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

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1answer
76 views

Insulating ducts in unfinished basement?

Hi I am looking to insulate circular metal air ducts in my basement because the air reaching some of the farther rooms (from furnace) on the second floor of my home is comparatively much cooler. I ...
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1answer
121 views

What is the rated power of American central air-conditioning control circuit?

I want to know what is the rated power that American central air-conditioning 24V control circuit can supply, which is also the power supply for Nest. Nest gets its power from the 24V control ...
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1answer
43 views

Access 2nd-story burst hydronic pipe through ceiling or floor?

We had a freeze which caused one or more bursts in our hydronic heating system pipes. We know that there is one burst in a radiator, but there may be others, according to the contractors. If there is ...
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1answer
39 views

0v at DC thermostat terminal in furnace

I have an old (mid 80s) Rheem gas furnace I hope will last me through at least one more California winter. It's been known to go down into the upper fifties, so it has its work cut out for it. In any ...
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1answer
61 views

Furnace Fuse Blows Immediately

This afternoon, our Ruud furnace suddenly stopped working. After poking around a bit, I realized that the 3A fuse on the control board had blown. I ran to the hardware store and replaced it, but no ...
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1answer
30 views

Central air winterization and insulation

Do I need to insulate the skinny copper line on the outside to keep it from freezing and bursting during the cold winter months? Anything else I need to do winterize the a.c. unit?
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0answers
221 views

No C wire terminal on my electric plenum but there is on my furnace. How do I solve?

I had a brand new furnace installed recently but also now picked up a wifi thermostat. The problem I now encountered while installing the thermostat is that my system also has an electric plenum as ...
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2answers
139 views

Rain water leaking around attic furnace

I bought a house a few months ago and when I bought it I noticed what appeared to be a water spot on the ceiling of the top floor. Of course I didn't do anything about it until heavy rains over the ...
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2answers
47 views

Air handler unit stops running. Starts when motor touched with metal

How is it going? I just moved into a place I bought. It has separate AC units for both floors. We started having an issue with one of the air handler units. One night when turning the air on the ...
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1answer
351 views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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2answers
1k views

Hvac Fan only blows in 'fan on' mode while heating

Our HVAC Fan only blows in 'fan on' mode while heating. In other words the fan will not blow in heat mode if switched to "fan auto". Both fan on and fan auto modes work when cooling. See image below, ...
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0answers
28 views

Temporary Remove Flex Duct

I am about to replace a load bearing wall in unfinished basement. There is flexible duct attached to plenum that I need to temporarily move out in order to put the beams in. Do i just need to cut ...
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1answer
175 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
104 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
240 views

What is the optimal duty cycle for a furnace?

A heat load calculation of my home says it requires ~36K BTU/hr of heat at a normal winter temperature (40°F), and ~52K BTU/hr at the design temperature (24°F). An HVAC contractor has proposed ...
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1answer
69 views

Home Air Conditioner Problem

I have an air conditioning unit that was here when I bought the house. It was in the 70's here today, but I have an old house and windows don't open so the house was hot. I decided to turn on the ac ...
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1answer
39 views

If water level is rising on its own on oil heating unit instead of going down, could I have a leak? Or something worse?

If water level is rising instead of lowering on oil heater unit, is there a leak? Could something worse happen. Oil man had to drain water to lower water, and said to watch it to make sure it doesn't ...
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1answer
60 views

How do I compare furnace models?

I need a new furnace, and I have quotes from two companies, for three different brands of furnace, Carrier, Trane, and Lennox. Both companies have provided the model numbers of the units they would ...
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1answer
88 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
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0answers
23 views

Is there a “bending rigidity index” of some sort for semi-rigid aluminum ducts?

Some semi-rigid aluminum ducts bend easily and others do not. I want to purchase semi-rigid aluminum ducts online of a specific bending rigidity/stiffness that minimizes sagging but can be easily ...
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0answers
138 views

What makes a furnace pilot valve whistle?

I have a furnace that started whistling, recently. I have read that gas pressure changes can cause this. Others have remarked how seasonal gas changes can lead to a properly-adjusted furnace to ...
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0answers
18 views

Installing a Wifi Honeywell Thermostat with a C wire [duplicate]

can someone please help me out here. I'm installing a Honeywell Wi-Fi Thermostat and this Thermostat requires a "C" Wire. Can someone please tell me by looking at the pictures attached if I have a "C" ...
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1answer
50 views

Does cold galvanizing compound restore the rust protection of a galvanized duct?

The house is a ranch built on slab on grade with a newer furnace in a downflow configuration with A/C. The in-floor clay tile supply lines are in good shape and clean. The original 60 year old ...
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2answers
874 views

Wifi Thermostat to Reznor Garage Heater. No “C” wire connection on terminal strip

I just had a 75000 btu Reznor UDAP garage heater installed. Can I run a "C" wire for a smart thermostat if I don't have a C connection on the terminal strip? There is a C connection on the circuit ...
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1answer
166 views

New thermostat wire: maximum number of wires?

Background: I'm upgrading from a failing ecobee smart thermostat to an ecobee3. The ecobee3 requires all wires for the components it controls to be run all the way to the thermostat (including ...
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0answers
28 views

Pellet Stove Ventilation

I have an Englander PDVC pellet stove that came with my house when I bought it in the spring. Never used it. Currently its vented through the wall and comes straight through the exterior of the ...
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1answer
119 views

Which direction is the airflow through my furnace?

There's multiple lines of ductwork along the side, and up top. So what's the correct direction of airflow (red or green in the image below)?
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0answers
27 views

How to connect 4 fan coils with one wall control thermostat?

I have 4 fan coils (Sabiana sk-22)and I want to connect them with one wall control thermostat. How can I do?
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2answers
771 views

How do I cut a straight line in an installed wood floor for a flush mount HVAC vent?

At some point a previous owner installed hardwood flooring in my house. Nice. They did not however make a hole for the front entryway heating vent. The duct and duct outlet exists in the crawlspace ...
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1answer
43 views

Can I vent room air to the outside?

The building interior gets hot during the day and stays hot during the evening when it is much cooler outside. It would be a really great option to simply vent the hot air outside instead of having to ...
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1answer
445 views

Air conditioning unit sitting on the ground

We've lived in our house 11 years. Our air conditioning (condenser) unit, the big boxy thing sitting outside, is not sitting on a concrete slab. It's just sitting on the ground and we noticed this ...
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2answers
121 views

Can a 110v 3-wire thermostat be hooked up to a 110v 2-wire condo setup?

My condo that was built in 1968 has an old thermostat(rheostat type) which supplies 2 thick gauge black wires of which one is live and the other isn't. This regulator is hooked up to a blower ...
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1answer
49 views

How to remove old A/C piping in my house?

When I had my new A/C installed I moved it to the other side of my house (right next to the furnace), so now I have a bunch of old copper piping running about 30 feet from one corner of my house to ...
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3answers
173 views

Is an HVAC license required for DIY home owner AC installation in the State of Georgia?

Does anybody know for certain if in the State of Georgia, an HVAC ("conditioned air") license is required in order for a homeowner to install their own HVAC system?
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2answers
114 views

Is the Thermostat Wiring Correct

When I moved in to the house the first thing I changed was the old mercury style T-stat to a digital one, I went wire for wire, and it has works (knocks on wood) so far. Now that I have been reading ...
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3answers
91 views

My Goodman a/c motor fails due to high voltage

I have got a brand new goodman unit. The motor kept stopping after few hours an the tech replaced the motor. It still had same issues.. I was told that the voltage coming into the unit is too high.. ...
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1answer
61 views

what is the cause whereby compressor working gets hot and stops, after cooled down picks up

My challenge was that, I have this refrigerator I'm working on and after awhile it is working and then the condenser become hot as the compressor discharges excess heat, which as time goes on ...
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1answer
97 views

Downsides to staple up radiant heat, besides cost?

I'm considering doing a radiant heat retrofit into my home and removing an older forced air system. The plumber is proposing a staple up from the basement into aluminum plates with PEX tubing with a ...
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1answer
41 views

How to control system with 2 condersors+evaporators and 1 blower

I have problem with the control the HAVC system using 2 condensors + 2 evaporatora with one blower. I used 2 thermostats (4 wires/thermostat) to control. But the problem is when i turn on (cool ...
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1answer
94 views

Can the back side of a window type aircon exhaust in an empty ceiling area?

I'm planning use a window type A/C on my little attic room. My A/C unit is just .5 HP, just enough for the small room. The problem is there's no proper exhaust area like the standard Window type. ...
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1answer
517 views

AC Blower running very slowly

I have a Ducane heat pump. When running in AC Mode, the outdoor fan and compressor kick off just fine. The blower fan seems to kick off as well, though it's not putting out very much air. I can ...
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4answers
93 views

Why is humidity high from one unit but not the other?

Two months ago, I posted about our upstairs a/c not cooling all of a sudden. I ended up replacing the capacitor for the blower fan and the contactor, which did the trick. AC cools!!! However since ...
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2answers
79 views

The house is not cooling

What would cause the outside ac motor to run than stop than start up again and continue this random stop and start cycle constantly. The house stopped cooling
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1answer
116 views

central A/C Turns back on 30 seconds after shutting off

First of all, the a/c system is probably 30 yrs old. The outside unit stays running when the inside unit shuts off. After about 30 seconds, the inside unit turns back on again, and will sometimes only ...
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1answer
46 views

How can I plug a hole cut in a window pane for a portable A/C unit?

I just moved into a room where there is a portable A/C unit. To create a vent for the unit, a hole was cut in the glass of one of the window panes that spans about 13.5 cm. I was told that the unit ...
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0answers
62 views

Smaller Footprint of new Furnace Base Cabinet

Replaced downdraft furnace in 1950's ranch house built on slab. Base cabinet of new furnace has a smaller footprint than the original resulting in a 4in. gap between the edge of the cabinet and the ...
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2answers
513 views

Temporary fix for bad contactor?

After doing some replacement for the ac, the contactor stopped working. It won't close when I turn the ac on. when I pushed it in, the compressor was able to start. I can't go out to find a new one ...
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1answer
43 views

HVAC tripping breaker - things to check before replacing?

HVAC system (we're in Houston, it's still hot here) stopped working Tuesday. A/C guy came out, determined it was tripping breaker. Would trip immediately after resetting, but after a couple of ...
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38 views

Can my A/C unit knock out my whole trailer or is it coming from the main box outside causing the problem?

I'm confused. Do you know if my air conditioner unit would blow out the main power in my whole trailer if the box inside my house isn't tripping? It keeps making a very loud popping noise under my ...
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4answers
955 views

Can a homeowner without a Section 608 EPA license legally connect his own gauges to his own air conditioner if the unit uses 410a refrigerant?

It has been suggested by at least one moderator on this site that EPA Section 608, which restricts who can purchase and handle refrigerant, including who can connect a set of manifold gauges to a ...