Questions tagged [hvac]

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

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2answers
207 views

Can I put a 20Amp breaker on a 55 amp line for an A/C unit?

I have an unused 3 wire 220V 55 amp circuit from the meter from my old A/C unit running right where I need a 20 amp 3 wire 220v, is there a way to reduce the circuit, put in a remote 20 amp breaker ...
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2answers
44 views

What goes into replacing a package unit (HVAC)?

I have an A/C, Heater package unit on the roof of my condo in Southern California. My unit works but my neighbor's just kick the bucket and it is being replaced. The estimates she got varied from $7k ...
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8answers
65k views

Better to run air conditioner fan on high or low speed?

In my apartment, I have two window air conditioning units. Both have different settings for the fan speed: one has two speed options and the other has three. Both have the design that the room ...
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1answer
32 views

Air Conditioning Thermostat Wiring

A set of three air-conditioners cool a storage building in an American sub-tropical environment. There is no heat: AC only. Cooling is signaled by switching the RED (24V) to: Yellow wire (cooling ...
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3answers
5k views

Does my furnace suck air from outside?

I've tried Googling this but the stakes are quite high and I don't want to be wrong, so I'm asking here. Wildfires are raging in California where we live, and the Air Quality is nearing the 'hazardous'...
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0answers
27 views

Opportunity to relocated HVAC system from attic to basement

Our >10-year old HVAC system (heat pump and 3-ton air handler) need to be replaced. The heat pump is need of new parts, but we were advised given the age of the entire system that it would be more ...
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0answers
36 views

Need to move my vertical HVAC return approx 3 inches away from my furnace

I installed a power humidifier to my furnace side (had to be mounted facing the face of the A-coil on the plenum per OEM) . and it's mounted in between my furnace and cold air return. The unit (...
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3answers
4k views

Smart Thermostat Keeps Losing Power

I just switched my upstairs and downstair thermostats for smart thermostats. The C wire was not connected so I opened the furnace and connected it. Both units deliver 27v to the thermostat. I read ...
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1answer
48 views

Heat-pump style AC is not putting out cool air

I live in the Northern area of the US, and I have a heat-pump style AC unit. So there is an AC unit with big fan outside my house, and there is a furnace in my attic. I bought this house 10 years ago ...
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0answers
24 views

HVAC furnance runs for awhile, stops for 2 minutes, then starts back up and continues to heat until set point reached

I have a Carrier 58GS150 system. At night it is set to 69. In the morning it is set to 72. Recently, I replaced the air filter. The system starts up fine in the morning and tries to reach 72. ...
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0answers
45 views

C Wire - Williamson Furnace/Honeywell Thermostat

I'm trying to install a new wifi thermostat, but am a little confused. I have 5 wires, but none are connected to the C in the thermostat, as seen below: Additionally, when I trace the thermostat to ...
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1answer
86 views

Why did HVAC company add a heat outlet register venting into my attic?

I recently had a brand new HVAC system installed in my attic. The furnace is natural gas. The furnace kept shutting down after 7 to 12 minutes, due to "too much air" blowing on heat sensor ...
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1answer
3k views

C wire - thermostat - not providing power

I'm replacing my old Honeywell thermostat with a new Wifi thermostat. My old/current one is battery powered and doesn't use the C wire. I found the C wire behind the plate. I connected the c wire to ...
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1answer
39 views

4yr old heat pump doesn't label 24v C wire

I'm used to the gas furnaces, and I still want to swap out this 4 year old heat pump, but it would be too expensive. I recently bought a smart thermostat to try and help with the utility bills, but it ...
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1answer
59 views

Wiring an ECM to AC power

I'm trying to wire a motor to work on 120v ac power. I accidentally bought an EC motor, because the price was so low, and cant find any sort of wire diagram for it From research, I found that all of ...
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0answers
16 views

c wire question

I have a gas fired hot water boiler with 18/2 thermostat wire running up to my regular non wifi thermostat . I want to know if I ran a single (blue ) 18 g wire from my c terminal on my new wifi ...
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2answers
4k views

Can I install a modern furnace without ductwork?

I removed an old coal furnace from my basement. The furnace did not have any duct work to speak of. There was an exhaust pipe which fed into the chimney and a duct that went into the next room, but ...
3
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1answer
539 views

Can a motorized damper be installed inside existing ductwork?

My HVAC system consists of a fan, furnace, compressor-driven AC, and evaporative cooler. The problem is that there is a large air volume used only by the evaporative cooler that is generating a lot of ...
11
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3answers
3k views

Why would an air conditioning unit specify a maximum breaker size?

A ductless mini split unit I am interested in specifies a maximum breaker size of 15 amps. Why would this be the case? The unit is going to be installed on the opposite side of the house from where ...
3
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2answers
102 views

To mitigate radon, is a “positive” basement pressure possible during balancing?

Our basement has low-moderate radon levels, fluctuating typically between 1.5 - 4. We do have a subslab mitigation pipe, but it doesn't work great. For other air quality reasons, we decided to ...
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1answer
80 views

Is my control board bad?

I have a Goodman evaporator/gas heating unit that runs the central fan motor constantly after it is powered up a couple of seconds. This happens regardless of what wires are hooked to the control ...
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0answers
24 views

HVAC auxiliary fan relay wiring help

I set up a two zone whole house dehumidifier system with 24v no/nc dampers, primary and secondary zones. the primary zone is controlled by a Aprilaire model 76 external control and the secondary zone ...
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1answer
150 views

Heating above ground pool by re-circuplating pool water through tankless, on-demand water heater

Due to covid-19 all indoor pools in my area are closed for the foreseeable future. Kids being swimmers, I purchased an Intex 15' round above ground pool and installed in it in the garage. It worked ...
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1answer
655 views

convert a onan 110v generator to 220v

My RV has roof-top air conditioning units. The generator will run 2 units. I would like to convert the RV to a mini-split system with 2 air handlers. They require 220V, and draw 25 amps; however my ...
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2answers
477 views

Need help with 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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5answers
6k 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 ...
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1answer
95 views

Swapping to Hive thermostat. 4 wire communicator has 2 wires per post

I'd previously asked if I could swap my wires from the 4 wire communicator to the larger board and was told I could. I finally found time to do it. However, as I was preparing to move the wires, I ...
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2answers
603 views

Is there some type of coating I can use to prevent condensate on my HVAC ducts?

I'm getting a lot of condensate on my HVAC ducts that run though my first floor (and HVAC blower) especially in July / August when humidity levels are outrageous (in NJ). The 1st floor space space is ...
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1answer
30 views

heat is not responding to thermostat set temp but comes on when turned off and back on with the thermostat switch

At times during the day my gas burner doesn't try to come back up to the set temperature on the upstairs or downstairs main thermostat. I'll hit the up button a couple of degrees but no change. Then ...
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1answer
26 views

Can I get away with 12" round supply and return for 2 ton?

replacing two package AC heat pumps that are 20+ years old, going to convert it to a split system with an air handler inside an insulated closet style box on the outside of the house. Ducts are in ...
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1answer
40 views

Can I use a 220v 60 amp breaker and 4/3 line for a sub panely with 2 breakers 220 1 35 amp and 1 15 amp

I have two old package heatpumps supplied by what looks like 4/3 lines each on its own breaker. 60 amp fuses. I am installing two split units the condenser requires 220 and 20 or 35 amp depending ...
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1answer
71 views

Can a single 8“ flex duct be split into a 5” flex and 7" flex?

Our house used to have a fur-down A/C unit that fed a series of rigid ducts made with duct board. We'd like to replace a vent in our bathroom (5' x 11') with a 5" flex duct. We'd like to ...
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4answers
10k 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 ...
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1answer
13 views

Two Sets of Wires on HVAC Panel

Ultimately I'm looking to use a C wire for a Nest thermostat, but upon looking at the HVAC panel I'm confused by the wiring. There's a grouping of wires going from the HVAC panel to the thermostat: ...
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2answers
37 views

24vac transformer inside furnace

I'm adding a humidifier to my furnace. The included 24vac transformer fits nicely on the inner electrical box in the upper furnace compartment. I like that it keeps everything behind the external ...
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1answer
26 views

Replacing swamp cooler pads

I have a AercoCool Pro 4800 swamp cooler roof unit and need to get new rigid pads for it. Do the pads need be specific to the brand according to the cooler's spec sheet, or can I use any pad that is ...
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0answers
18 views

Hard to Pin-Point High Temp Limit Switch Issue

I have been having an issue with my furnace for awhile now which can't seem to be solved. Had a furnace service out to review it and he spent 6 hours here trying everything. Below are the facts. ...
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1answer
903 views

Wiring a C (common) wire to a Triangle Tube Prestige Excellence 110?

Wiring noob here. Can someone give me step-by-step instructions for where and how I should attach a C (common) wire to a Triangle Tube Prestige Excellence 110 boiler for a ecobee3 thermostat? I think ...
0
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1answer
57 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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0answers
14 views

Diagnosing CH 05 (communications failure) in LG mini-split system?

I installed a mini-split system in my shop (it's the second mini-split I've put in; the first went great). Everything appears fine, except that after a few minutes, the system shuts down and the ...
1
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1answer
50 views

Can I use a plastic basin positioned near joists to compensate the lack of slope in a ceiling condense drain?

Is this a design that is acceptable? Basically I am building a small box that will collect water pumped up by the condense drain. I will put this up in the ceiling in the furnace room just between the ...
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1answer
77 views

Sound proofing a panned floor joist return run (basement apartment)

I'm building a basement rental unit in our home. We'll be living upstairs so I'm doing my best to sound separate the upper and lower units. I'm using a seperate hvac system for the basement (baseboard ...
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1answer
436 views

Sealing a closet door that has a gas fired water heater in it

Does anyone know how to make a self sealing door? There's a bedroom in my basement, and it has a door in there that allows you access into the HVAC room (which can be entered from another door in ...
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1answer
73 views

Replacing A/C thermostat

I think that my mother has a bad thermostat. When the A/C is turned on, the furnace blower works but not the outside unit. However, when I press the contact switch (outside), both the compressor and ...
2
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1answer
10k views

Goodman gas furnace limit switch opening, blower only runs with a/c

I apologize in advance for some of my incorrect terminology. My father has a 2004 Goodman GMH80904BN gas furnace with a/c. The a/c has functioned properly all summer here in Ohio, we have recently had ...
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1answer
137 views

Why doesn't my home cool down when the air conditioners run?

I have two HVAC systems (2x condenser outside, 2x evap in). I just got them repaired after they started leaking two years ago (have not used it for two years). Both AC's came with the house, and I ...
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1answer
634 views

How to improve heating/AC flow in second floor?

We moved into our house about a year ago and the second floor in my house never get enough heat in winter or cold AC in the summer. Our first floor can be a 72F deg while our upstair stays at nearly ...
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2answers
322 views

Why won't my electric furnace kick on unless the thermostat is set to 73?

I have an older, ill insulated mobile home. My house is obviously not 73 degrees, and my heater will not kick on. I set it to 73 and it finally came on, but then the furnace would not shut off. It ...
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1answer
51 views

Blower Motor Heat and Cool Control Board

I’m an electrician by trade but i have a friend who needed his blower motor replaced. The parts store sold him a motor but it only has one hot leg. The control board has a hot for cooling and a hot ...
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2answers
56 views

What type of bracket to use between furnace and evaporator coil unit?

I have a horizontal Goodman furnace and evaporator coil installed, and I want to know what kind of bracket I can use to connect the two. The installer did a bad job and used tape and mastic to ...

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