctly now in the cooling season. I noticed that the furnace displays "HP1" when the AC is ...
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0answers
13 views

Connect two LP-GAS High-Eff +95% Furnaces to one LP Tank

Connect two LP-GAS High-Eff +95% Furnaces to one LP Tank will reduce supplier refill to one location on House. Furnaces 100K BTU and 60K BTU. To reduce refill to one location (currently two tanks on ...
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2answers
169 views

What's the difference between commercial and residential tankless water heaters?

I'm trying to figure out the difference between two tankless water heaters, produced by the same manufacturer, one a "Commercial" and another a "Residential". The commercial one is allowed to be used ...
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1answer
45 views

Central AC Is not Cold

My AC will turn on but will not blow out cold. I'm rebuilding the whole system, ductwork and all. I've shorted the thermostat's red (power), yellow (a/c compressor), and green (fan) wires together. ...
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0answers
62 views

Was the condensate pump in my air conditioner unit wired incorrectly?

My condensate pump stopped working - I noticed because there was a lot of water coming out of the condensed drain. I bought one brand new but when I disconnected the old one, I realized that the ...
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0answers
140 views

Rewiring for Nest Thermostat - Current ABCD Configuration Carrier

So I would like to use a Nest thermostat on my carrier system. I have the ABCD wiring configuration from current thermostat to the board on the furnace. On the attached image, you'll see three brown ...
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2answers
110 views

Minimum length of mini-split AC line

I was considering buying a cheap mini-split AC unit to cool a small room (10ftx10ft) over the summer now that we spend more time working from home. There are several units on the market. However I'd ...

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