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

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6
votes
9answers
30k views

How can I prevent my HVAC condensate drain line from freezing?

Last night, my heat (forced air) suddenly stopped. Today, a plumber figured out that my heater is 90% efficient, produces lots of condensate, and the drain line had frozen. We went outside and saw ...
2
votes
1answer
126 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 ...
0
votes
1answer
83 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 ...
1
vote
3answers
442 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 ...
1
vote
2answers
241 views

HVAC contactor sparks when AC kicks?

The HVAC and control board is a McQuay Mark IV. I'm not sure if I would like to try and fix this myself yet. Just trying to figure out the issue before deciding where to go. Here's the scenario: ...
0
votes
1answer
56 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?
0
votes
0answers
48 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 ...
1
vote
1answer
104 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?
0
votes
1answer
244 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 ...
1
vote
0answers
28 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 ...
0
votes
0answers
37 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 ...
1
vote
1answer
882 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 ...
-1
votes
1answer
126 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 ...
0
votes
1answer
40 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 ...
4
votes
2answers
213 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 ...
1
vote
1answer
221 views

Why does my shower run out of hot water quickly?

My shower runs out of hot water quickly. Initially the water is perfectly hot, then it starts cooling after a minute or so and we need to adjust the lever to maintain the temperature. Somewhere around ...
1
vote
5answers
4k views

How to fit 4" rigid aluminum duct vent in between walls when there is an angle brace?

I want to do what these people have done here: The problem is I have bracing going diagonally and it is not leaving enough space for the 4" aluminum duct vent. Can I saw the bracing off for the ...
1
vote
0answers
44 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?
12
votes
4answers
171k views

What's the most common cause of A/C refrigerant lines freezing?

I noticed my house wasn't getting under 75°F this weekend when I had the thermostat set for 70°F. Since I'd done a lot of drywall sanding inside recently, my first idea was to replace the filthy air ...
0
votes
2answers
130 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 ...
0
votes
1answer
243 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 ...
1
vote
1answer
54 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 ...
0
votes
0answers
28 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 ...
1
vote
1answer
2k 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 ...
44
votes
4answers
203k views

How can I add a “C” wire to my thermostat?

So, the spiffy new wi-fi thermostats want power on the C wire from thermostat, but the old thermostat doesn't have a C wire at it. What's the easiest way to add the C wire/24 volt to the thermostat ...
1
vote
2answers
112 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 ...
0
votes
0answers
20 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 ...
0
votes
0answers
36 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 ...
0
votes
0answers
16 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 ...
3
votes
1answer
98 views

Should I be worried if my A/C ran with the cover on?

My wife accidentally switched on the "cool " mode and the a/c was activated, however the cover was still on the unit outside. Ran like this for about 2 hours. I noticed it and turned it off and went ...
0
votes
0answers
62 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 ...
1
vote
1answer
100 views

Damper close to main supply vs damper close to the register end: what is the difference between the two positions?

For the air duct that feeds a room, what is the difference between installing a damper at the register end and installing a damper close to the main supply duct?
0
votes
0answers
62 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 ...
0
votes
3answers
117 views

Why does the outside fan stop but the blower fan continues to run?

We can have the thermostat set on 76 but wont stay 76 in house. Will come on when temperature is 79 in the house.
0
votes
1answer
542 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 ...
0
votes
0answers
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 ...
1
vote
0answers
56 views

Can I remove HVAC pipes after exposing the ceiling?

I recently removed the drywall ceiling from my basement and have two related questions about removing the HVAC ducts/pipes. Pictures attached here: http://imgur.com/a/qep4w 1. Is it OK to remove the ...
2
votes
2answers
2k views

What can cause an A/C to freeze up

Our A/C evaporator coil freeze up last year, so I called out a technician. He said that it was charged with the proper amount of Freon, and my problem [paraphrased] "something had narrowed the inside ...
0
votes
0answers
155 views

Why would my AC turn on and off randomly?

My AC unit turns on and off randomly regardless of whether the thermostat is set on or off. I've even tried removing the batteries. Does anyone know why this might happen?
0
votes
1answer
48 views

Allergies and an economizer

I had an economizer added to my HVAC system last fall, which is fantastic for cooling my second floor down in the evenings during the shoulder seasons where the weather is cool in the late afternoon ...
1
vote
0answers
83 views

How can I use a portable A/C unit to cool my clean room?

So, I have built a room inside my shop, a clean room for finish and airbrushing. I want to cool this room as I spend more time in it than the rest of my shop (garage) So, I get a portable unit. ...
1
vote
0answers
35 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 ...
2
votes
2answers
294 views

Should I convert from a rooftop to a split HVAC system?

We have a packaged HVAC on the roof and the AC needs to be replaced. It's 23 years old and dying/dead. We were considering buying just an AC and keeping the package unit running for heat. We feel ...
1
vote
2answers
58 views

Is having a branch off the end of main heating HVAC duct bad and if so, why?

Question: Is having a branch off the end of main heating HVAC duct bad and if so, why? Background: A heating and cooling contractor sales representative came to my home today. He saw the situation ...
0
votes
4answers
4k views

How can I modify a 4 wire thermostat to a new thermostat requiring c wire?

I attempted to replace my thermostat with a fancy new Trane z-wave enabled model. To my dismay my home was only wired with a 4 wire setup with no 5 hidden in the bundle. I followed Insx on the web ...
1
vote
3answers
133 views

How to hide AC lines up against brick siding

I had this AC system installed, and didn't realize when asked about what location i'd prefer the compressor that it would look so ugly having it off the corner of the building instead of in the middle ...
1
vote
1answer
75 views

HVAC replacement

we just recently purchased an older home- 1978 - 2200 sqft, 2 stories, 2 14x20 returns - one downstairs, one upstairs, 5 ton 10 seer system, 10yr old goodman air handler but the condensor is unkown ...
15
votes
10answers
19k views

Do thermostat-controlled, auto-adjust HVAC vents exist?

The residential forced-air HVAC systems I have seen are controlled by a single thermostat in one room. One has to manually adjust the vents in order to adjust the temperature in other rooms. Is ...
1
vote
2answers
1k views

Furnace blower motor won't turn off

I've replaced both limit switches on my Comfortmaker furnace plus the control board. Blower continues to run and the unit will still heat my home. Component changeouts did not make a difference in ...
3
votes
2answers
4k views

$400 electric bill traced to heater - what could be wrong with it?

Back in December/January, we got a real shocker; a $400+ electric bill. I thought there must be a billing error, so I went out to the meter, and found that not only was the number probably right, we'd ...