Tagged Questions

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

learn more… | top users | synonyms

1
vote
1answer
743 views

How to diagnose a broken Aprilaire humidifier (Model 600)?

I have an Aprilaire Humidifier Model 600 (or maybe 600M) mounted on my furnace. The humidifier is not turning on (i.e. letting water flow over the filter) when the furnace is on. The below images ...
4
votes
2answers
6k views

How do I identify the C terminal on my HVAC?

How do I identify the C terminal on an HVAC, furnace, or boiler? If the terminals don't have a screw labeled C what should I look for on the wiring diagram? What steps should I take if a wiring ...
3
votes
2answers
671 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 ...
2
votes
1answer
968 views

What can I use to adequately insulate round rigid metal ducts?

I'm installing properly sealed round metal ducts in my unconditioned attic for heating and cooling. I've probably got 100' total of 6" duct to cover. I'm trying to achieve an R-8 insulation value, ...
1
vote
2answers
225 views

How do I close this hole in the HVAC vent?

What's the best way to close up this hole in the venting leaving the hvac? Would foil tape be sufficient? Right now it bleeds out hot air into the basement in the winter, and cold air in the summer. ...
1
vote
0answers
718 views

How can I tell if my bathroom ceiling vent is working properly?

Seems to take the vent forever to clear shower vapor from room. I purchased a vent that had a good rating. It is vented to the outside. How do I know if it is working properly and actually venting to ...
4
votes
3answers
2k views

Why is my gas furnace vibrating when blowing hot air but not when blowing cold air?

I have a gas furnace. I recently replaced a bad blower motor. At that time I also cleaned out the blower housing and squirrel cage. The AC runs fine with no vibrations or any symptoms of an off ...
3
votes
2answers
539 views

How can I calculate the Btus needed for a single room A/C unit?

How many Btus is recommended for a room about 35 square meters? I have 2 units with 13,000 Btus each. I'm thinking it should be enough, but the room is just so-so cool. I can never say it's COLD in ...
1
vote
4answers
1k views

How can I calculate the power consumption of an A/C unit?

I have an AC unit with the following specs: Cooling Capacity: 1260 kcal/h, 1.47kW, 5000 Btu/h Fan Motor Power: 0.034 kW Current: 0.155 A My question is how much power does this unit actually ...
4
votes
1answer
2k views

Is flexible gas pipe safe to use for main or long runs?

The house we purchased is a "tear-down". A builder bought the older structure, partially tore it down and built a bigger house on the old footprint. A lot of the original gas piping is still in the ...
0
votes
2answers
389 views

Why doesn't my gas furnace ignite?

I had a Lennox slp98dfv installed last year - it has a surelight ignition - it now just blows cold air - so I assume the pilot light is out - but not sure how to light it - as u cannot manually ignite ...
2
votes
2answers
327 views

Is Flex Duct Safe To Use In A Crawl Space?

The home I purchased has a crawlspace below an addition that was put on to the original structure. The HVAC contractor that did the work ran 2 long runs of flex-duct to the 2 registers in the room of ...
3
votes
3answers
2k views

How can I cut a cinder block wall to run large round duct through it?

When an addition was put onto the house that I own, the previous owner just ran the duct work into the crawl space through an old basement window. I want to re-route the duct work by actually cutting ...
2
votes
2answers
525 views

Can an 18 inch duct be replaced by 4 smaller ducts?

We have a return air duct that is 18 inches in diameter that had to be soffited. Not a big deal except it is taking up closet space in what is otherwise a very small closet for a kids bedroom. Can ...
1
vote
1answer
2k views

Why is my furnace blowing hot air outside through a PVC pipe?

I turned on my furnace and went outside and noticed hot air blowing out a J-shaped PVC pipe. Is it a vent or error that needs to be plugged?
0
votes
1answer
603 views

Can I cover a high efficiency HVAC vent?

Just moved into a house with a High efficiency HVAC (heating and air conditioning) which vents to the outside ( with a booster fan). the outside pvc pipe is just " open" . no cap, no screen.. i know ...
0
votes
0answers
114 views

AC won't turn on after replacing thermostat batteries

we replaced the batteries on our thermostat after they began flashing for a few minutes. We'd been using the heater up to that point. After replacing the batteries, the heater does not turn on ...
0
votes
1answer
322 views

No electricity going to thermostat

Our old thermostat is working but I want to change to a new one (nest thermostat). I have two exact HVAC unit at home. I change one it works but when I change the second one it doesn't work because ...
2
votes
1answer
76 views

How do I determine how efficient my furnace, A/C, and windows are?

I just bought an older home. The furnace, A/C, and windows are functional, but I suspect there may be some efficiency gains to be made. Is there any way to determine/estimate how efficient those are ...
1
vote
1answer
199 views

Can I connect two separate ducts systems together?

My apartment, which I own, is split upstairs by two hallways. Each hallway has its own A/C unit, to cool 6 single person rooms each. Recently the south side A/C broke. I have called the repairmen out ...
2
votes
2answers
1k views

What does this square icon mean on my Honeywell thermostat?

I have upstairs Honeywell Thermostat showing me a square icon since yesterday. The upstairs AC is not working. It is blowing air since the fan is on but the air is not cold. I opened up the ...
1
vote
1answer
621 views

How to efficiently circulate air to keep room cool?

I live in Indonesia and I have an apartment with a 6.7 x 5m room, which contains a dining table and a couch. In this room are two 1.5PK (13,000 BTU) AC units on the same side of room nearer to the ...
0
votes
1answer
100 views

Why does my HVAC begin vibrating and stop cooling at night?

I am calling a HVAC technician since this is probably too complex a problem for me, but wanted to hear some possible diagnosis. The symptoms are as follows: The A/C is working well during the day ...
0
votes
1answer
370 views

How do I maintain an 80% efficient natural gas furnace?

I have an 80% efficient gas furnace at my house, that is seemingly working well and is configured with an air conditioner. What preventative maintenance should be done to it, and at what interval? Is ...
2
votes
2answers
1k views

Can I remove the fresh air supply that is attached next to my furnace?

It looks like my gas furnace is already vented but I'm not sure. There are two white pipes from the top of the furnace that are vented outside. The furnace is a Trane XR90. We have cold winter climate ...
3
votes
2answers
418 views

What is this name of this vent attachment next to my furnace?

What is the name of this silver vent attachment thing at the bottom of the picture? It is attached to the side of our gas furnace. The black part is an insulated air duct which goes to a vent ...
0
votes
0answers
33 views

How can I determine if a valve complies to MSS?

How to know if the valve complies to Manufacturers Standardization Society (MSS) or not? I want to approve a valve for an HVAC project, but I don't know how.
0
votes
1answer
133 views

Why is my AC blowing from this pipe and freezing up periodically?

I looked under my mobile home and found a hose coming from the flooring. It is blowing cold air out, and it also looks like water has been dripping out. I think that this is normal, but why is all ...
3
votes
2answers
249 views

What material is allowed for a furnace room ceiling material?

What types of material, other than drywall, are acceptable by Ohio HVAC Code for the ceiling of a small furnace room which will: Have return air ducts (only) passing through it to attic space. Butt ...
12
votes
3answers
376 views

Would providing shade for my air conditioner's condensor improve its efficiency?

Our house has two A/C systems; one for the bedroom level, one for the remainder of the house. The compressor/consdensor units are outside the south side of the house, and in direct sun all day, now ...
7
votes
1answer
544 views

Why did an HVAC installer add this PVC pipe?

We recently had a VERY old central heating furnace replaced and I noticed that the HVAC installer added the following PVC pipe shortly before the inspector arrived: The metal vents were already ...
4
votes
2answers
939 views

What is the maximum angle I can set my window AC unit?

We know an AC unit must be angled to allow runoff. But what is the maximum angle and what is the issue with having to large of an angle? I've seen people say the angle is "5/16" or "3/16" but this is ...
0
votes
0answers
33 views

Is my heat pump's condenser fan motor bad? [duplicate]

The other day my AC stopped working. I'm thinking the condenser fan motor has gone bad (unit is ~10 years old). Here is what I did to troubleshoot which led me to believe it was the fan motor. ...
3
votes
2answers
543 views

Can I use an unused wire as a “C” wire?

I just bought a new thermostat that is Wi-Fi enabled and it requires connection to a "C" wire. The old thermostat does not have one running to it, but there are other unused wires. The thermostat ...
2
votes
2answers
114 views

Why is my AC suddenly *heating* my house?

I have a 13 SEER heat pump about one year old. Everything's been working fine, but the AC suddenly started heating my house spontaneously (no changes to thermostat, etc). The outside ambient ...
2
votes
1answer
92 views

Can a problem with heater stack liner cause outside chimney mortar to crack and fall out

I had "high-efficiency" furnace installed in 2009. In 2011 chimney required full grind-out and repoint job, and chimney saver solution was applied to prevent water damage. Service lasted only 18 ...
1
vote
0answers
621 views

Reducing air conditioner compressor vibration noise

I have a two year old Carrier air conditioner with an outdoor condenser. The condenser sits on a plastic pad on the side of my house, and I have two--one for downstairs and one for upstairs. ...
3
votes
1answer
162 views

Should I use a quick or gradual 90 in my flexible A/C ductwork?

To elaborate a bit more. If you are running an 8" duct off the supply, would you do a quick 90 degree towards the destination or do a gradual 90 degree? I would guess a quick would be better because ...
1
vote
2answers
2k views

Which terminal should I connect it to for a “C” wire when none are labeled “C”? [duplicate]

I am looking to replace my old battery operated thermostat with a new wifi model. There is no "C" common wire connected to my old thermostat. There is a blue wire that is at the thermostat but cut ...
0
votes
1answer
2k views

How do I add a C/ Common wire to my “Specific” HVAC system? [duplicate]

I just bought a new WiFi thermostat that requires me to add a C-Wire at the furnace. I have read the questions related to my issue but would like a suggestion on my particular (incredibly OLD) ...
2
votes
1answer
135 views

sealing off sunroom to a/c in summer

what's the best way to seal off our sunroom so we don't pay to cool it? It's really humid AND hot in MS this time of year (avg 90+ F). We have a very "open" house, with a large dining room connected ...
1
vote
1answer
183 views

Replacing Oil Furnace with Heat Pump

My wife and I would like to remove the older oil heat from our home and replace it with a heat pump. We currently have an Amana central air conditioning unit (3 ton), and an oil furnace in the ...
1
vote
1answer
621 views

A/C Condensation from duct getting into drywall

My A/C unit has ducts that run to the second floor, into the attic, to feed some ceiling vents. Today, after several days of brutal humidity, I noticed paint blistering, and in one spot bursting, ...
0
votes
1answer
307 views

Thermostat C-wire replacement using a wall socket?

I have a Filtrete 3M WiFi thermostat. As expected, it takes a C wire, which my apartment doesn't have and the apartment maintenance folks wont' let met wire either. However, there's a wall socket ...
3
votes
1answer
2k views

Where should I tap in to the existing duct work?

Bought a 1981 repo a year ago. The house measures around 900 SQFT. I enclosed the one car garage (10'x20') @ 200 SQFT to serve as an office. The front of the garage is insulated (10') along with the ...
1
vote
1answer
583 views

How to wire a new Honeywell RTF6580WF thermostat to replace a Chronotherm IV?

I have an old Honeywell Chronotherm IV thermostat that I am trying to replace with a Honeywell RTF6580WF wifi thermostat. I have a gas furnace and an air conditioner. Wiring for Chronotherm IV ...
2
votes
2answers
245 views

How can I prevent my clothes dryer door from fogging up?

When I turn the air conditioning on in my house, the inside of the window in the clothes dryer door fogs up. Also, if clothes are left in the dryer, they become slightly damp again. How can I prevent ...
2
votes
1answer
802 views

Should I install a damper above my return air duct for better upstairs cooling?

I have a finished basement, ground floor, and upstairs. The ground floor and basement cool nicely with the AC. The upstairs doesn't cool very well. The returns are really just holes in the drywall- ...
0
votes
1answer
351 views

How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc ...
1
vote
0answers
82 views

How do I troubleshoot my central A/C?

It's 79 outside right now. It's been running for hours and it's remaining 79 inside. I'm in a brand new 2 story home in Monroe, OH. It has rained a lot recently but I just feel like it should be ...