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

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4
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3answers
832 views

Advice for replacement/repair of an HVAC with a cracked heat exchanger?

My townhouse has a downflow 1994 Rheem 2.5 ton HVAC unit on its roof (combines both A/C and heat). We have had two issues with the unit and have been in the townhouse for a little under two years. In ...
4
votes
2answers
3k views

Can I run heating duct work through the attic?

Problem... (in Buffalo NY) We just about finished remodeling our master bedroom. Everything insulated, drywalled and we're living in it. Now that the winter is upon us, we're already finding this ...
4
votes
5answers
10k views

How often should I run a bleach and water solution through condensate lines?

How often do you need to run a bleach and water solution through the condensate drain lines (of a heat pump) to keep the bacteria away? What are the recommended parts (e.g. 1 part bleach, 10 part ...
4
votes
2answers
2k views

What are these two pipes coming out of the house?

I am trying to figure out the purpose of a couple of pipes that are currently coming out of the house. First, a couple of notes: One-story house. HVAC system is in the attic. It is winter here. ...
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 ...
4
votes
2answers
675 views

Do joints in adjustable duct elbows need to be taped?

Do the joints in adjustable duct elbows need to be taped as well once they're adjusted or are they considered air-tight?
4
votes
2answers
1k views

Are there high flow floor heat registers available?

The weather has been pretty warm lately so we've been running our A/C. I noticed that it didn't seem like much air was coming out of the registers, so I checked to make sure the blades/louvers were ...
4
votes
3answers
1k views

Is an interior laundry room without an HVAC vent a code violation?

Currently looking at a home which has a nice 2nd floor laundry. Vented dryer, nice rack for hanging clothes, etc. However, it's in the center of the home and does not contain an HVAC (central air) ...
4
votes
2answers
72 views

Resources for designing new HVAC [closed]

Our house is a bungalow with full basement and is currently heated via electrical baseboard heaters in every room. I'm converting this to a central air system heated by a gas furnace, and possibly ...
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 ...
4
votes
5answers
14k views

Should I insulate air conditioner coolant pipes?

I recently replaced some rotted insulation on the coolant pipe that runs out of my AC unit and into the evaporator in my house. When cleaning inside the actual AC unit itself I noticed that the ...
4
votes
1answer
2k views

What would cause my furnace to only work with the filter removed?

My Carrier furnace works fine without the air filter in place on the return. With the filter in place it works for a while and then stops with a complaint about "limit, or flame rollout is open" ...
4
votes
2answers
108 views

DIYer to skilled tradesperson

What is the process a DIYer has to go through to become a skilled tradesperson? Are the only options apprenticeships, or are there other paths to follow to learn a trade/become licensed? What type ...
4
votes
3answers
84 views

How to find areas where heat/coolness are lost?

I live in a 2-story rental townhome (basically an apartment with 2 stories). Our central air/heat system isn't really the best at keeping the upstairs and downstairs the same temperature whether in ...
4
votes
2answers
737 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 ...
4
votes
3answers
3k views

What's causing the rumbling sound when my furnace kicks on?

I have a new, 3-year old, high-efficiency furnace in my home. Last year it started making a slight whining noise that was audible during the very first stage, before the blower motor started. No ...
4
votes
1answer
1k views

Can I reroute this air duct?

I'm quite new to dealing with HVAC duct-work. We would like to install a suspended ceiling in this room. Since the finished ceiling will be higher than this duct-work, we're going to build drywall ...
4
votes
2answers
9k views

Workarounds for single-zone HVAC? Second thermostat? Adjust vents?

I have a two story brick home built in 1970 with a relatively new HVAC system blowing through original ductwork. In the summer its too hot upstairs and too cold downstairs. I know that the full ...
4
votes
1answer
681 views

ductless AC split systems?

Does anyone have the ductless split AC systems offered by Mitsubishi, etc.? Is installing them a DIY job? Can you share your comments about them, in general? Edit: Inspired by DA01 comment, I'd ...
4
votes
1answer
989 views

What's wrong with my thermostat (fan / limit control)?

I previously asked about wiring the White-Rodgers fan/limit control on my wood stove. It's now wired and the wood stove is fired up. I ran the fan wires to the fan (hot) and I capped the limit ...
4
votes
1answer
192 views

How can I determine if my HVAC system has features which are not currently wired to my thermostat?

I recently upgraded to a Nest Thermostat. This new thermostat supports many more terminals and features than my previous thermostat. My old thermostat had the basic terminals; G,R,C,Y, and W. I am ...
4
votes
2answers
704 views

How do I improve heating in back room of house?

The back room of my house is quite warm in the summer. The room is on the north side of the house (Alabama, USA), so the outside walls don't get direct sun exposure. The attic insulation is a little ...
4
votes
2answers
591 views

Connection for C wire on Mastertrol Mark V zone control panel

I have spent hours searching the web for information on this 20+ year old zone control panel, which supports 3 zones of Heat and A/C. The thermostat I'm replacing (on Zone 3) connects to T4/T5/T6 as ...
4
votes
2answers
701 views

What are effective ways to frame a return air duct?

Consider an in-floor return air duct that is 32" x 22". A standard air filter that closest fits the register is 30" x 20". What materials should I use to frame the duct so it will snugly hold the ...
4
votes
1answer
714 views

two condensate drains?

we just had a new AC system installed in my florida house. the unit is in the garage, and the air handler is vertical with the evaporator on top. the unit he removed had 2 condensate lines: one that ...
4
votes
3answers
2k views

How effective is a heat pump for AC and a heat pump/furnace for heating in New England?

We currently have a central AC unit and oil furnace. The AC is broken and the furnace is old, so we are thinking of replacing both sometime in the next year. We are considering replacing the AC with ...
4
votes
1answer
534 views

Why won't the fan run independently of the air conditioner?

I have central air and heat, with a Nest thermostat. My system has Y, G, R, C and W wires coming out of it: which are wired into my Nest like so: In between, there is a splice where the C wire is ...
4
votes
3answers
667 views

How can I redirect the discharge of my forced air vent?

An AC/heating register on our kitchen ceiling blows air directly toward a gas cooktop causing the flames to flicker. Adjusting the register doesn't seem to make a difference. I've looked into air ...
4
votes
1answer
1k views

Adding AC to forced air system

We have an old house that happens to have forced air. Unfortunately, according to an HVAC tech it looks like there aren't sufficient return vents to add a compressor to our furnace. I guess I'm ...
4
votes
4answers
327 views

Can I reduce static pressure in one room by adding a vent to an adjoining room?

Our return vent for our hvac is right outside the master bedroom. The master bedroom gets very little airflow with the door shut. It was recommended that we add secondary return duct in the master ...
4
votes
1answer
428 views

How well do whole house humidifiers work?

We are moving to an area where it gets cold and snows in the winter. We come from a desert area where it is never very cold except for the dead of winter, and where we use the heater very seldom. We ...
4
votes
1answer
8k 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 ...
4
votes
1answer
2k views

How should one size ductwork for a new air return duct?

I recently had a contractor build a wall which split one room into two. The new room is an office with two computers, and four monitors. It gets very, very hot, until the air conditioning turns on, ...
4
votes
1answer
430 views

What could cause a furnace to short cycle?

My Ducane MPGA100B4B furnace is shortcycling (2 minutes from fan on to fan off) The thermostat's Heat Anticipator setting doesn't seem to matter for the on-time, maybe the offtime changes The ...
4
votes
2answers
750 views

Where should I install a Pellet Stove to supplement my boiler?

We are purchasing a pellet stove insert for our single floor 1200 sq. ft. home. We are doing this to reduce our dependency on oil (hot water boiler), which we use to heat the house with baseboard hot ...
4
votes
3answers
2k views

Why does the pilot light go out when the furnace is running?

Every time the furnace fires up, it blows out the pilot light. Sometimes it will run a full cycle and blow out when it shuts down, and sometimes it will blow out about a minute into the cycle. We ...
4
votes
0answers
124 views

When cleaning HVAC ducts, is treatment for fungi and bacteria routine and mandatory after 20 years? [closed]

Is treatment for fungi and bacteria routine and mandatory after 20 years? Or should we test for fungi or bacteria first? This would be in addition to air duct cleaning.
3
votes
4answers
396 views

Air conditioning on a shoestring budget

Without purchasing expensive air-con units, or solar panels - and the associated moutings and electrical paraphernalia, is it possible to create a temperature difference of 10-20 °C using materials ...
3
votes
3answers
13k views

How much less power does a three-phase A\C unit use as apposed to a 220v unit?

I'm planning to install a 5 ton central AC. I'm deciding between a condensing unit that runs on 220V and a costlier unit that runs on 207Y three-phase. My understanding is that three-phase motors use ...
3
votes
2answers
442 views

Is there a trick to getting round HVAC duct pieces to fit together

I have been doing some basic HVAC duct work as part of a remodeling project and I can never get the pieces to fit together without massive amounts of elbow grease and mangling the ends. Is there some ...
3
votes
3answers
2k views

Can I sense filter replacement need based on filter pressure drop?

I should first point out that the system I'm referring to will be a self build DIY project. Fan and Filters being the only items purchased complete, And I'm still in the design phase but I'm not a ...
3
votes
3answers
115 views

Geothermal Resources

I am very interested in learning more about Geothermal solutions for my house. What are the best resources for learning about and planning a Geothermal systems for a residential house? Also, does ...
3
votes
2answers
2k views

Why does my window air conditioner cool but not dehumidify?

I have a brand-new 5000 BTU Frigidaire window air conditioner, and it seems to work fine except that it doesn't reduce the humidity in the room. I turned it on last night, and the temperature was 81 ...
3
votes
2answers
790 views

Why is my furnace filter alarmingly clean?

I have central air and heat at my appartment I moved into about 6 months ago. Today I decided it was probably long past time to figure out how to change filters in the furnace so I poke around until I ...
3
votes
1answer
3k views

Convert line voltage heating system to use low voltage thermostats

I currently have two line voltage ceiling radiant heating systems in my condo each with their own DPST thermostat. I'd like to use low voltage thermostats such as the nest. I found this ...
3
votes
2answers
2k views

Can I increase air volume by adding more fans?

I have a straight 25 foot rectangular duct that is 0.9 sqft in cross-sectional area (11" by 12"). There are openings on either end, and nowhere in the middle. I wish to move about 1000 CFM through the ...
3
votes
2answers
2k 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 ...
3
votes
2answers
3k views

Is a lip necessary on an HVAC ceiling register boot for use with flexible ducting?

I've installed some new ceiling register boots to use with flexible ducting and realized after install that they have a smooth connection with no lip. I'm assuming they are made for metal ducting, as ...
3
votes
2answers
1k views

What kind of wall switch is needed for a natural gas fireplace to ignite consistently?

When we moved in, our natural gas fireplace worked well: Flick the switch & it would ignite. Years later, it started acting erratically: Sometimes, the switch worked, other times, no luck. We'd ...
3
votes
2answers
1k views

Is voltage too high in C wire going to thermostat?

I've managed to add a C wire to my thermostat. I then decided to check the voltage between the R and C wires, and find that it read as 27.8 volts, not the 24 volts it was supposed to be. Could this ...