Questions tagged [hvac]

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

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37 views

Installing Nest Thermostat. C Wire not hooked up inside furnace

Good morning. I am looking to hook up a Nest 3rd Gen thermostat that I purchased. I noticed I had a C wire upon pulling the old thermostat. Problem is it is not connected inside of the furnace. I have ...
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2answers
26 views

Thinnest screed over the water heating floor

I installed a water heating floor system with 17 mm pipes and studded panels. This is how a studded panel with a pipe looks like: It has 52 mm height (the polystyrene has 30 mm). Now I want to add ...
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14 views

Low air flow from the 2nd floor bathroom register and I can't find where it connects to the main air supply duct

My air supply system is very straightforward, with an extended plenum in the basement ceiling with 13 branch ducts. But, the house has 14 registers. There are 5 registers on the second floor but only ...
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0answers
28 views

Condo fan coil thermostat fan never turns off, cooling is humid

My thermostat in my condo is a honeywell thermostat and it the only options it has are System and Fan. Fan is set to auto (other option is Lo Med Hi) and the System is set to Cool (or Auto or Off). ...
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1answer
36 views

External Air Conditioner Condenser Capacitor replacement

I have a couple of questions about testing and replacing the capacitor on my home heat pump external condenser unit. 1. How can I reliably test the capacitor (what tools do I need?) 2. What safety ...
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1answer
29 views

A/C capacitor replacement

Can a CBB65 55+15uF+/-5% 250VAC 40/70/21 dual capacitor in a window mounted a/c unit be replaced with a 50+15uF +/-5% 250 VAC 40/70/21 safely?
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2answers
55 views

Can I pull a common wire off an evaporative cooler transformer relay?

I have a Nest thermostat currently controlling a LP furnace. The old thermostat didn't have a common wire connected, but there was a an extra wire in the bundle and a common terminal on the furnace ...
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1answer
54 views

Is it more efficient to turn my AC unit off periodically vs. keeping it on only while in the room?

I have an AC unit in my bedroom + workspace. I use its "auto" fan speed and "energy saver" mode (rather than "cool" or "fan only"). I'm wondering, which strategy is more energy efficient and by ...
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0answers
14 views

water in insulation boards - best method to dry out

I have a horizontal flow brand-new HVAC unit, with a 1" thick insulation board plenum which has had some water ingestion on the bottom panel. The unit is in the attic. I'm quite confident the water ...
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1answer
33 views

HVAC Air Blowback

Furnace/Blower: Rheem R92PA0851521MSA Dual Zone System (Honeywell TrueZONE HZ311) - Honeywell M847D1004 Actuators Age of system: less than 2 years old including ductwork Ive noticed that if Zone 1 ...
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1answer
31 views

Could my furnace be leaking due to condensation neutralizer?

I posted this and the main suspect was condensation pump but after troubleshooting, the pump is working fine (tested standalone). Now I wonder if the leak could be due to the condensation neutralizer; ...
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23 views

HVAC Second Floor Poor AC/Heat

I have one middle bedroom second floor that virtually gets no forced air AC or heat. Placing you hand on the reister you don't feel no force, very little air push. I on more than one occasion have ...
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1answer
88 views

Mysterious Metal Plate on Basement Ceiling?

There is a metal plate on the top of my basement's celing. It is attached to the HVAC ducts, but doesn't appear to be a duct itself. I'm interested in using the stud it is attached to hang an LED ...
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1answer
93 views

Is my furnace leaking water?

I have water accumulated in my basement, that I squeezed out using towel. It was about 8 gallons of water in all. The only source I can see is the furnace whose surrounding is wet but I have never ...
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1answer
38 views

A/C Fan won't turn on outside after replacing capacitor

I know this is a DIY stack exchange, and to be forthright, I did not DIY this initial repair because I was intimidated by replacing a capacitor, so I called a recommended technician who did the job ...
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2answers
68 views

Central AC Unit - Intake is very cold

So my central AC unit started doing something that I have not experienced before. Once the AC stops, cold air comes out of the intake vent, like really cold air. This has lead to ice forming on the ...
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1answer
59 views

Why the noises in the new furnace?

A company installed a new HVAC system 2 weeks ago. The furnace model was new: 58TNOA110C21–20. I initially ordered 58CVA110-20 but they said it will be out of market soon in August. So they installed ...
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1answer
79 views

Competing conditioned/combustion air flow; worry about CO?

My home has a partially-below grade basement that has a "Wave" ventilation system that brings cool, conditioned air in from the main house. The basement has an equipment room containing an oil burning ...
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0answers
77 views

The new AC doesn't cool the house down like old unit, what can be the problem?

I had to replace my old HVAC because it was old and had a freon leak. The new unit doesn't cool down the house like the old system. The ac runs all day and it takes hours to get down to 72 degrees and ...
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1answer
31 views

How to retrofit existing kitchen exhaust fan

I'm remodeling a kitchen that is circa 1940's. In the kitchen is an exhaust fan that sits inside a 3.25x10 duct. I would like to keep an exhaust fan in this location and re-use the existing duct, ...
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0answers
18 views

Spacing between supply line/cold air return

Is there a minimum spacing that should be followed when installing a new supply line into a room? I'm remodeling my basement and have two supply vents in the ceiling, but wanted to add 1 or 2 near ...
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1answer
52 views

Another “How do I add ”c" wire to boiler for Nest

I have tried searching this forum and others, but I could not find anyone with a situation like mine. I thought it better to ask here, rather than damage something. I have a Lennox wall mounted ...
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1answer
23 views

3-zone HVAC (HZ432) one zone's a/c stops working when hot in afternoon

I have a 3-zone HVAC. All 3 zones a/c worked fine until recently. Now, in the morning, before it gets too hot, all zones still work fine. But in the afternoon, when it gets hot, the a/c to zone 2 ...
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1answer
53 views

New HVAC installed [closed]

I just had a new HVAC system installed and the contractor installed in on a pounding raining stormy day. I am thinking that was a bad decision on his part. Now my home has a musty smell and air ...
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0answers
27 views

Door to AC unit causing pressure change?

Found water in the bottom of my AC unit inside. When I remove the bottom door the water will run back to the drain. But when I put the door back on, the water is being sucked down by the motor. There ...
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0answers
34 views

Furnace blower cutting in and out during A/C use

Backstory: I fired up my air condition for the first time this season (single family house) and felt lukewarm air coming out of my ducts. When i went outside i saw that the condenser was not turning ...
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1answer
36 views

Running AC/Heater when washing a cleanable filter

I have a heat pump/AC system with a washable air filter. I was told to clean the filter out and run water through it once a month. He told me to let the filter dry for 3 hours before replacing it. I ...
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0answers
11 views

Hvac condensate line not draining, New ac system

Hi so I just purchased a house. It was a bank foreclosure. The bank installed a new ac unit. The ac wasn't running in day one. I figured out it was bc the condensate line wasn't draining properly. The ...
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3answers
151 views

Is there such a thing as a DIY heat pump or mini split

I wanted to ask this question to the community. Is there a legal way to install a mini split or heat pump without having an EPA license? I have seen similar questions asked several times or ...
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1answer
31 views

What's the easiest way to trace out existing HVAC ductwork without cutting into the walls

I recently bought a multi-story house with a 4 zone HVAC and only one of the zones works (it just heats/cools the entire house as one zone, and the one working zone is for a small foyer which is ...
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1answer
25 views

Window air condition location placement question

1800 sqft + basement On main floor 2 window air conditioners 19k btu combined Upstairs 1 5k btu air condition There is 3 bedrooms upstairs, does it make sense to jist pit all the ac units upstairs ...
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54 views

HVAC Exhaust Routing Question

Just wondering if I could get some advice on the optimal way to route the HVAC Exhaust piping. Enbridge replaced the supports underground and before they turned the gas back on they did an inspection ...
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0answers
26 views

Separate Thermostats for Heating and A/C

I recently purchased a vacation home that has two thermostats for a forced hot air gas furnace and a separate A/C unit that shares ductwork. The A/C also cools better when both the A/C and furnace fan ...
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0answers
52 views

Does cabling between a mini-split indoor and outdoor unit need conduit?

I am installing a mini-split AC system where there are multiple indoor units connected to a single outdoor unit. For each indoor unit, there is a separate 4-conductor cable that connects to the ...
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1answer
41 views

AC Condensate Line Location - Outside vs Inside

I'm installing a few mini-split AC units in my house, and I'm trying to determine the best place to run the condensate line. Right now it's either between running it outside with the line set and tray ...
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2answers
65 views

Why would my HVAC blower motor stop working after 10 minutes of runtime

my 2 year old unit it freezing after it’s been running about 10 minutes. I turned the unit off all last night. This morning I took a look at it outside, then went back in, turned it on, sat by the ...
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2answers
39 views

Can the wire from the y terminal on thermostat be connected to the c terminal on heater board as pictures show?

My nest was installed with no c wire and it lost power. At this point the tech looked at the wiring diagram in a/c unit outside but I do not know what he did. A/c worked but later nest had no power. I ...
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1answer
36 views

Install a Wi Fi thermostat

Trying to install a WiFi thermostat. I have the unused blue wire which I believe is the common wire. It is unused both and the furnace level as well as on my current thermostat. However there is ...
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0answers
34 views

Installed NEST thermostat heat works fine, AC compressor comes on but no fan on AC unit

I installed a new NEST thermostat last fall so only used it for heat so far. When I went to turn on AC, compressor came on but AC unit fan didn't. AC worked fine last year. Could this be a NEST ...
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2answers
100 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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0answers
37 views

Dedicated 240v 30A Circuit Switched for A/C and NEMA 14-30 [duplicate]

I have a dedicated 240 volt circuit that's hard wired into my air conditioning unit. The circuit has a 30 amp breaker at the main box and another 30 amp breaker on the wall next to my air conditioner....
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1answer
25 views

How do I determine where to connect a new C wire inside my furnace when no control panel or wiring terminal exists?

I am replacing my existing thermostat with a new smart thermostat that requires a C wire connection and the old unit did not. I intended to utilize the unused Blue wire which is not connected on ...
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0answers
39 views

air handler not turning on

Assume an ac compressor doesn't work. Will the air handler still come on if the thermostat is set to fan "on"? Does this differ system to system? I am trying to troubleshoot a non-responsive ac ...
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2answers
128 views

How do I deaden the sound of water dripping on metal?

I live in a two story apartment complex (upstairs neighbors are REAL nice). My bedroom has an AC Box/Swamp Cooler mounted into the wall. Directly above it is a similar unit for my neighbors. The ...
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1answer
83 views

Best air conditioner for cold blasts?

The old air conditioners I had could blow out snow literally that is how cold they got, now air conditions are only moderately cold. What would be the best system to get to just blast one giant vent ...
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1answer
63 views

Why is my AC only blowing out Ice cold air and freezing over AC lines?

I've had a company come out and tell me the ac and furnace are ran from 2 different fans and they recharged the AC unit. However, prior to this the AC was still freezing over the lines. If I have the ...
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0answers
45 views

Wand or 2 foot long stick between my master bath fan and outdoor flood lights connecting to share wiring for power?

I'm divorced. My ex husband had a guy install a junction box on corner of house to spotlight the swing set years ago. Recently I was in the attic and discoved a 2 ft "stick' or "wand' that was quite ...
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1answer
53 views

Line to AC dripping at the furnace

My line from my exterior AC unit is dripping at the furnace. The dripping over time has caused rusting and we've had to replace the control board under it. It appears the root cause of the problem ...
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1answer
74 views

Air Filter size for (new to me) home HVAC

My wife and I just purchased / moved into a new house and I was going through each of the systems and found the HVAC filter, it was literally destroyed (it had filled with crap and crushed itself in ...
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25 views

Rough in bathroom exhaust

So, I have a pretty basic question that I can't really figure out for some reason. Is there a way to rough in bathroom exhaust fans before siding? In other words, there are trim kits for sconces, ...