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

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3answers
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What's the most cost effective way of ventilation automation given no prior knowledge in the field

I have 3 fans for air inflow, and 3 fans for extract, all in one big hall. Currently I set the power of their motors with dimmers myself, looking at CO2 and temperature readings. I want to replace ...
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1answer
136 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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1answer
222 views

Why would only 1/3 of my registers be blowing warm air?

I have a Coleman gas furnace in a wall space in my house which somehow shares the blower on my a/c unit on the roof because it turns on when furnace is called to start, though it does bump up after a ...
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1answer
48 views

Could a leaking boiler be fixed?

I'm having a leaking hole in the cast iron boiler tube so does it mean that its time for a new boiler or is there any way it could be permanently fixed?
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1answer
25 views

My Air conditioner suddenly became defective after a power outage

So, these are the symptoms: 1] The big fan outside is taking a lot longer to start. 2] Within 2 minutes of start-up and cooling, it makes a growling/ rattling sound and 3] The power switch to start ...
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1answer
27 views

Can AC fan or motor be upgraded?

My AC blows cold air, so I assume my compressor outside works OK. Please correct if that's an incorrect assumption. The problem is, there is very little cold airflow that comes out of the floor ducts....
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2answers
155 views

How can I determine what grade air filter is appropriate?

I'm trying to figure out what kind of air filter is appropriate for my house. My local home warehouse store stocks over a dozen options. The primary difference between them seems to be Microparticle ...
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1answer
131 views

How to connect thermostat to newly-installed condenser/evaporator unit

I installed a furnace evaporator and condenser brand goodman 4 ton unit but need to know how to connect thermostat from condenser to the furnace to the thermostat if any suggestion.
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2answers
3k views

Can I attach a HEPA filter to the HVAC outlet?

I am currently living in China and want to improve the indoor air-quality. We have a Hitachi R410A HVAC. All the room in the house are controlled separately. Just to make it clear up front, I am not a ...
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1answer
79 views

Can you increase the speed of an ECM AC blower?

I have a Trane XV95_060 for furnace and Trane XR15-018 for AC I would like to know if the speed of the blower can be adjusted (increased) Before I had a 1ton AC and that was all right for the house ...
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1answer
54 views

My master bedroom is hot! Should I install a return in my master bedroom?

Thanks for taking the time to read my question. I have a house where the master bedroom was added in during an expansion. The master sits half above unfinished basement and half above crawlspace and ...
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1answer
24 views

AC tripping power breaker

My central AC is dripping power breaker What I have checked Filters are clean I cleaned outside unit with water I put in a new capacitor It cools fine it just trips middle of night like 4am
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1answer
271 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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5answers
48k views

How much cooling can I expect from a central air conditioner?

Yesterday's high was 106.0F, low of 79.2F, full sun all day. AC set at 78F, indoor temperature reached about 85F. Today's high was 105.4F, low of 81.1F, full sun all day, now about 102 at 7pm. AC ...
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1answer
40 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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0answers
42 views

High Power Bills Related to Air Conditioner

So I seem to be having trouble with my power bills (they've often been near $400 while other people in my area with a similar sized house usually get around $140), and I've isolated the issue to my ...
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1answer
44 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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1answer
77 views

HVAC - Circuit Board Fuse blows on AC Switch

I have a Honeywell System. Back in November of 2014, I replaced the Circuit Board with one by Honeywell from Amazon (1014460). The blower motor was replaced over 2 years ago. Last month, I have ...
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1answer
36 views

My AC unit won't blow cold

So, I was changing a light switch and flipping circuit breakers to find the correct one. I accidentally flipped my AC circuit breaker off and then back on. After this I noticed the AC wasn't blowing ...
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2answers
35 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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0answers
22 views

Should drip pan be replaced with install of new furnace?

We just purchased our first home; part of the agreement of purchase was that the previous owners had to install a new furnace which was done by a professional installer from a reputable company in the ...
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2answers
51 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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1answer
182 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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1answer
62 views

Is it necessary to discharge the capacitors on an AC condensor?

I intend to replace the capacitors on my house air conditioner condenser. This video claims that discharging the capacitors is not necessary, because the circuitry will discharge through the fan ...
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2answers
47 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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6answers
7k views

How do outdoor mist-cooling A\C units fare in real-world usage?

I live in Phoenix where summer outdoor temperatures regularly exceed 110°F and humidity around 15% or lower is not uncommon. In this environment a mist system can easily pull the temperature down ...
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1answer
23 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
294 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
105 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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1answer
354 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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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 issue so ...
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1answer
24 views

Honeywell VR8300A3500 Single Stage Heat Gas Valve to Ecobee3 with C wire

Hey everyone have a quick question regarding a honeywell VR8300A3500 Single Stage Heat Gas Valve and the introduction of a Ecobee3 wifi enabled thermostat with a "C" wire. just want to make sure i am ...
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2answers
64 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
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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1answer
106 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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1answer
28 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
46 views

Water dripping out of small pvc pipe in soffit of house

Yesterday was an extremely hot day here in SoCal with temperatures around 100F. The AC unit had been turned off during the daytime and at nighttime we turned it on to cool down the house. A few ...
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0answers
189 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
29 views

A/C freezing damaged air handler blower?

While I was moving, I left my front door open for at least two hours. As a result, my coils froze up outside and inside the return and the inside handler. The vents were not putting out any air and it ...
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1answer
111 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
353 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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3answers
8k views

Is it possible to use my window A/C unit without actually installing it in the wall?

So, here's the dilemma. I want to install a window unit in my garage. I know how to do this, but my wife isn't supportive of the idea because we are trying to sell the house currently. Anyways, ...
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3answers
141 views

How to recharge a window unit air conditioner?

Can I recharge my window unit air conditioner or do I have to send it to a specialist? The AC unit that I have is about 15 years old (nothing lasts forever)... and I happen to have about 20 lbs of ...
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2answers
521 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
42 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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1answer
23 views

Air handler blower, motor, or something else?

My blower just stopped working. I have 240 volts to the motor but it won't spin. It will turn an inch or so but that's it and it tries repeatedly. Could it be something besides the blower or the motor?...
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1answer
20 views

HVAC thermostat current

What is the typical current (in mA) carried by the 24v thermostat HVAC wire bundle in a typical low voltage application? I'm using 18/7 wire.
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0answers
23 views

Carrier Central Air Conditioner Model 38CKC042-340 with 35/5 instead of 40/5

I have this unit Carrier Central Air Conditioner Model 38CKC042-340 I was looking at http://www.repairclinic.com/Shop-For-Parts/a41b370d1182307/Model-38CKC042340-Carrier-Central-Air-Conditioner-...
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1answer
128 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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2answers
61 views

How to move from RH/RC thermostat to C thermostat in AC only system?

I see this is a pretty common question, but the answer seems like it might be dependent on your thermostat and air handler, so I'm posting with my specific questions. I'm upgrading from a White ...