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

learn more… | top users | synonyms

1
vote
2answers
124 views

How to seal HVAC ducts running through old window to addition?

My house has a small addition that was added by the previous owners. They ran the HVAC ducts through an old window and some of the block: The rectangular section in the window should be easy ...
0
votes
2answers
398 views

G to C trick not working for cooling. Honeywell RTH9080WF

My electric furnace has no c terminal. Furnace is heat & cool both. (Lennox Electric Fan coil Model CBS18-21-3P). I installed Honeywell RTH9080WF. I switched G to C on my thermostat and got the ...
3
votes
1answer
156 views

Is there a wireless way to cut off the HVAC y wire from my generator transfer switch?

I recently had a Generac Synergy generator installed, which went smoothly, however there was no good way to get the Y wire from my thermostat to the transfer switch and back in order to allow the ...
11
votes
6answers
29k views

Does lowering the blower speed of a forced-air furnace lower its efficiency?

My gas furnace has two options for the blower speed: MED, and MED-HI. It had been set on the higher speed, but that was too harsh, so I lowered it to the slower speed. Does that have any impact on the ...
1
vote
1answer
128 views

Chattering contactor, what should voltage be when AC is on/off?

I have a Nest thermostat that I believe is the culprit of this issue. I've already replaced the contactor once and now the new one is chattering and not kicking the AC on. When the AC is turned off, ...
1
vote
1answer
6k views

Why is my furnace blower running at low speed?

My Payne gas furnace (PG8UAA 42091) automatically shuts down after it lights and burns for two minutes. It then gives a 33 fault code. I've done some research and some testing and have narrowed the ...
4
votes
8answers
11k views

Would putting a sprinkler on my roof help cool my home?

Anyone ever put a sprinkler on your roof to help out your A/C on unusually hot days? Just wondering if it helps.
2
votes
5answers
23k views

How do I wire an old furnace motor so I can use it as a garage exhaust fan?

Since last I posted, I moved WAY south (lil warm down here) and the house I moved into was a foreclosure so a few things needed done, namely the AC and furnace. When the guy did the job he said he ...
1
vote
1answer
156 views

What should I do after a low-voltage wire was cut putting the furnace door back on?

I have the basic Honeywell thermostat that a lot of people have. All the thermostat wires go to the blower in the attic (for the central air). They are spliced with wires that then go to the furnace. ...
0
votes
4answers
877 views

HVAC supply vent noise: how to eliminate the whistling wind tunnel?

Every time the heat turns on (rented house), we are getting choked with too much dry hot air in our small room. When I try to close the supply vent it produces a really loud whistling noise. I either ...
1
vote
1answer
57 views

Actual efficiency of an old oil furnace?

We purchased a house with what appeared to be a relatively well-maintained oil furnace, about 30 years old (installed in 1984). We don't have any records of annual oil usage, or any way to find that ...
0
votes
3answers
90 views

My Goodman a/c motor fails due to high voltage

I have got a brand new goodman unit. The motor kept stopping after few hours an the tech replaced the motor. It still had same issues.. I was told that the voltage coming into the unit is too high.. ...
0
votes
0answers
24 views

coleman furnace model dgaa furnace heats up and shuts down berfore blower starts and flashes code 4

york DGAA will work fine until it gets close to hot enough for the blower to turn on. I said close to turning on because I think it should get hotter but I'm not sure just guessing. The upper limit ...
0
votes
3answers
147 views

Is an HVAC license required for DIY home owner AC installation in the State of Georgia?

Does anybody know for certain if in the State of Georgia, an HVAC ("conditioned air") license is required in order for a homeowner to install their own HVAC system?
2
votes
2answers
1k views

How can I wire my WIFI thermostat to control my millivolt fireplace?

I have a gas fireplace that has an millivolt on/off switch on my wall (and a remote that includes flame on/off, a countdown timer and a thermostatic flame control). I want to be able to program ...
0
votes
1answer
104 views

Air Conditioning Drain Pump

I am going to purchase Multi-Split air conditioning unit for my apartment that I am fully renovating at the moment. So it is the right time to make wholes in the walls etc. The supplier is giving an ...
1
vote
0answers
35 views

Mini Split condensate pump to condensate drain

I'm working out the details of my Mini split. I know by code I have to have it connected to a 3/4" condensate line going outside. The Mini Split's air handler is located on an inside room where I'm ...
1
vote
3answers
123 views

Heat Pump - emergency electric strips - how controlled?

I have a recently installed combination of a Goodman electric package unit, and an ecobee smart thermostat. This morning with the outdoor temp at 36, I was surprised when I peered out the window and ...
0
votes
1answer
118 views

What is the rated power of American central air-conditioning control circuit?

I want to know what is the rated power that American central air-conditioning 24V control circuit can supply, which is also the power supply for Nest. Nest gets its power from the 24V control ...
1
vote
1answer
78 views

Emergency Heat Coils vs Space Heaters

I have two heat pumps, in an all electric house. Unfortunately they both seemed to have stopped working at nearly exactly the same time. I have called for qualified repairman, but they won't be out to ...
1
vote
2answers
451 views

Why does my shower run out of hot water quickly?

My shower runs out of hot water quickly. Initially the water is perfectly hot, then it starts cooling after a minute or so and we need to adjust the lever to maintain the temperature. Somewhere around ...
1
vote
1answer
322 views

Why would a blower motor work with A/C, but burn out with furnace?

I've gone through 2 blower motors since I purchased the home 3 yrs ago. I never have an issue with the blower when the AC runs; but it keeps dying in the winter with the furnace. I've had 2 HVAC ...
11
votes
4answers
10k views

Ethernet cable instead of Thermostat wire?

I need to pull new wire from my furnace to my thermostat and was wondering if there would be any problems in using an Ethernet cable instead of standard thermostat wiring. The reason being is I have ...
1
vote
1answer
167 views

Where does the C wire connect in a dual transformer system?

When wiring a common ground (C wire) for a dual transformer system, does it matter which transformer you connect the ground too? I'd assume that the ground on either transformer would serve as a ...
1
vote
1answer
42 views

Access 2nd-story burst hydronic pipe through ceiling or floor?

We had a freeze which caused one or more bursts in our hydronic heating system pipes. We know that there is one burst in a radiator, but there may be others, according to the contractors. If there is ...
2
votes
1answer
38 views

0v at DC thermostat terminal in furnace

I have an old (mid 80s) Rheem gas furnace I hope will last me through at least one more California winter. It's been known to go down into the upper fifties, so it has its work cut out for it. In any ...
0
votes
1answer
60 views

Furnace Fuse Blows Immediately

This afternoon, our Ruud furnace suddenly stopped working. After poking around a bit, I realized that the 3A fuse on the control board had blown. I ran to the hardware store and replaced it, but no ...
0
votes
1answer
120 views

noisy Air-conditioner compressor

I bought a new split AC that worked great for a week or so, but now I can hear some annoying noise coming from the outdoor unit. The outdoor unit in installed on a flat roof so I can hear this noise ...
0
votes
1answer
30 views

Central air winterization and insulation

Do I need to insulate the skinny copper line on the outside to keep it from freezing and bursting during the cold winter months? Anything else I need to do winterize the a.c. unit?
0
votes
0answers
217 views

No C wire terminal on my electric plenum but there is on my furnace. How do I solve?

I had a brand new furnace installed recently but also now picked up a wifi thermostat. The problem I now encountered while installing the thermostat is that my system also has an electric plenum as ...
1
vote
0answers
28 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 ...
0
votes
3answers
189 views

What are the possible reasons I am not getting cold air from my air conditioner?

my heat pump outside is working but my central air conditioning/heating unit in the garage makes a hissing sound or faint sound of water running. There is air coming from the vents. The very last time ...
2
votes
1answer
231 views

What is the optimal duty cycle for a furnace?

A heat load calculation of my home says it requires ~36K BTU/hr of heat at a normal winter temperature (40°F), and ~52K BTU/hr at the design temperature (24°F). An HVAC contractor has proposed ...
1
vote
2answers
104 views

Can the A/C temperature through a vent be significantly lower than in the air handler?

Can the A/C temperature coming out a vent be significantly lower than the temperature in the air handler above the evaporator coil? If so, how does the air get colder as it comes out the vent? Or ...
2
votes
1answer
39 views

If water level is rising on its own on oil heating unit instead of going down, could I have a leak? Or something worse?

If water level is rising instead of lowering on oil heater unit, is there a leak? Could something worse happen. Oil man had to drain water to lower water, and said to watch it to make sure it doesn't ...
1
vote
2answers
212 views

HVAC unit won't come on

This morning I noticed that my main floor wasn't cooling. I found the condensation pump full ( little giant model VCMA-15ULS ). I disconnected the hose from the unit to the pump, drained it, dumped ...
1
vote
1answer
60 views

How do I compare furnace models?

I need a new furnace, and I have quotes from two companies, for three different brands of furnace, Carrier, Trane, and Lennox. Both companies have provided the model numbers of the units they would ...
1
vote
0answers
21 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 ...
1
vote
1answer
119 views

How can I better control temperature differences between floors in my two story home that has two HVAC systems?

We have 2600 sq ft on the main level and 800 on the 2nd floor. To the 2nd floor, there is a staircase and with a door on the bottom floor. We have our master upstairs and don't use the room at all ...
0
votes
0answers
132 views

What makes a furnace pilot valve whistle?

I have a furnace that started whistling, recently. I have read that gas pressure changes can cause this. Others have remarked how seasonal gas changes can lead to a properly-adjusted furnace to ...
0
votes
0answers
18 views

Installing a Wifi Honeywell Thermostat with a C wire [duplicate]

can someone please help me out here. I'm installing a Honeywell Wi-Fi Thermostat and this Thermostat requires a "C" Wire. Can someone please tell me by looking at the pictures attached if I have a "C" ...
1
vote
1answer
378 views

heat pump/air conditioning wiring to thermostat

We decided to change the thermostat of our heat pump/air conditionnning unit. First 3 images are the old unit. The first 3 wires(1 and 2 picture) yellow red orange were not connected to anything, just ...
1
vote
2answers
1k views

Can I convert a window A/C unit in to a pool-water cooled system?

I have an 18,000 BTU A/C unit that blew a compressor last year. Perfect for a small project. I however could not find a professional to help me out, so maybe it's DIYable. I know just about enough ...
0
votes
1answer
49 views

Does cold galvanizing compound restore the rust protection of a galvanized duct?

The house is a ranch built on slab on grade with a newer furnace in a downflow configuration with A/C. The in-floor clay tile supply lines are in good shape and clean. The original 60 year old ...
1
vote
1answer
147 views

New thermostat wire: maximum number of wires?

Background: I'm upgrading from a failing ecobee smart thermostat to an ecobee3. The ecobee3 requires all wires for the components it controls to be run all the way to the thermostat (including ...
0
votes
1answer
938 views

Where is my common wire on the unit?

I have 2 systems in my house, my heat is gas hot water radiator heating and A/C is a separate newer system. I'm trying to figure out if I can run a C wire off air handler from the A/C system to run ...
0
votes
2answers
109 views

Is the Thermostat Wiring Correct

When I moved in to the house the first thing I changed was the old mercury style T-stat to a digital one, I went wire for wire, and it has works (knocks on wood) so far. Now that I have been reading ...
0
votes
0answers
28 views

Pellet Stove Ventilation

I have an Englander PDVC pellet stove that came with my house when I bought it in the spring. Never used it. Currently its vented through the wall and comes straight through the exterior of the ...
1
vote
1answer
111 views

Which direction is the airflow through my furnace?

There's multiple lines of ductwork along the side, and up top. So what's the correct direction of airflow (red or green in the image below)?
0
votes
2answers
635 views

How do I cut a straight line in an installed wood floor for a flush mount HVAC vent?

At some point a previous owner installed hardwood flooring in my house. Nice. They did not however make a hole for the front entryway heating vent. The duct and duct outlet exists in the crawlspace ...