Questions tagged [hvac]

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

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1answer
32 views

Replacing A/C thermostat

I think that my mother has a bad thermostat. When the A/C is turned on, the furnace blower works but not the outside unit. However, when I press the contact switch (outside), both the compressor and ...
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1answer
92 views

Two HVAC units on one condensate drain line

I am renting a house with two HVAC units - one upstairs and one downstairs. There were two condensate drain lines (one per unit). The units were older so when they quit working efficiently the ...
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1answer
31 views

Blower Motor Heat and Cool Control Board

I’m an electrician by trade but i have a friend who needed his blower motor replaced. The parts store sold him a motor but it only has one hot leg. The control board has a hot for cooling and a hot ...
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33 views

Installed Honeywell R8285A 1048 control center combined with a Honeywell PRO 8000 thermostat

to operate an inline duct fan on a long run to a new addition. Thermostat in the new addition activates fan when the thermostat is set to cooling perfectly. I can use it to manually turn on the fan. ...
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1answer
52 views

Where to install C wire?

I need to run new thermostat wire since I don't have a C wire to power my smart thermostat, but need some guidance on where to hook it up. I have five wires at my thermostat, two going back to my ...
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2answers
109 views

I have an unused C wire hooked up to thermostat and have no idea where to connect it to the furnace for power

I know this question gets asked all the time but I've spent hours staring at forums as well as my furnace and at this point I'm desperate. I just bought a nest thermostat that needs a C wire ...
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1answer
62 views

HVAC blower fan won't stop

FINAL UPDATE: I have found the culprit - the Nest thermostat itself. First, I disconnected the t'stat at the control panel and found out that the fan would no longer start upon powering the system. ...
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1answer
141 views

Need to identify wires coming from external AC Unit

idiot DIY'er here :P. I recently installed a smart thermostat and long story short; I removed the two wires from my furnace's board for the external air conditioning unit in the process. I was going ...
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2answers
43 views

a/c doesn't turn on when temperature is reached

I just changed my thermostat and it does the same thing [as the old thermostat did?]. I get up in a.m. thermostat is set at 77 F. When inside room temp reading on the thermostat reaches 77, a/c doesn'...
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1answer
61 views

Cutting 4" hole on Rim Joist

Would it be advisable to cut a 4" hole on the basement rim joist to install a bathroom fan. The joist size is 8" and is supported by a basement wall.
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1answer
50 views

Remove switch that controls thermostat

I recently bought a condominium in a large building, built in 2005. It has a single thermostat, and the thermostat works fine. But right next to the thermostat, there is a switch. It looks like an ...
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1answer
36 views

a/c condensation line not draining

I have a unit that is installed in the attic and is about 2 years old. For the first year everything was fine and then one day it wouldn’t run. So I hooked up the shopvac and sucked the condensation ...
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16 views

Ac unit blower cuts on off on off

My blower fan cut on off on off on off that fast then it stays on and runs fine. Only dose it at the beginning of the cycle
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0answers
18 views

Name of A/C hose fitting

I have a set of R134A manifold gauges that I would like to use to pull a vacuum on an R410A system. My hoses terminate at the R134A quick connector with the threading on the right of the attached ...
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1answer
34 views

Old furnace with extra wire, but no c terminal Janitrol, 19 year old furnace

I've searched multiple threads regarding this, but I didn't manage to find any that seemed to match my use case. My board doesnt have a C terminal, and it doesn't have the other terminals connect to ...
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25 views

How do I plug an old duct

While renovating my kitchen, I came across an old exhaust duct in the wall. It goes through the chimney bricks and into the interior of the chimney. The boiler uses a duct within the chimney that is ...
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1answer
64 views

Overflow line tied with Condensate Line

had a house inspection done and the inspector told that Irregular materials were used, I am attaching a pic. how much work is it to repair it? is it a easy fix? Thank you
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1answer
39 views

Can I safely jumper between either G or Y and RC at thermostat panel to troubleshoot AC problem?

I'm trying to troubleshoot a non-functioning AC. The fan does not come on and there is no cool air/condenser does not run. My thermostat is a Braeburn. Three things I'd like to try for ...
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0answers
44 views

AC unit not turning on

My A/C doesn't come on when I set the temperature on the Braeburn thermostat very low. Also, the recirculation fan doesn't come on when I set the thermostats fan setting to 'on', as though the indoor ...
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60 views

Is this where my HVAC air filter goes?

I moved into a home that was poorly taken care of by the homeowner before. It dawned on me today that I've never replaced the HVAC filter (I guess I'm bad at taking care of the house too :) ) in the ...
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1answer
48 views

Furnace with no “C” connection

I have a mobile home furnace. This furnace only has a 4 wire connection terminal, G,W,R,Y. I also have a condensing unit outside with the 24 volt 2 wires coming to the furnace. I know I connect one to ...
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0answers
40 views

Is one large whole house fan better than two smaller ones?

I'm having an addition put on my house and I'm considering the "Quiet Cool" line of whole house fans. The fans are quite expensive and price wise two small fans are almost the same price as one ...
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5answers
75 views

How to size a whole house fan?

I'm in the middle of a home addition and am thinking about adding a whole house fan. The finished size of the house will be about 2000 square feet - approx 1500 on the main level, and 500 on a lower ...
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20 views

HoneyWell baseboard thermostat

Hello everyone! Need some help here (trying to help a family member) They recently purchased a home that has a furnace and AC ( with central air) in each room there at these honeywell thermostats. ...
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1answer
37 views

Why doesn't my HVAC system use the away temperature setting?

I have a Carrier Infinity dual-fuel 5 stage HP w furnace. I set the away temp much lower than the home temp but the HP keeps running to bring the temp up to the next home temp. I would think the ...
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16 views

Lennox Furnace Troubleshoot Assist

I have a Lennox Elite G50UH-24A-070-15. It quit entirely and threw the error "Pressure Switch open or blocked" according to the diagnostics panel on the front. Recent renos so thought it was clogged/...
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1answer
37 views

How should I support rectangular duct in wall?

In California, I'm installing a 3x14 rectangular supply duct from my attic to my first floor. It goes vertically through the second floor wall, through the floor, and ends in the first floor ceiling. ...
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0answers
23 views

Draft Inducer Takes a Long Time to Start

When I turn the thermostat up I hear the draft inducer relay click, but the inducer motor doesn't start immediately like it used to. There's quite a lag time before I hear the draft inducer fan start ...
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1answer
120 views

Converting I+ I- thermostat to 'standard' wiring

I've been replacing my thermostats with the RadioThermostat CT50, which reports to my home-brew home control/alarm system. I have a 3-year old AireEase 4-ton unit in the shop that has a Comfort Sync ...
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0answers
34 views

AC Goodman unit not powering on

Is getting hot and I tried to power on my AC unit, it only blows warm air and no sound from unit outside, fan is not moving, no noise. Checked indoor fuses were on and reset them Checked outdoor fuse ...
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1answer
98 views

convert a onan 110v generator to 220v

My RV has roof-top air conditioning units. The generator will run 2 units. I would like to convert the RV to a mini-split system with 2 air handlers. They require 220V, and draw 25 amps; however my ...
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6answers
4k views

Is Electric Central Heating worth it if using Solar Panels?

I understand that electric heating is less efficient and comparatively more expensive than gas heating (propane or natural gas), but considering I live in Texas (a lot of sunlight) and I intend to ...
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1answer
21 views

Furnace burners shut off an hour after running?

Older furance that wasnt holding pressure. Leak was found and gas valve replaced. Gas is on. Fired it up yesterday for the 1st time. The house has been vacant awhile. We had no problem. Came ...
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1answer
57 views

A/C blower does not work after a power surge

My outside unit works but my inside unit does nit turn on, its a bryant a/c system. On the unit it says the circuit board is built into the blower motor. The transformer buzzes. Can I replace the ...
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18 views

Furnace limit switch only reading 12 volts, I have 24 volts coming out of transformer

12 volts at primary limit switch, 24 volts out at transformer 24 volts at c & w terminals when stat calling for heat. furnace will not light, trouble codes call for bad primary/secondary limit ...
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1answer
49 views

C Wire in Air Handler

Can someone please help me find where to connect a C wire for my smart thermostat? Here are some pictures with descriptions. It is difficult to get to the 24v connection in the back. My schematic ...
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0answers
24 views

Circulating main floor AC to above and below floors

In the summer the main floor with the AC is always comfortable, the basement is a bit warmer and the 2nd floor unbearably hot. I'll be adding more insulation under the roof to help, but short of ...
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1answer
155 views

What is this mysterious filter and purpose?

Behind the regular HVAC air filter and next to the duct, there is a filter area with some rough filter covering an additional smaller duct. Does anyone have any idea what it is and its purpose?
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1answer
48 views

Insulating built-in air conditioners

My apartment has Frigidaire built-in air conditioner holders. I did not buy a Frigidaire AC unit because the size needed to perfectly fit the holder was unnecessarily large (and expensive). I have a ...
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0answers
18 views

HVAC: attic heat loss

Should a ventilated attic (w. Openings in the eaves) be warm in the middle of a cold winter that has a heat pump installed as the heating system for the living area below. If it is warm does that mean ...
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2answers
36 views

4 ton air handler with 3.5 ton air conditioner

What effect will having a 3.5 ton air conditioner used with a 4 ton air handler have on the energy efficiency of the hvac system? Right now we seem to be using a lot of energy per month. The question ...
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0answers
19 views

Air return proximity to furnance

We are refinishing our basement that wasn't original conditioned. New supplies and zoning were added by a contractor. We want to add an air return in the living space by tapping into the main return ...
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0answers
15 views

Name of my central heat pump unit

This sounds crazy but i cant find out what brand central package unit i have. Ive looked everywhere on the internet.. I believe its a york , because there is a address on the bottom of this tag saìys ...
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1answer
21 views

Upgated pump for 10 zones, 3 floor house?

I currently have a tanco (I don't have the current model # now) in a 5 zone 2 story house. I was recommended to upgrade to a tanco 0010-F3-1IFC bc I am adding 5 more zones, and 2 zones will go up to ...
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1answer
40 views

A.c. fan outside not coming on

It started with the thermostat not going in on only fan. That night i go to turn the AC on and the condenser fan wouldn't come on so I took a stick moved the blades and it started . i thought its the ...
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2answers
100 views

HVAC fan on compressor not coming on

I noticed today that the button on the thermostat isn't turning the fan on by itself. I tried today just to turn on the fan couldn't get it turn on. Tonight we turn on the AC couldn't get cold air. ...
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1answer
12 views

Heat pump filter

I have a trane heat pump in my attic, do I replace the filter in the air handler AND return grill? Not sure if I can use just the return grill which is in my hallway ceiling
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1answer
33 views

How should I size an air conditioner for a room in the attic?

My bedroom is upstairs in the attic and much of the interior walls/ceiling are the underside of the roof. I believe there is a couple inches of hard foam between the drywall and the sheathing/roofing....
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2answers
42 views

What is the difference between the filter on my furnace and an Air Exchanger?

I live in the Pacific Northwest (Seattle area) and the allergy season has started for me. It is so bad that I am thinking about getting an air exchanger for next year. The house I live in was built in ...
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2answers
107 views

HVAC Heat Supply - Register type (Square Register or Round Diffuser?)

We are adding new heat supply runs to our basement ceiling. We have had 3 HVAC contractors look at it and all 3 want to use 5" round air diffusers instead of the normal metal square registers. Here ...