Questions tagged [furnace]

The furnace is part of an HVAC or central heating system used to generate heat. Typically this is done with gas, a heat pump, or an electric element. For hot water and radiator based heating, use the boiler tag.

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18
votes
10answers
29k views

Do thermostat-controlled, auto-adjust HVAC vents exist?

The residential forced-air HVAC systems I have seen are controlled by a single thermostat in one room. One has to manually adjust the vents in order to adjust the temperature in other rooms. Is ...
11
votes
7answers
57k views

Does lowering the blower speed of a forced-air furnace lower its efficiency?

My gas furnace has two options for the blower speed: MED, and MED-HI. It had been set on the higher speed, but that was too harsh, so I lowered it to the slower speed. Does that have any impact on the ...
10
votes
2answers
78k views

What does a Summer/Winter switch on furnace air ducts do?

On some of our furnace ducts, there is a switch/valve for Summer/Winter or S/W. What does changing this switch/lever accomplish? Can bad things happen if I forget to switch it? Bonus question: ...
10
votes
8answers
5k views

How can I audit my furnace?

I want to keep track of when my furnace is on, with an eye to reducing how much energy I use to heat my house. I could compare it with weather data (temperature, wind speed, precipitation). I could ...
10
votes
2answers
93k 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 ...
9
votes
2answers
2k views

Should I insulate steam pipes in the basement?

I have a steam-radiator heating system. The furnace is in the (unfinished) basement, and the steam-carrying steel pipes spread out across the basement ceiling before going up into the rest of the ...
9
votes
1answer
612 views

What does this device on my new furnace do?

Can someone please tell me what this is? I had a 35-year old oil furnace replaced recently and the new furnace is obviously more complex and has many safety features the old one didn't. I've looked it ...
9
votes
1answer
574 views

Should I relocate the HVAC unit in my attic?

I have had a couple of estimates to replace our HVAC system and one contractor says he would relocate the system to a more central location in the attic. One says there is no need to relocate. There ...
8
votes
7answers
112k views

How much energy will continuously running a furnace fan use?

We have a bi-level (tri-level? There's a small entry way and utility room, then an upstairs living area and master bedroom and a downstairs living area with bedrooms) in mid-Michigan. The downstairs ...
8
votes
3answers
2k views

Why are furnace/central AC blowers so inefficient?

I can buy a ceiling fan from Home Depot capable of moving 5,000 CFM of air for about $50, and it uses a mere 50-60 watts while doing it. By contrast, most furnaces seem to have blowers that operate in ...
8
votes
9answers
20k views

Where should my furnace filter go in a Lennox G40UHX series furnace?

I have a Lennox G40UH(X) series furnace, which is installed in our attic (We have a single-story house on a slab). Because the furnace is installed in the attic, it is "laying down" on its side, and ...
7
votes
6answers
126k views

Why does my furnace need frequent power resets?

I have a NOMA Programmable thermostat attached to my furnace. The set point is usually around 21 degrees, and the room temperature is reading around 17 degrees. The furnace is not coming on. However,...
7
votes
4answers
1k views

Rust and ash in my AC/furnace - should I be concerned?

TL;DR - Furnace/AC generates a lot of rust flakes and ash, not sure what this means. UPDATE - An inspector came by to look at the furnace. While the inspector didn't find anything broken, he said it ...
7
votes
1answer
983 views

Decrease dust in an old house, forced air

My house was built in 1940. I have noticed the forced air pushes out a lot of dust. This is evident from lint collecting on the bathroom vanity below a vent. It only collects lint during Summer and ...
6
votes
2answers
3k views

Can an electric dryer be next to the gas furnace?

I intend to relocate my washing machine and electric dryer within the basement. The dryer will then be about 2 feet from the furnace. Is that OK?
6
votes
2answers
403 views

Is there a way to find out how often your furnace is running?

With winter finally setting in, and being the first year in our new house I would like to put some sort of measurement on how often the furnace is working, before I get the bill. Are there any known ...
6
votes
6answers
14k views

How often should the air filter in the furnace be changed?

Does the period of change of this air filter have an affect on the longevity of the heating and a/c system? What is a good rule of thumb to require replacement?
6
votes
3answers
18k views

Do I need a rain\snow cover on this furnace vent?

Just bought a house that had a new furnace installed this summer. Vent number 1 in the image is for the furnace (2 is the water heater and 3 is sump). As you can see in the image, 2 and 3 both would ...
6
votes
3answers
73k views

Which way does air flow into a furnace?

Which way does air typically flow in a furnace? Put another way, does the filter usually sit before the incoming cool air reaches the burners or after? I'm trying to figure out which way the air flow ...
6
votes
3answers
5k views

How can I prevent my furnace and A/C from slamming doors?

What specifics will I need to collect to figure out if our furnace and A/C are sucking too much at the source/intake? I don't know the proper terminology for these things, do forgive me for any ...
6
votes
7answers
15k views

How do I prevent ice stalagmites from building up on the furnace exhaust?

I have a high efficiency furnace that exhausts via a pvc pipe out the side of the house, the trouble is the moisture from the exhaust forms an ice stalagmite in my driveway in the cold weather. Are ...
6
votes
1answer
3k views

Insulating ducts in a crawlspace

Consider a source duct from the furnace/AC. The ducts run in a vented crawlspace. The floors atop the crawlspace are a mix of hardwood and kitchen vinyl. The symptoms are: the longer run vents aren'...
6
votes
1answer
27k views

How many wires can be connected to the C terminal at the furnace?

I'd like install a new Wi-Fi thermostat. The old one didn't have a C-wire but luckily there is an unused wire on both sides (one coming out of the wall and one at the furnace not connected yet), so I ...
5
votes
3answers
2k views

Should the fill line be removed when decommissioning an old oil tank?

So, I have a contractor decommissioning my old 650-gallon oil tank. There is a 3" metal tube coming out of the ground from the tank that is what I believe to be the receptacle used to fill the tank ...
5
votes
4answers
3k views

Why do I have two parallel gas pipes?

I've got a water heater and a hot water radiator furnace sitting next to each other, both on gas. The strange thing is that there are two parallel gas lines feeding each one of these which come from ...
5
votes
3answers
2k views

Can I close the garage vent on my furnace?

My furnace duct system has a vent in the garage, right over the furnace. Is it necessary for the proper operation of the furnace to keep that open? I'd hate to waste the money heating up my garage, ...
5
votes
1answer
1k views

Why does my furnace only work after power reset?

I’m having issues with my furnace sometimes not kicking on. I hear the furnace start, But then it will not fire. However, If I go down to the basement and flip the power switch off and on the ...
5
votes
7answers
8k views

How to Lower the Ouptut of Oversized Furnace

Questions I would like to lower the output capacity of my furnace if possible. How can I do this? Is it worth doing, or should I just live with it? Is there an easy way? Some ideas: replace burner ...
5
votes
3answers
27k views

Why do our baseboard heating pipes make a loud banging noise after a new furnace was installed?

We had a new furnace installed about a month ago. The heating in our house is hot water baseboards. Ever since the new furnace was installed, when the heat comes on or turns off, there is a loud ...
5
votes
3answers
70k views

If I turn off the breaker to the Gas furnace will the pilot light go out?

I need to turn off the breaker for the furnace but am afraid this will turn off the pilot light to my gas furnace & I don't know how to relight it. Are any special steps necessary to prevent ...
5
votes
4answers
13k views

How can I avoid cold rooms due to combustion air intake?

I have a newer split level house (2006) with unfinished basement. The natural gas furnace is on the lower level in a utility room that is also laundry and bathroom. There's an enormous 8 or 10" pipe ...
5
votes
1answer
217 views

Are discount furnaces safe to use?

More newbie questions ;-) The house we're looking to buy has an older furnace that "may be manufactured by the Permier/Consolidated furnace company" according to general inspections. We're in the ...
5
votes
5answers
4k views

Why does a furnace need a fuse?

Rural USA. We just had a gas furnace installed. The new furnace has a 1-gang junction box with a switch and a fuse. It's the 21st century, here, I swear. And not England. The furnace circuit is ...
5
votes
3answers
10k views

How do I prevent harmonic resonance hum in PVC vent of newly installed hot water heater?

I just had a new power vented water heater installed (HTProducts Phoenix Light Duty) in our crawlspace. The contractor that put it in used part of the existing 3" concentric vent from the furnace we ...
5
votes
2answers
8k views

What could be causing vibration in my furnace?

I have a vibraton in furnace only when flame is lit. Blower motor seems fine. Is this vibration normal? Recently replaced inducer motor. Heat exchanger has been replaced once. Does not appear to be ...
4
votes
5answers
154k views

Why does my pilot light keep going out?

My furnace pilot light keeps going out so I changed the thermocouple. Now the furnace will come on and heat up to the degree set on my thermostat, then the pilot light will go out and the furnace will ...
4
votes
3answers
109k views

How to wire multiple thermostats

I would like to have two thermostats controlling a single furnace. However I'm not 100% sure how I would need to wire everything to achieve the correct effect. Assuming a thermostat simply acts like ...
4
votes
2answers
278k views

How can I test whether my furnace issue is the limit switch or the thermostat?

I suspected this issue during the winter and confirmed it now in the summer. Regardless of the temp in my home, the blower motor runs non-stop. In the winter this must have been causing my home to got ...
4
votes
6answers
20k views

Why would a furnace overheat with a standard density filter?

Some time ago I found my furnace (gas, forced air, downdraft) was getting stuck on, blowing cold air. I could reset it, but it would happen again after a while. After calling out a service man, I ...
4
votes
7answers
9k views

What should I do with old furnace filters? [closed]

I seem to be stock piling used furnace filters, are there any uses for these things once the furnace is done with them? It seems a shame to throw them out; given that I change them once a month, ...
4
votes
2answers
13k views

Should my thermostat's blue wire be going to W2?

I've recently moved into my first house and am looking to replace the existing basic thermostat in the home. Here is a picture of how I found it wired: Researching the wires, I've read that commonly ...
4
votes
1answer
8k 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
23k views

Why won't my furnace turn off?

My furnace is running OK and heating the house. The problem is that I have the thermostat set to 66°F and it does not turn off when it reaches that temperature. I can turn it off manually at the ...
4
votes
2answers
1k 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 outside....
4
votes
3answers
23k 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
2answers
35k views

How can I determine why my furnace is not blowing enough heat?

During a cold spell last week when temperatures got down to -23f (-31C) my furnace started showing issues with blowing enough air and the air was not very warm. Last winter it did not have any issues ...
4
votes
1answer
2k views

How bad is it to attach a gas water heater to a gas furnace electrical circuit?

I'm looking to replace my existing water heater with a more efficient model. One of the things that makes better models more efficient is the replacement of the thermocouple / pilot control system ...
4
votes
4answers
4k views

Is it alright to run furnace and turn off gas?

Is running a furnace with the gas pipe shut can cause any harm to furnace?
4
votes
2answers
24k views

Can a washer and dryer be next to a water heater?

I have a GE gas dryer (DSXH47GGWW) that is currently next to an exterior basement wall. I'd like to move it to the opposite wall (shared with the crawl space) right next to the water heater next to ...
4
votes
2answers
687 views

Working furnace but smell like electrical fire

My furnace started to smell electrical fire once in awhile (not consistent). I guess it happens when we run the heat for a long time (many continuous days during cold weather). However, the furnace ...