Questions tagged [hvac]

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

402 questions with no upvoted or accepted answers
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90 views

Why don't HVAC service people want to use outdoor temperature sensors to increase efficiency?

Here in central Virginia, most houses use heat pumps with electric auxiliary heat. I have inquired with several different contractors about installing outdoor thermostats on my units to 1) disable ...
4
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0answers
2k 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
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1answer
161 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
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0answers
49 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
99 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
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1answer
289 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
2answers
265 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
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0answers
28 views

How to wire Aprilaire 600a to older furnace

I need help wiring an Aprilaire 600a humidifier yo my older oil furnace (from 1998). I thought I had followed the wiring instructions properly, but the digital humidistat is giving me an error code (...
2
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0answers
16 views

Water not circulating through baseboards

2 zone (1 radiant floor, 1 baseboards) hot water heating system. Radiant floor (t’d off main feed) seems to be working fine. None of the baseboard loops are hot, and the pipe was hot before the ...
2
votes
2answers
58 views

wiring furnace blower to turn on when make up air damper is powered to open

I have a make up air damper that is opened to supply make up air to the system return air duct when the kitchen range hood is operating. There is a pressure sensor in the range hood vent duct that ...
2
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0answers
28 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
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2answers
75 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
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0answers
36 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
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0answers
18 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
113 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
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2answers
223 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
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0answers
109 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
90 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
86 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
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0answers
67 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
250 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
1answer
602 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
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0answers
518 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
138 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
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0answers
7k 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
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0answers
2k 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
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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
562 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
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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
589 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
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0answers
860 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 ...
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0answers
29 views

How to accurately measure CFM with Digital Anemometer and Duct

We bought a digital anemometer to check the CFM of various fans we have on hand. My husband designed and 3D Printed this duct that securely mounts fans on to the anemometer for accurate readings, ...
1
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2answers
51 views

Plaster Walls Cracking above air vents

My house was built in the 1950's and have plaster walls. I am in the process of repainting and have noticed that the plaster above the baseboard air vents has cracked above almost every vent in the ...
1
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0answers
19 views

wiring up new air mover

I have a central air system and my squirrel cage fan inside the house started humming and then stopped. I figured it was the capacitor but I found a whole new fan for just a little more. Im having ...
1
vote
1answer
56 views

Sticky black liquid coming from Furnace / AC Unit

I have this sticky black liquid slowly leaking from my gas furnace / ac unit. I called an HVAC repairman and he wasn’t sure what it was. He said he thinks it’s an old drip pan made of tar (not sure ...
1
vote
1answer
31 views

Forced Hot Air temp out of vents seems too hot

Vents close to heater the temp is up to 130 F. Others further away are less than 100. 130 F just seems so hot metal, registrar would burn your hand if you left it touching. Heater has to run over 7 ...
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0answers
10 views

Heating system cycling

My heating system is power cycling because the heat exhaust temperature sensor is tripping. When I turn the intake gas valve closed a bit, the system will stay on for longer but it's still does some ...
1
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0answers
29 views

Thermostats with or without variable temperature differential (swing)

I am looking at replacing my thermostat, and don't really need or want one with geosync. I am thinking of the honeywell RTH9585wf. Currently I have a lux that is not wifi but programmable. It ...
1
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0answers
19 views

AC compressor runs with heat on. NOT a heat pump

My AC compressor recently started running whenever the heat kicks on. It is not a heat pump. The compressor is a Nordyne fs3ba-036ka. I haven't done anything to the system aside from changing filters ...
1
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0answers
24 views

Furnace sometimes does not start

I have a 5 year old Broan furnace model M7RL 072A AW downflow condensing gas furnace. Here's the furnace startup sequence: pump runs ignitor glows hear the click of the gas valve opening fires up ...
1
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0answers
35 views

Very Old thermostat with TR wires

I want to buy a new smart thermostat, but am confused on the old wiring. I have single zone 120year old gas boiler (converted from coal, then oil, now gas). No cooling. The old honeywell thermostat is ...
1
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0answers
25 views

Suggestions on where to relocate a wall register I'm enclosing in a closet? (with labeled floor plan attached). Thank you!

I'm looking for some suggestions on where to relocate the HVAC wall register (shown in red), as I am planning to enclose it in a closet. It comes from 3x7 rectangular duct into the 2x4 wall and rests ...
1
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0answers
32 views

HVAC duct sizing

I have a 4 ton American Standard electric forced air furnace (with no A/C - just heat) with a single speed blower motor, circa 2006. My supply main trunk is 12"x20". The return side of the system ...
1
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0answers
16 views

PTAC heat troubleshooting

I own a condo with two Islandaire EZ09EBMXH8N10AA PTACs, one of which is acting weird. They have self-contained A/C mechanisms, but the rooms are heated by pumping hot water from the building through ...
1
vote
1answer
98 views

Can I manually switch off booster fans that are coupled with HVAC blower?

Could not get upstairs in 1900 craftsman bungalow cooled with HVAC system until the contractor inserted a booster fan in each of the two ducts. Fans are coupled to the blower of the HVAC. Now in fall ...
1
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0answers
23 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
98 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
62 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
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0answers
25 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
56 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 ...

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