Questions tagged [hvac]

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

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1answer
39 views

Dual hose portable AC unit creating negative air pressure

I bought a dual hose unit because it's supposed to not create negative air pressure in the room, but I can definitely feel the air resistance when I go to close the door to the room it is in. When the ...
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2answers
56 views

intermittent compressor on elderly dual-fuel heat pump

I have a 23 year-old dual-fuel 2.5-ton heat pump; it is a split system, air handler and furnace in the crawlspace, compressor outside. I use it very little in the winter, mostly heating with wood; I ...
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1answer
31 views

Furnace Displays Heat Pump mode when AC is running

I have a new Trane S9X2 furnace I purchased this winter. I want to make sure that everything is setup correctly now in the cooling season. I noticed that the furnace displays "HP1" when the AC is ...
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13 views

Connect two LP-GAS High-Eff +95% Furnaces to one LP Tank

Connect two LP-GAS High-Eff +95% Furnaces to one LP Tank will reduce supplier refill to one location on House. Furnaces 100K BTU and 60K BTU. To reduce refill to one location (currently two tanks on ...
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2answers
72 views

What's the difference between commercial and residential tankless water heaters?

I'm trying to figure out the difference between two tankless water heaters, produced by the same manufacturer, one a "Commercial" and another a "Residential". The commercial one is allowed to be used ...
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1answer
45 views

Central AC Is not Cold

My AC will turn on but will not blow out cold. I'm rebuilding the whole system, ductwork and all. I've shorted the thermostat's red (power), yellow (a/c compressor), and green (fan) wires together. ...
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0answers
56 views

Was the condensate pump in my air conditioner unit wired incorrectly?

My condensate pump stopped working - I noticed because there was a lot of water coming out of the condensed drain. I bought one brand new but when I disconnected the old one, I realized that the ...
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0answers
33 views

Rewiring for Nest Thermostat - Current ABCD Configuration Carrier

So I would like to use a Nest thermostat on my carrier system. I have the ABCD wiring configuration from current thermostat to the board on the furnace. On the attached image, you'll see three brown ...
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2answers
53 views

Minimum length of mini-split AC line

I was considering buying a cheap mini-split AC unit to cool a small room (10ftx10ft) over the summer now that we spend more time working from home. There are several units on the market. However I'd ...
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1answer
37 views

Heat-pump style AC is not putting out cool air

I live in the Northern area of the US, and I have a heat-pump style AC unit. So there is an AC unit with big fan outside my house, and there is a furnace in my attic. I bought this house 10 years ago ...
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3answers
45 views

Can insects get into a house through the ducting?

I have a study that normally has the door closed and all the windows are very tight, modern windows, yet I keep finding insects, especially flying insects like lady bugs and wasps in the room. Can ...
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1answer
58 views

Why does this wall in my basement have so many vents?

I have a wall at the foot of my stairs that has 3 vents in about 5 ft of wall. One of them ducts straight to the HVAC system, the other two just open into the unfinished storage/utility (furnace, ...
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0answers
47 views

Cooling a Room with No Windows

I am trying to determine the most effective way to cool my bedroom which runs about 5 degrees warmer than the rest of the living space: Questions: What is the most effective way to bring the bedroom ...
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39 views

Any way to reverse engineer split ac inverter compressor speed?

Summer has come and I've got myself an oversized inverter Air Conditioner (1.5 ton for 120sqft room) as suggested by some YouTubers. Details: Outdoor temp day: 43C, Night: 30/35 Relative Humidity: ...
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0answers
31 views

Why would a wall-mounted AC unit with a digital thermostat seem to be reading outside temperature when the fan isn't running?

My apartment has a wall-mounted AC unit with a digital temperature setting, which works great, but it has a consistent problem where its thermostat appears to read much differently than the actual ...
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60 views

Need help connecting “C” wire, unknown red and white wire from one unit to the other

We are replacing our old thermostats (installed in 2006) with two smart thermostats. We have 2 separate units and thermostats. We have an unused blue wire (c wire) at both thermostats. We thought we ...
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1answer
27 views

Both reusable and disposable furnace filter?

I recently discovered that my furnaces (Rheems) have reusable "permanent" filters, but they also have a disposable filter tray. Are they intended to both be used simultaneously, or are homeowners ...
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1answer
27 views

Exterior air conditioning pipe insulation

I live in the Southern California desert and am doing some renovations to my house. Our AC line runs on the roof from the center of the house 25' to the west side and down the wall to where the ...
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0answers
15 views

Is PVC ventilation duct safe for health in long term? [duplicate]

Some contractor says PP is safer (the arguments is it is used in food packaging...) and PVC will degrade and release toxic materials after 10+ years. But in http://en.wikipedia.org/wiki/...
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24 views

HVAC Wiring Help

A little backstory should help... my parents built the house in 1996 with no central air. They added central air in 1999 and it was fine till three years ago. We had a programmable thermostat ...
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1answer
50 views

Change to different condenser fan motor model?

I have an HVAC system that has a condenser fan motor that has gone bad. The motor is no longer available. What considerations do I need to make in order to replace the motor with a different motor? ...
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0answers
16 views

How to seal seams in a traditional Cedar wood dry sauna

I just built a new, indoor, traditional dry sauna made with Cedar wood. https://www.costco.com/almost-heaven-bluestone-3-person-steam-sauna.product.100485086.html During assembly, some of the ...
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0answers
27 views

Rheem RGDG unit turns on w/thermostat off, blower come on and inducer motor switches off and on

I've having a problem with my rheem model rgdg-10nbrjr The air conditioning works, turning it on at night it blows cold air and the house indeed gets cold. However the furnace unit itself ...
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2answers
16 views

Looped air conditioner condensate line not draining?

Using our split air conditioner for the first time, the wall unit started dripping water. Its condensate tube runs through the wall into an adjacent attic and then into the DWV vent stack. The tubing ...
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4answers
423 views

Does leaving the Central AC on all day and all night cause the motor to burn or compressor line to freeze up?

I'm not suggesting doing this or whatever, I just want to know the answer. Let's say it is 80 deg F outside and I put the AC on 50 deg F. Obviously this will cause the AC to run all day, would this ...
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1answer
881 views

Replaced Blower Motor, but A/C won't stay on unless power button is held down

My HVAC has an electric furnace blower motor for both heating and cooling. I called a repair guy out who explained that the capacitor was good, I just needed a new motor because it had gone out. I ...
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1answer
30 views

Heat Pump doesn't work in AC mode, but heat mode is fine

I have a heat pump for my house's heating and cooling. We had our first hot day of the year last week, so I switched it to cool mode (heretofore it had always been in heat mode). When in cool mode, ...
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0answers
4 views

Older Tempstar furnace, fan runs all the time though set on auto, suspect high limit switch, cannot find part

Older Tempstar furnace, fan runs all the time though set on auto, blowing cold air when flame is off, tried smacking high limit switch, that worked, but problem remained when furnace temp turned back ...
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1answer
42 views

Should I install my split AC outdoor unit further away so it's in the shade?

So i just got a 1.5TR split AC (LG LS-H18VNXD) and i have two options. Install the otudoor unit (ODU) just behind the indoor unit (IDU) on the outer wall, so piping distance would be minimum possible,...
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0answers
29 views

How do I design an ice house?

Where can I find how to design a cold room storage building? I have a 12x12 shed that I use as cold storage for tree seedlings for about a month each spring. The present construction is 2x4 walls ...
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1answer
19 views

Thermostat fan control on old furnace without circuit board

I have an old gas furnace without a circuit board. Just a 4064 fan limit control, 24v transformer, gas burner control and fan. I wired a new wifi thermostat in. It works great. I would like to be able ...
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1answer
18 views

Replacing swamp cooler pads

I have a AercoCool Pro 4800 swamp cooler roof unit and need to get new rigid pads for it. Do the pads need be specific to the brand according to the cooler's spec sheet, or can I use any pad that is ...
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1answer
403 views

Dryer vent: proximity to electrical wires

We recently moved into a new home, and the ductwork for the (as yet uninstalled) LG DLE3500W electric dryer is the flexible foil type. To avoid an additional bend in the duct, it runs across some ...
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0answers
23 views

Upstairs is getting frigid at night during cool nights

I have a dual zone Lennox system, and it cools well, but for the past few weeks it seems to run away at random cooling the upstairs to several degrees lower than requested. We have EcoBee thermostats ...
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0answers
42 views

CFM ratings of inline duct fans far exceed the ratings for their intended duct sizes. What are we to make of this when designing a system?

My garage is 25×29' with 10' ceilings, so 7250 cf. I'm hoping to be able to turn over the air every 3 minutes or so, so aiming at using 2 fans rated at a total of 2400cfm. The fans I'd like to use ...
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0answers
11 views

Replacing flexible.duct work on AC unit

I purchased the correct size flexible duct for the air supply, but was unaware that the return side is 2 inches bigger. Since I am unable to purchase the bigger size until next week, is it safe to run ...
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1answer
37 views

Best tool for cutting a 2" horizonal sloped canal cut through a 11' plaster/lath internal wall

In one room I need to cut groove into a wall to accommodate a condensate drain from a minisplit air handler/evaporator in an adjacent room. I know I could use a pump but I rather rely on old fashion ...
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2answers
52 views

Natural AC, Stream Powered heat exchange

I will keep this short and clear as I can. My home has a creek that runs through it about 20' from the side of the house. It is shaded and quite cool even in the summer heat. If I got say an ...
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2answers
57 views

Minisplit ductless communication wire question

Simple question and I am obviously missing something, but the manual calls for 14/4 to be used as the communication/power cable. That is 1 wire for communication, 2 hot wires and lastly one for ...
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0answers
16 views

ductless air handler install

So I am about to embark on an install of a 6 zone ductless system and I have 2 questions around installing the air handlers in each bedroom. I am using a branch distribution box which needs to be ...
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0answers
17 views

DIY Solarium / Four Seasons Room - Project Planning Advice

I am located in Columbus, Ohio. I currently rent, but I am planning on buying a house in the next two years, and I want to get started on planning for this project. My wife is a houseplant enthusiast, ...
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1answer
91 views

Groundwater cooled heat exchanger - forced air

I have kind of a crazy idea I have been scheming - I live in Alaska, and have a private well - the groundwater here is very cold(40-45F) or so. The last couple of summers have been miserable hot up ...
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1answer
50 views

Connecting a C-wire to a Burnham Independence Boiler

I would like to install a Sensi thermostat which requires a c-wire. I am planning to run a new thermostat wire, since the old one was 18/2. I am trying to figure out the correct way to wire the c-wire ...
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1answer
36 views

Can I keep my existing ductwork when replacing a furnace with a heat pump and air handler?

I currently have an over-sized furnace for my home square footage. I'm happy with the duct's performance, they are quiet. The furnace is 27 yo and I'd like to replace it with a heat pump and air ...
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0answers
10 views

Weak airflow after replacing furnace and add new A/C

I had Furnace HVAC before and I made a mistake not knowing what I had. We never had A/C. Recently I purchased this package from Costco: LENNOX ELITE SERIES AIR CONDITIONER SYSTEM XC13 LENNOX 80% 2-...
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0answers
18 views

How to connect different HVAC components each with a blower

If there are multiple HVAC components, each has its own blower; for example: Furnace/heater with blower : for heating Air handler with blower : for cooling and dehumidifying, and (optional and if the ...
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1answer
127 views

Should I proactively replace my Federal Pacific service disconnect boxes? (not a breaker panel)

House was built in 1985. On one of the exterior walls, there are two Federal Pacific service disconnects for my outside HVAC units. The label on the first one indicates it's an FPE model R160, which ...
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1answer
21 views

York Diamond 80 HVAC - Fan Only Works With Heat

Model P4HUB16N08001A. NEST thermostat says problem with wiring - relay clicks but fan does not start - outside unit runs. Installed "dumb" thermostat and fuse blows - does not try to start. Fan ...
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0answers
47 views

Ecobee 4 - C Wire Connected but no power

I have an extremely old HVAC system (Goodman Janitrol Model GMNT060-3) and had a previous WiFi thermostat connected with a C Wire. I am now upgrading to a ecobee4 and cannot get any power to the ...
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1answer
44 views

Old Rheem rhqa 1000 to thermostat wiring help

I cannot figure out how to wire my 30+ year old AC to my lux dmh110a thermostat, I do not have the old thermostat to reference. It seems to be 4 wires coming out of the air handler and to the ...

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