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

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What is causing this air-conditioning unit to cool on cold days?

This is a temperature log from a reverse cycle air conditioning system that has run fine for getting on for 30 years. It has suddenly started to blast out cold air on days when it should be heating. ...
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12 views

how to install a casement window ac unit in a standard horizontal window?

Ok... I have scoured the internet. I was given 2 casement window ac units. Both of my heat pumps were stolen and this is an army wife turned widow make do type situation for while I save to replace ...
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1answer
49 views

Is installing a packaged HVAC unit (PTAC) a realistic DIY project?

I'm a handy guy and can do pretty much anything around the house that I put my mind to. Assuming I can handle the part of the install that is outside (the concrete pad, the hole in the crawlspace ...
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23 views

Issues after capacitor replaced on AC unite

Had a checkup on my AC/ furnace a couple weeks ago. The technician said the capacitor leaking oil and not pulling enough amps. He recommended me getting a whole new system. (my house built 6 yrs ago) ...
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15 views

Single Stage or 2 stage furnace

Just bought a house that has a furnace on last legs. House is 1941 masonry (Chicago). 3 floors: finished basement, first floor, 2nd floor (converted attic with vaulted ceilings and way too hot). Total ...
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1answer
25 views

Hot 2nd floor converted attic master suite

Just bought a 1940's masonry construction house. House has a finished basement (cold as a meat locker), first floor (comfortable) and 2nd floor (too hot). The 2nd floor is an attic that has been ...
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2answers
74 views

Do I need a neutral wire when connecting a 240V device?

So this is still not very clear to me: I am trying to get 240V to an appliance that does not need a plug (direct wiring), I won't need a neutral wire, is this right? In fact there is nowhere to ...
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2answers
81 views

No AC. I have a few HVAC troubleshooting questions

I'm having issues with my AC. Basically, the symptom is that I feel cold air coming out of the vent, but it has no pressure, almost like I have to put my hand IN THE VENT COVER to feel any cold air. ...
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1answer
16 views

ecobee3 Installation - Thermostat Y Terminal (yellow) Wire Connects to C Terminal Board

enter image description hereI'm attempting to install a new ecobee3 on an older Coleman Evcon gas furnace and AC HVAC system. The system is what I would consider typical residential as far as I can ...
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25 views

My A/C Unit stopped working after replacing blower motor

Any idea what I may have done wrong here or how to check? I replaced my blower motor (it was 100% compatible and had the proper capactitor), and upon starting it up the blower did nothing and the ...
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16 views

Should I install a doorway fan or dehumidifier?

I have central air in a rancher (one floor), and the living room is on one end of the house. That room is on a slab, and has always been noticeably hotter in the summer and colder in the winter than ...
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40 views

lennox AC condenser Fan running backwards

I have been trying to figure this out for a little while and about to check into the nutty house!! The Condenser fan went bad in my AC Unit. It was a 3 wire motor. I got a Universal replacment motor ...
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1answer
110 views

AC unit won't turn on: both inside blower fan and outside fan unit won't turn on

AC unit won't turn on: both inside blower fan and outside fan unit won't turn on. It is as if I had gone to the circuit breaker and cut the power to the whole HVAC system, but I didn't. I've been ...
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21 views

Residential HVAC: one main thermostat, what do the other thermostats in the rooms do?

Are the other thermostats only meant for non-force air heat only? Does it mean only one thermostat in the house needs to have both heating and cooling, and auto or fan-only switches? It sure make ...
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2answers
154 views

WIFI thermostat no C wire

I hooked up a Honeywell WiFi thermostat last fall. There is no C wire in the furnace & the Honeywell rep suggested I wire up a small separate transformer with new wires going to the C and RC ...
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39 views

replacing single pole York A/C contactor

I am trying to replace a single pole contactor with burned contacts on York package unit Model D3YS030N064069. The old contactor has four 24 volt lugs on one side. The new contactor has 2 on each ...
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1answer
41 views

central a/c won't cool

My A/C unit was just checked last week- the tech said it had enough freon. Monday we had a nasty storm- electricity flickered, but never went out. After the storm, we noticed the a/c went on, but it ...
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1answer
65 views

Is my AC right-sized for my house

2 years ago I had a Bryant 2 Ton 13 Seer Air Conditioner + new furnace and coils installed in my 2800 sqft ranch style house with 6 bedrooms and 2 baths split evenly between the basement and main ...
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3answers
62 views

A/C not keeping up

So, the first warm-ish day of summer finally showed up in the Black Hills yesterday and I noticed that our central air conditioning was not really keeping up... the thermostat was set at 72, but the ...
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2answers
74 views

Is it economically reasonable to cool the roof by water evaporation

I want to estimate the outcome before going into hassle of installing the sprinklers/mist emitters. I have a place on the last floor, you can call it an attic, directly under a flat roof which is ...
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1answer
34 views

Bring HVAC Ducts to the Ground?

I'm finishing my basement. Is there any benefit to bringing the vents from the basement ceiling to the ground after I finish framing?
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2answers
51 views

Why does my furnace run periodically when the thermostat is off?

I just moved into a small apartment that has oil tank / water baseboard heaters. At first the furnace would not come on at all, after hearing the "click" in the thermostat. Maintenence was sent 3 ...
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1answer
71 views

What are the two pipes coming out of the back of my outside air conditioner?

On the back of my air conditioner there are two pipes: One is covered with insulation and one is bare pipe. What is the purpose of these pipes?
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29 views

Changing Trane Baystat240a to another thermostat

I want to change my current thermostat to a programmable electric one (no batteries). Could someone verify if it does have a common wire and if all wiring could fit modern thermostats? Looking at the ...
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1answer
136 views

Need to know where to connect my C wire [duplicate]

I had the extra wire in the wires run from my thermostat to my A/C, but the old thermostat did not need the C wire, so it was cut and stuff on both ends. While installing the new thermostat I ...
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1answer
18 views

Why “W” (heat contactor) and “E” Aux Heat connected in Thermostat

I'm trying to update my thermostat to one that has a scheduling feature. My plan is to just copy how it was hooked up in an old 129N Thermostat from Armstrong however, I can't figure out why the "W" ...
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25 views

How much refrigerant in an average 12 cu. feet freezer?

How much refrigerant goes into a 12 cu.ft chest freezer? On the nameplate it says ______POUNDS ___16___OZ (nothing written in front of pounds) is there really only 16 ounces of refrigerant in those ...
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1answer
62 views

When is a variable-speed compressor HVAC unit worth the cost?

Surprise, its summer and our AC broke down. We were quoted prices for installation of the current standard (SEER 14) AC units (about $6500 unit cost and installation) vs Trane's SEER 18 AC units ...
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2answers
124 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 ...
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1answer
144 views

Troubleshoot AC issue, no inside blower

I need help troubleshooting Rheem RAHE-036JAS, Armstrong G1N80AU125D20C-1, Honeywell ST9160B 1068 Board, Honeywell SV9520H 8034 Gas Valve. About a week ago, AC and Heat were working fine. After ...
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1answer
35 views

Difference in total pressure when HVAC system is on or off

This is a follow up question to one that I asked here. I am measuring the total pressure at the registers (all registers are open) with the BMP180 pressure sensor and somehow they don't change very ...
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27 views

Help AC question

We purchased a home last year, at one time it was zoned with separate AC units upstairs and down. Well a past owner took out the upstairs unit but left the blower in the attic, there is duct work ...
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19 views

A/C still blows when unit is off.

Our A/C is turned off but we still get cold air coming out of the vent diffusers. This is from our downstairs unit. Is that a problem?
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2answers
193 views

Who do I hire to design my home HVAC system?

Preface I need to buy a new HVAC system for my 1930s home. I currently have forced air duct system. My gas furnace was installed in 1985 and is rusting out, and I'm not sure about the air ...
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2answers
61 views

How to repair pierced refrigerant line in chest freezer?

My idiot friend was screwing brackets inside an ice cream freezer with self-tapping screws, and one of the screws pierced a copper line containing refrigerant. Apparently it made a crazy hissing sound ...
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1answer
92 views

Duct static pressure vs ambient air pressure

I've read that air handlers are typically rated for 0.5 iwc. Doing a simple conversion, this comes out to about 125 Pa. Is this with reference to the ambient air pressure? So, if I had an absolute ...
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1answer
35 views

Can I move an attic furnace downstairs

I love the single unit HVACs. I hate the unit in the attic - it has leaked so many times. Now that I am ready to replace the attic unit, I was wondering if I could have the same setup as my 1st floor ...
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24 views

HVAC 3A fuse shorting on cool

I recently came back from a trip, and the thermostat was still working. On turning the AC on, the wall-powered thermostat decided to die. Upon investigating in the attic, I noticed the 3A fuse had ...
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1answer
128 views

A/C Air Handler Leaking Water Everywhere

I have a relatively old air handler that has worked fine for many years. Just recently, it started leaking water everywhere, and it seems to be seeping from inside the base of the air handler itself ...
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2answers
71 views

Can I pump down an Air Conditioner myself?

We are planning on having a new concrete patio poured in a couple of weeks and need to move our AC unit to make way for the slab. Is it possible for a layman to pump down the coolant and move the ...
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0answers
14 views

Can I add another heat run to my furnace?

I'm looking to add a bedroom to the basement and would like to add a heat run to the new room (return air will occur through an opening between the ceiling joists). This seems easy enough, but I ...
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1answer
73 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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24 views

How to fix uneven central heating and air?

My central heating and air conditioning system does not heat my home evenly. Half of the house gets significantly warmer / cooler than the other half. I have tried adjusting the registers, but to no ...
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0answers
14 views

Will a Carrier heat pump generate hot air in the heat mode if the compressor is bad?

The heat pump works ok in putting out heat, but puts out hot air in ac mode as well. Had an hvac tech look at it. He replaced the capacitor and said the compressor was bad. Can the heat pump put ...
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41 views

Adding dual zone capability to an existing HVAC system in a house with existing 2 zone manual ducting

I have a house that has existing dual zone ductwork in place (separate ductwork for the upstairs and downstairs) that has manual dampers. I recently replaced the HVAC system with a new geothermal unit ...
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1answer
64 views

Can't get my AC to turn on at all

Recently our AC stopped working. The thermostat is working properly, but the unit just started blowing hot air. I've never worked on a AC before, but I was trying to save some money. Anyway started ...
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37 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 ...
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37 views

Troubleshooting pressure error code for Trane XV80

I have a ~7 year old Trane XV80. Recently, it started throwing up the pressure error code (3 flashes). Inducer fan would start, but the burners wouldn't light. Being lazy, I would basically power ...
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1answer
245 views

Can I connect two wires to a single screw terminal in my HVAC system?

I am installing a new honeywell WiFi thermostat but the old battery operated thermostat had batteries and no "C" wire. I look at both the thermostat and the air handler and found an extra un-used blue ...
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5 views

No “C” terminal on Trane air handler [duplicate]

I am installing a new honeywell WiFi thermostat but the old battery operated thermostat had batteries and no "C" wire. I look at both the thermostat and the air handler and found an extra un-used blue ...