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

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1answer
119 views

How to Change Chinese HVAC Thermostat

I am looking to put Nest thermostats in the house, I have now found out my entire house (one in each room, 6 of them) has been wired with HVAC Chinese U12A UNIVERSAL A/C CONTROL SYSTEM urrgh – they ...
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0answers
9 views

In what circumstances would an AC produce no condense but it will still cool the air?

This is a brand new furnace which seems to have problems to turn off when it is set for temperatures below 77F. The unit can reach these temperatures but it does not turn off as it would in a normal ...
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1answer
5 views

My home air conditioner that's inside the house, seems to be sputtering when coming on. What could this be?

My home air conditioner inside the house; when it's going thru its normal cycle of off and on, it seems to be sputtering and/or hesitating to come on. It's like or similar to a car that having a hard ...
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2answers
13 views

Cooling radiators in summer?

How efficient would it be to use radiators circulating with cold water, to cool house in summer? Wondering if anyone has tried this, and how well it works? I was thinking about H/AC in general, and ...
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1answer
243 views

Central AC is Icing up, but not cooling my house

My central air conditioner isn't cooling like it used to. I noticed that the refrigerant lines entering the evaporator coil in the plenum were icing up. What might the problem be?
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1answer
13 views

help with improving HVAC performance on the second floor of an old house

I'm hoping some of you can offer some advice on how best to add a second AC in our home -- or on whether we should look for a different solution. I should say upfront that I've done a lot of reading ...
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1answer
36 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
8 views

Cleaning of TempStar air conditioning parts

It's been 6 years since I bought the Tempstar 4 ton a/c. So far, it is running okay. But when the need arises, I want to be BOLO and do the repairs myself. So, how do I clean a TempStar a/c ...
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1answer
24 views

How long should it take to a 1.5 tons AC to cool down a 2000sqf house from 80F to 77F?

I know that it might depend on a lot of things like: -how air tight is the house -how old it is (insulation, windows etc) -what windows are installed -BTW I have casement window -outdoor temp ...
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0answers
6 views

Does it make sense to add dumper fans for the return path of an AC? [on hold]

I just checked the registers on my return path for my AC and I can not say that I am happy with what could see in the basement. What are the pros and the cons of adding a duct/register fan to the ...
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1answer
26 views

Does the air temperature outside at the time of spring inspection matter when the tech comes to inspect and clean the inside and outside units?

I have semi annual inspections done on my A/C units both inside and outside. Will the temperature outside effect the tech's ability to properly clean and evaluate the operation of the units? The ...
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1answer
21 views

Are HVAC Transformers Interchangable (if their power ratings match)

I'm troubleshooting the blower not starting in a friend's HVAC system. We think the issue is either a) a blown transformer, or b) the relay that controls the blower has blown. The next step is to ...
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0answers
16 views

Both A/C air handler and outside unit won't turn on

I went to turn on my A/C for the first time this year, and nothing happened. I checked power to both the air handler and outside unit...both at getting 220v going into the boards on each. I then ...
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5answers
80k views

Why won't my A/C turn on after I replaced the thermostat batteries?

Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the LCD screen was operable, our AC no longer turns on. I have attempted a factory reset on ...
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1answer
175 views

Why isn't my Lennox G26Q3/4-100-6 furnace firing up?

I replaced the batteries, does not click when it calls for heat in the thermostat. fan blows but no heat. I took off inspection door, held the safety switch in, a blue light is blinking constantly, ...
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0answers
15 views

Need to find control valve for damper

There is no control valve attached to this damper: so I can't turn it to open/close the duct. It's currently closed :-(. It's smooth so I haven't found anything that can even grasp onto it tightly ...
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2answers
47 views

How to install small damper in a duct?

I need to install a Honeywell 10x10 damper into a 11x11 duct. Options that I came up with: build an adapter to reduce duct to 10x10 (alternatively I can use 12x12 damper and build adapter to ...
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0answers
58 views

AC Unit does not receive 24 volts on outside unit

My outside unit does not turn on itself, but it does work. I just did a quick repair just thinking it was the capacitor and it was only 15 dollars for a new one so I changed that out and still had the ...
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0answers
31 views

AC is freezing after one day of full use

I had my AC unit serviced two months ago. The unit is about three years old. This week is the first week we have had it turned on all day. Last Sunday I noticed that the AC was on, but no air was ...
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1answer
35 views

Should storm windows be removed if AC will be on and windows rarely opened?

We generally run our AC most of the day. I am wondering if it is a detriment to leave the storm windows on (b/c they create a pocket of hot air) or a potential benefit (by reducing the escape of cold ...
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3answers
87 views

Five Year Mystery - Unable to find source of burning smell from HVAC system

There is a burning smell that wafts out of the vents of my 15-year old, 3-level townhouse (top level is a full unfinished attic with no HVAC). The bottom level of the townhouse is the main level ...
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1answer
16 views

HVAC compressor turns on when calling for fan only

I just moved into a new apartment with HVAC, and I'm looking to control the thermostat with a few Phidgets (I had already invested in that ecosystem, so I just needed a couple of relays). Anyway, ...
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1answer
274 views

Fan coil wiring problem with new thermostat

I'm trying to upgrade to a new line voltage thermostat. The new thermostat has many more connections, including three fan speeds. My current system has a manual fan switch on the wall so all I need ...
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2answers
44 views

Can I replace my furnace's high limit switch with a comparable third-party part?

I have an older Lennox furnace. The high limit switch (#60T15,130F) has gone bad. I haven't been able to find on-line this part number with the exact temp limit specs, and Lennox no longer carries ...
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0answers
41 views

Removing stuck “through the wall” air conditioners

I have two through wall air conditioner units that cannot be removed. These were installed within sleeves in the 1970s and have been sitting there ever since. One budges a little and the other, not at ...
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2answers
99 views

HVAC System Just Installed Yesterday and AC condenser outside is blowing cold ir

HI my just installed ac condenser is blowing cold air out side . when I put my hand over it and move it around most of the air is hot but a portion of it is cold. Is this right ?
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12 views

I would like to view answers and answer questions [migrated]

I would like to view answers (and answer) questions. I have years of experience in construction and HVAC, but little experience with computers. How can I get a few reputation points to do above?
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1answer
1k views

Connected C-Wire to new Smart Thermostat and Furnace board and still no power

I need help. I've been surfing the internet and have had no luck finding answers to my situation so am hoping for some guidance. I've seen other questions here answered but none that suit my ...
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1answer
330 views

Why won't my thermostat control the HVAC anymore after trying to switch thermostats?

I bought a new Nest thermostat which is supposed to be compatible but needs a professional installation (advice that should have been heeded by non-professional electrician me). This is to replace an ...
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2answers
60 views

Aprilaire 700 humidifier not working properly

The fan does not seem to be running. How can I determine what the problem is? I'm not sure if it's the fan, solenoid or the computer board.
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1answer
11 views

Fan runs when in “on” mode, but not when in “auto” mode while in “cool” setting

I have a Rheem RHPL-HM2421JC air handler, a Rheem 1.5 ton heat pump condensing unit, and a comfort control thermostat. The heat and fan worked well over winter. I can also turn the fan mode to "on" ...
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1answer
104 views

Trane furnace pilot wont stay lit

I have a 1983 Trane gas furnace, Model BLU108E936B1, the pilot light went out, I could get it to relight but wont stay on> Changed the thermocouple, same results, Pilot light doesn't look right as I ...
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0answers
45 views

Yellow wire connected to C terminal, blue wire connected to Y terminal at furnace

I'm trying to install a new smart thermostat the requires a C wire. My old thermostat operated on batteries. The pre-existing wiring system of the old thermostat looked normal (ie. red wire to Rc, ...
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1answer
28 views

How do I wire my old 3/4hp 115-120v 50-60Hz HVAC motor to make an exhaust fan?

My old HVAC blower motor has the following wires and I would like to know how to wire them to a typical 110v plug for use as a garage exhaust fan. yellow (N) black (L) yellow/green (ground) black (M1) ...
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19 views

A/C Insulation on Evaporator Unit [closed]

The issue is however the Lining of the A/C Unit inside was found to be Glued to the Sides and bottom which I believe is called the "Pan". The Apartment had an issue of Mold as the A/C was 3 ton unit ...
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1answer
104 views

Hvac fan runs and shuts off in a cycle when in heat mode

I have a Heil hvac model. N44336336GKE100, The system works ok when in cool mode but when in heat mode the outside fan runs for 30 sec then shuts off for 20 sec and continually repeats the cycle. I ...
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1answer
1k views

Can I have a separate thermostat for a wood boiler?

I want to wire a separate thermostat for my outdoor wood boiler so that just the furnace fan will come on without the propane kicking on. This is a Coleman furnace. Is this possible and if so, how ...
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0answers
14 views

Why does my hvac minisplit freeze up?

What would cause a mini split to freeze up? The Freon level is correct and the air flow is good. This is a multi head system (2) one is working properly the other is freezing up.
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12 views

Can I increase the “constant on” speed of my air handler?

I have an American Standard TWE049E13CB air handler with a variable speed blower. The manual has a chart to adjust the dip switches for fan speeds for cooling, heating, fan off delay, and auxilary ...
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1answer
334 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 ...
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2answers
459 views

How to fill / seal in-slab hvac ductwork?

My house is built on a slab. Within the slab are "channels" which act as ducts for the HVAC system. I assume it is partially lined with metal but based on photos from an HVAC-cleaner, it's hard to ...
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1answer
27 views

Run HVAC fan throughout the day for comfort

At my old house, we replaced the HVAC with a high efficiency unit that came with a thermostat that would blow, say, 50% to 70% of the time for air movement to increase comfort level. I'm not sure but ...
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0answers
71 views

How do I connect a honeywell wifi thermostat with no C wire at the furnace?

I purchased a Trane XV90 furnace in 2001 & I'm upgrading the thermostat to a Wi-Fi model. This thermostat needs a wire labeled C from the furnace & of the 4 wires coming from the furnace none ...
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1answer
99 views

Best Way to Heat a Tri Level Home

I have a tri-level home, which is approximately 1600 sq.ft. Presently I have electric baseboard heat, with a pellet stove on the main level. I am looking to upgrade to a better, more centralized ...
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1answer
35 views

Aprilaire 560 repair

My Aprilaire 560 humidifier will do a bang click many times before it turns the blower on. I replaced the solenoid valve with a new factory part and it still does the same thing. What next?
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1answer
65 views

Central Air Unit not Sending Enough Power to Thermostat

Right now I don't have specifics on my central air unit (make, model, etc) but hopefully the info I provide will help. I have a Second Generation (and Third Generation) Nest Thermostat hooked up to ...
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1answer
39 views

What is the difference between the coolness of different wall types in hot weather

Given a 30cmx30cm concrete beam and pier structure, with infill, and year-round (equatorial) daily temperatures of around 25C-33C, with around 80% humidity. What is the difference between these ...
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5answers
11k 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 ...
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3answers
3k views

How can I heat up my apartment to kill bedbugs in Southeast Asia?

I have a bedbug problem in my apartment and I want to fix it myself with heat. (I do not want chemicals sprayed around.) Apparently, getting a room to 140 degrees for two hours is sufficient to kill ...
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0answers
26 views

Improving air flow using supply and return exhaust fan with split type air condition

I have slight issue with uneven temperatures between two rooms. Say we have two rooms, Room 1 (cold room with AC) and Room 2( without AC, hotter room). Room 2 is ventilated by Room 1 AC by opening ...