Questions tagged [hvac]

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

434 questions with no upvoted or accepted answers
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977 views

Can I run a C wire from Fan Relay

We've just moved into a new home with an heat only, oil, forced hot air furnace. The current thermostats are very old and we'd like to update them to something like a nest. The furnace is currently ...
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12k views

'Wait' indicated on my Honeywell RTH7400 thermostat after 1 week vacation

New Homeowner (December) and I need help troubleshooting. Everything was peachy keen until I returned from a week vacation. A/C will not cool, but fan will turn on if I take it off of auto. "Wait" is ...
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682 views

Changing Furnace to Direct-Vent, can i get rid of these pipes?

My 96% furnace uses a PVC pipe to exhaust the combustion gases to the outside. The intake is currently taken in through a inlet similar to the exhaust on the left side of the furnace. It does not ...
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202 views

Can I usefully control an electric baseboard heater in 1 room with the same thermostat as my central heat?

My house has a gas furnace and heat pump (and AC). Unfortunately, one bedroom does not have air ducts hooked up. Is there a way I could install a baseboard heater in that bedroom and have it ...
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882 views

Replaced HVAC Transformer, still have no output voltage

My HVAC stopped working, no matter what state the thermostat is in there is no fan, no compressor, no heat, etc. Using a multimeter, I found that the output voltage on the transformer was 0V. ...
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52 views

Studio HVAC Solution

I have an interesting situation where I am in a studio that is approximately 300 sq. ft., and should require ~9,000 BTU/h (3/4 ton) heating/cooling capacity. There are three rooms--A bedroom (~11x8), ...
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1answer
1k views

C wire and smart thermostat

I'd like to install an ecobee3 thermostat, but I'm not entirely sure about my wiring. The current thermostat seems to only have a W and RC wire coming into it. There is also what appears to be a blue ...
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1answer
777 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 ...
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79 views

What is this device connected to my HVAC unit?

I have this device connected to my HVAC unit in my apartment. I only have it in two of my rooms. In one of the other rooms I do not have this unit and was able to install an ecobee seamlessly. However,...
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55 views

ECM motor in air handler not reaching full speed

I replaced the motor back in this thread at the height of the summer heat: old question The old motor was fine as I opened it up and a bug got fried inside and caused a short. I ended up with a ...
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57 views

Risks of Unplugging Lennox HealthClimate Unit

I bought a home with a space age lookin' Lennox HVAC. Instead of using a basic paper air filter like you can get at a local department store, the unit has a big paper air filter and a photocatalysis ...
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347 views

Installing new thermostat without a C wire. Can I use my heater/R wire instead? Random 13V as well

I'm installing a thermostat, but I don't appear to have a C wire. My old thermostat had R/RH,Y,G,and W. It's an AC system that was setup before I got here. The actual AC unit is a long way away and ...
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46 views

Reverse motor direction not working (just stops)

So I successfully purchased and installed an Mars 10204 motor and installed it in my condenser unit outside (the previous GE motor died a horrible death after years of service). Only problem is it is ...
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146 views

Replacing Capacitors in HVAC Condensor

The fan on the outside condensor of my HVAC system stopped spinning. If I give it a push it starts up. My understanding is that this typically is just the capacitor going bad and is a relatively ...
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647 views

Adding a C wire

I know this question has been asked multiple times and I'm going to try some of the methods I have read in other threads but wanted to ask this question since I didn't see anyone else's wired the way ...
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0answers
34 views

What caused this motor to short?

These pics are from my ECM motor in my air handler. I knew the motor was my problem when it failed a phase-resistance test between the windings. The new motor passed the test and works great. I ...
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1answer
998 views

Honeywell VR8300A3500 Single Stage Heat Gas Valve to Ecobee3 with C wire

Hey everyone have a quick question regarding a honeywell VR8300A3500 Single Stage Heat Gas Valve and the introduction of a Ecobee3 wifi enabled thermostat with a "C" wire. just want to make sure i am ...
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54 views

Clean filters and dusty house

I have good airflow and a very dusty house and large dust balls. I have used all kinds of filters including the pleated. When filters are checked in 3-6 months they are as clean as the day they were ...
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0answers
2k views

AC capacitor testing with multimeter

When running through my check list to start the AC for the spring/summer I noticed the outdoor fan was not running, hence no cooling. I'm using a basic digital multimeter to test a capacitor with the ...
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1k views

Thermostat will not power on with C wire, but it has voltage

I recently purchased a Honeywell wifi thermostat and tried to hook it up as a replacement for an existing battery powered unit. I have a typical forced air HVAC setup with gas furnace (no heat pump), ...
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2answers
4k views

Why might a thermostat refuse to switch from Heat mode to Cool mode?

I have this Honeywell RTHL2410C programmable thermostat and typical Florida electric AC system. Starting this Spring, it has started behaving strangely when switching from Heat to Cool mode. The ...
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416 views

time delay adjustment on Rheem elect furnace

Upon a call for heat the blower motor starts too soon resulting in cool to cold air coming out of the ceiling registers until heat strips start heating up.Wires coming from thermostat connect to ...
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1answer
812 views

Need help adding a C wire for a wifi thermostat

With the increasing popularity of wifi thermostats I know this question has been asked many times, however I'll ask it again fr my specific situation. How do I add a "C" wire to my existing air ...
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995 views

HVAC - hot air flowing on both zones when only 1 zone should be on

I have 2-zone forced air heating, with separate thermostats for each zone. Normally, if the thermostat in zone 1 triggers the system to go on, the heat will only blow through the vents in zone 1. ...
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2answers
266 views

Replace insulation in a Trane HVAC? (TWE030C140B0)

I found a little mold on the foil covering the insulation in my TWE030C140B0 air handler/ AC/Heater. I am 95% sure I have the moisture problem resolved and now I need to replace the insulation. Does ...
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0answers
110 views

Temporary Remove Flex Duct

I am about to replace a load bearing wall in unfinished basement. There is flexible duct attached to plenum that I need to temporarily move out in order to put the beams in. Do i just need to cut ...
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0answers
72 views

Is there a “bending rigidity index” of some sort for semi-rigid aluminum ducts?

Some semi-rigid aluminum ducts bend easily and others do not. I want to purchase semi-rigid aluminum ducts online of a specific bending rigidity/stiffness that minimizes sagging but can be easily ...
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48 views

How to connect 4 fan coils with one wall control thermostat?

I have 4 fan coils (Sabiana sk-22)and I want to connect them with one wall control thermostat. How can I do?
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0answers
35 views

Thermostat and thermostat system for small business with several units and tenants

Am the facilities guy in a small church and pre-school. There are 8 heat pump units through out the church/schoool. Each has a stand-alone thermostat and they are all different. I would like to get ...
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2k views

A/C still blows when unit is off.

Our A/C is turned off but we still get cold air coming out of the vent diffusers. This is from our downstairs unit. Is that a problem?
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302 views

Can I remove HVAC pipes after exposing the ceiling?

I recently removed the drywall ceiling from my basement and have two related questions about removing the HVAC ducts/pipes. Pictures attached here: http://imgur.com/a/qep4w 1. Is it OK to remove the ...
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154 views

Testing the exhaust of a natural gas furnace?

I recently had maintenance performed on my natural gas forced-air furnace. During this maintenance, the technician went outside and used an electronic handheld device with a wire-attached probe to ...
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314 views

How can I install a furnace register in a kitchen-cabinet toe kick?

I'm planning to install new kitchen cabinets. I'll be covering up the kitchen's existing sidewall diffuser with new cabinets, so I'd like to relocate it to a new register in the toe kick of the sink ...
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2answers
15k views

why does my heat pump wiring diagram show 7 wires going to the thermostat but the thermostat only says it needs 5?

Here is a link to the wiring diagram for my heat pump. The thermostat that I am planning on buying has the following terminals C, G, Y, O/B, RC, R, Aux, E, and L. The instructions say to jump the RC ...
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0answers
2k views

How can I tell if my bathroom ceiling vent is working properly?

Seems to take the vent forever to clear shower vapor from room. I purchased a vent that had a good rating. It is vented to the outside. How do I know if it is working properly and actually venting to ...
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0answers
97 views

How do I troubleshoot my central A/C?

It's 79 outside right now. It's been running for hours and it's remaining 79 inside. I'm in a brand new 2 story home in Monroe, OH. It has rained a lot recently but I just feel like it should be ...
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0answers
120 views

Why doesn't my A/C get power when using the alternate C-wire thermostat hook-up method?

I changed my old Honeywell thermostat for a new Honeywell WiFi thermostat. I installed it just as the directions stated. I used the alternate C-wire method as the old unit did not have one. ...
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0answers
11k views

How do I size a wall sleeve for a through-the-wall air conditioner?

We are shopping for a through-the-wall air conditioner. We do not currently have a hole in the wall with a sleeve in it. We are trying to figure out what sleeve to buy. The air conditioner we like ...
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0answers
8k views

What's causing my draft inducer to stay on?

I have a new, 3-year old, high-efficiency, gas furnace in my home. I recently realized that my draft inducer, which normally kicks on before the burners and before the main blower, is not stopping. ...
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1answer
2k views

How can I properly drain heatpump condensate?

I have a heat pump in the attic That drains to the ground outside two floors below. I naively added a hose fitting so I could redirect the water where I wanted it, slightly up hill. This created a ...
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1answer
2k views

Fan works for heating, but not for AC, where to start?

Our new place has a working AC (meaning that the physical box outside spins and can produce cold air) and a working fan (meaning that the fan spins and is able to put air out to the vents in the house)...
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1answer
2k views

How to connect Nest in Europe

I found a question regarding the Nest thermostat here. But that is only a question "Will it work?". Thanks to that I know it WILL, the problem is...HOW. I know the wire naming conventions are ...
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23 views

Ventilating a flat roof

My ensuite bathroom has a major humidity problem. I took the fan out (it's one of those combo heat lamp + light + fan units) expecting the fan to be broken, but found another problem - it's just ...
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27 views

Nest thermostat + SIMPLE dual transformer setup. What is wrong?

I have a a VERY SIMPLE dual transformer system (Rh is the heating transformer and Rc is cooling transformer) for heat all I need is (Rh + W1) for AC all I need is (Rc + Y1) With this dead simple ...
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23 views

How to identify Direct Return vs Reverse Return Pipe

Is there an easy way to tell if a hydronic heating system has direct return pipe or reverse return pipe?
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15 views

HRV Supply/Blower making a terrible sound

Here is a video (with sound): https://streamable.com/w8tgqk (You have to go about 0:20 in to hear the sound). I got unlucky during recording and the sound was more intermittent, but normally it's loud ...
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12 views

Pilot light issue

Thermocouple has been changed but pilot still wont stay lit. Is it gas controller?nSo what now? I may also have a cracked heat exchanger but that would seem unrelated. A small amount ofwater ...
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1answer
37 views

What’s asbestos look like on heating vents?

I’m repainting my heating register vents and noticed something on the ductwork I didn’t see before. Pics attached. Judging from a google search, it looks like the section of ductwork that connects to ...
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25 views

How to calculate temperature rise rate for hydronic water tank

The engineering to figure this out is beyond me! I have a freshwater hot water tank that holds 30 liters of water. It is heated by hot water (coolant) running through an internal pipe (the heat ...
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1answer
108 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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