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Questions tagged [hvac]

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

391 questions with no upvoted or accepted answers
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5
votes
1answer
218 views

Adding a C wire to older 3 wire

How do I use the green wire as a C wire as suggested in most installation instructions for the newer wi-fi thermostats? They all reference terminal strips at the furnace, all I have is the 3 wire ...
4
votes
2answers
131 views

Is this HVAC condensing unit platform acceptable/stable enough?

Our contractor just installed a new A/C system and he built this platform outside our house for the new condensing unit. It looks like it is a 4" concrete slab sitting on top of brick "legs". Looks ...
3
votes
1answer
58 views

Furnace Connect G Wire

I have a dual energy electric/oil furnace that is wired to a thermostat with 2 wires R and W. I don't have any AC. Inside the furnace there is a switch relay to control the fan but it is not connected ...
3
votes
0answers
42 views

Why isn't my furnace igniting?

I noticed cold air from my Carrier 58SS furnace. The main burners were not lighting. The pilot flame was strong, but yellow. When I tapped on the gas valve, the pilot shut off. I removed the pilot ...
3
votes
2answers
85 views

Thermostat White-Rodgers 1F82-261 switches to stage 2 heat for no apparent reason

I am running a central heat system that uses a heat pump as stage 1 and a gas furnace as stage 2. The thermostat used is the White-Rodgers 1F82-261 which supports 2 stages of heat. When using regular ...
3
votes
1answer
194 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 ...
3
votes
0answers
1k views

Difference Between Take Off and Starting Collar - Which One Should I Use?

I am in the process of installing a whole house humidifier. I am planning to mount it to the supply side and need to connect the bypass to the return. I'm not sure if I should be using a take-off or ...
3
votes
2answers
262 views

A/C unit cycles on and off during cooling phase

My outside compressor / condenser is cycling on and off, even though the thermostat is calling for A/C. The blower in the house still runs, and the thermostat is working properly. (I opened up the ...
2
votes
0answers
25 views

New thermostat turns fan off when set to on, never turns off on auto

My oil heat furnace was functioning normally on an old mercury switch thermostat, but I wanted to replace it with a programmable Honeywell 5+2 one. There were Y, W, G, R, and B wires screwed in on the ...
2
votes
2answers
65 views

HVAC AC Capacitor Replacement

I have a Carrier Infinity Series AC Unit (Model #: 24ANA748A0030020 or 24ANA748A00300); its capacitor needs replacement. I live in Chicago; so VAC is 120 x 2. Current Capacitor Specification: ...
2
votes
0answers
34 views

New Unit with Blocked Condensate Lines

A little over 30 days ago a new HVAC unit was installed at my home. Saturday night I had a buckled ceiling and a BIG problem. The installer told me both primary and secondary lines were clogged—-the ...
2
votes
0answers
16 views

Trane HVAC in horizontal position - why does evaporator throw condensation?

I appreciate assistance from anyone who has had or understands the problem. I have a Trane HVAC system in a horizontal "left" flow configuration in the attic. Ambient temperature is about 95 ...
2
votes
1answer
58 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 ...
2
votes
2answers
95 views

Should I insulate metal duct work in basement?

I have a balloon frame house with an unfinished basement. The air handler and furnace are in the basement too. Last fall, we had the duct work removed because it was wrapped in asbestos tape that ...
2
votes
0answers
92 views

Junction Box Blank Cover in HVAC Duct

I am starting a bathroom remodel second story that requires a length of NM wire to be lengthened by a few feet. I realize I can't do this hidden in a wall or floor and need this done in accessible ...
2
votes
1answer
69 views

Solar panel as a hatch and Is sleeping under a solar panel safe?

I'm looking to build a very large custom roof hatch/vent on my van. I was going to make to top out of Lexan, but then I realized I might want a large solar panel on the roof as well. I was looking at ...
2
votes
1answer
235 views

Ecobee Smart Thermostat- Using Room Sensor as primary control

This is ultimately a fairly simple question about the Ecobee3 thermostat and the wireless room sensor functionality, but I'll explain my situation first. Twin home, 2 stories + finished below grade ...
2
votes
0answers
63 views

Mini-split HVAC in new build?

Next few weeks I will be in the process of getting quotes for mini-split HVAC system. Curious, if anyone has gone ductless and if so, how is that working out? The house will be a a two story build(...
2
votes
0answers
59 views

Replacing a motherboard on a Carrier 8000VS Furnace

Hi guys, I am trying to finalize the wiring of my new carrier motherboard. I have about four more wires to connect and the new motherboard is slightly different than the old one. The pictures I’ve ...
2
votes
2answers
216 views

Lennox G23Q3/4-100-2 And Ecobee4

**Pictures attached to go along with my rambling explanation I have my Lennox G23Q3/4-100-2 natural gas furnace and my central air system that has been working since 1995 on a basic programmable ...
2
votes
4answers
2k views

Why does my furnace turn off after a few minutes, then re-ignite?

I have a Goodman 80% furnace in my barn dated 1999 it runs for about 5-10 minutes then flame kicks off for about 2 minutes and re-lights. It does not go into lockout mode (keeps cycling this way). ...
2
votes
1answer
547 views

Can I install a heat-recovery ventilator (HRV) in a garage?

I am building a high efficiency home in N. Minnesota, 2x6 construction, slab heat, spray foam insulation etc. Need to install an heat-recovery ventilator (HRV) unit, but only have space for it in the ...
2
votes
0answers
471 views

Installing Ecobee3 with Trane Furance

I am installing an Ecobee3 and have found that, while the common wire exists, it is not connect to the furnace. The wiring schematic for my specific furnace can be found in this PDF There is no ...
2
votes
2answers
127 views

Misbehaving/inaccurate thermostat?

I have a portable air conditioner/hvac and I'm having issues with it in heating mode. It's actually summer where I live but it was somewhat chilly as a storm passed over so I wanted to test heating on ...
2
votes
0answers
6k views

Increasing gas pipe size from 1/2“ to 3/4” at appliance

I'm planning to purchase and install a new condensing tankless water heater (Takagi T-H3J-DV-N) that will supply both domestic hot water and space heating (radiant via heat exchanger, separate closed ...
2
votes
0answers
1k views

Trane Weathertron Stat to Honeywell RTH2510

I have a Trane Weathertron thermostat thst I am replacing with a New Honeywell RTH2510. This is a heat pump with auxiliary electric heat. The wires on the Tran thermostat are. R, T, O, G, Y, B, X2 ...
2
votes
0answers
73 views

Air handler for an AC in the attic collect about 1 cm of water in it before it is high enough to drain… problem?

My air handler in my attic won't drain water(because the hole is 1cm above the pan) until the water reaches that hole. Why is this setup this way. From what I have read, NO water should be in the ...
2
votes
1answer
798 views

Want to add a WIFI thermostat, but no 'C' wire… only 2 wires to each thermo

i have a 5 zone radiant floor, oil fired heating system. Each thermostat only has 2 wires running to it. i have a TACO SR506 switching relay that receives the wires from each thermostat and controls ...
2
votes
1answer
533 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
2
votes
0answers
3k views

Reducing air conditioner compressor vibration noise

I have a two year old Carrier air conditioner with an outdoor condenser. The condenser sits on a plastic pad on the side of my house, and I have two--one for downstairs and one for upstairs. ...
2
votes
0answers
578 views

How can I insulate and elevate an A/C line set on a flat rubber roof?

The Scenario An apartment building with a flat black rubber roof. The A/C condenser is on a platform on the roof with an air handler inside the unit. The line set runs across the roof for about 20 ...
2
votes
0answers
858 views

What are good Relative Humidity and Temperature settings on an MHRV and are the settings related?

I need to configure the threshold Relative Humidity and Temperature settings on an whole house MHRV system. The way the system works is that if the RH threshold is exceeded the system increases the ...
1
vote
0answers
10 views

Lennox G51MP shutting down with Primary/secondary switch fault

I have Lennox G51MP-48c-090-06 ~14yrs old, starting up for first time this season. It is throwing error code: Primary or secondary limit switch open. Unit shows normal operation when powered up and ...
1
vote
1answer
42 views

Where should I connect my C-wire on my old Goodman unit (GMP075-4 rev 13)

I want see if someone help me on hooking up this new Honeywell thermostat with Wifi I just purchased. I have an old ac unit and I only have 3 connections to my circuit board which does not have an ...
1
vote
0answers
60 views

No power to isolator switch

I recently moved into a repossessed flat and the electrics were a bit of a mess. Sockets, switches, etc. hanging off walls but it has since all been made safe/good by an electrician. The only thing ...
1
vote
0answers
19 views

Eliminate Humidistat

I have an old Honeywell H8808 humidistat and a Pro 1 model T721 thermostat and the problem is that when the humidistat is turned down far enough to kick the system on it will come down to set ...
1
vote
1answer
45 views

Why is my HI HEAT terminal causing blower to run non-stop?

I am trying to troubleshoot what is causing my blower to run non stop (the condenser (outside unit) comes on only when cool is required). There is no issue with cooling the house. I read through all ...
1
vote
0answers
63 views

Why is my HVAC system not turning on the A/C compressor?

My AC stop cooling. Here's what I found. Inside blower is working, outside compressor/fan does not turn on. I manually push the contacts in the outside relay and the compressor and fan worked, used ...
1
vote
0answers
48 views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
1
vote
1answer
21 views

Fan on propane furnace not coming on

I have a Honeywell model number NHGK076AF01 propane furnace. It is about 15 years old. The problem started when I noticed the breaker had tripped and I had no heat. After resetting breaker, I tried ...
1
vote
1answer
191 views

Central Air is Blowing cold air outside

I change the capacitor and cleaned all of the coils inside the interior unit and outside along with the fins and the blades with a professional solution. I had the HVAC refrigerant filled. I cleaned ...
1
vote
1answer
36 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 ...
1
vote
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 ...
1
vote
0answers
78 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 ...
1
vote
1answer
25 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 ...
1
vote
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 ...
1
vote
0answers
27 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 ...
1
vote
0answers
85 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 ...
1
vote
1answer
56 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 ...
1
vote
0answers
33 views

Problem connection C wire into Lennox Furnace

I would like to connect my new Honeywell WiFi thermostat (RTH6580WF1001) to a Lennox Elite dual Heater and Cooler system. I don’t have a C wire in my old thermostat. I have read online that I can ...