Air return size, is it suppose to be equal to vented air?

I did a quick math on my Furnace. Even when adding the air exchange vents, the air return is not even close to the same as what is fed in the floor vents and such. if I'm generous it may be 3:2 ~ out:return

I'd also like your opinion on if this should be replaced for efficiency? Furnace is a late 1980 wood/electric Newmac.

Reply to
cln
Loading thread data ...

Return air surface area should be like 125% of total output surface area - more if the return path is long .

Reply to
Terry Coombs

^^thanks Terry

Wow, I'm surprised my ducting hasn't buckled! I will add some returns in th e basement since there's only 1 for the Air Exchange (4"). The kids bedroom s are also a bit cold so I might add some returns there as the hallway air return doesn't seem to be enough.

(found my scrap paper; Rough measurement is 527sq hot air supply and 331sq for return)

Reply to
cln

IDK that it's a simple as that, ie that the intake area should equal the output. There are more outputs because the heat/cooling needs to be delivered to certain areas, while the return air intake locations can be fewer and are not as critical. To deliver air to all those places requires at least minium size ducts and registers. So, I would not be surprised that the outputs would add up to more than the intake. If there is some guideline, I've never heard it. The important thing is that there is sufficient duct capacity for the blower size. If you meet that on the intake and output, not sure that it makes a lot of difference if you have extra outputs. Whether you meet it or not can be determined by calculation or measured by pressure drop.

Reply to
trader_4

formatting link

Reply to
Taxed and Spent

the basement since there's only 1 for the Air Exchange (4"). The kids bedro oms are also a bit cold so I might add some returns there as the hallway ai r return doesn't seem to be enough.

What kind of basement? Finished or un?

AFAIK they don't usually put returns in an unfinished basement due to dust and typically colder air. (I could be wrong, but that was my understanding. )

Reply to
DerbyDad03

Our plan is to finish the basement, but valid point.

[Taxed and Spent , thank for the link]
Reply to
cln

IIRC there is also some rule about the return not being placed in line of sight of gas burning equipment, e.g. furnace, boiler, WH, etc.

If you finish the basement and build a utility closet, there should not be a return in that closet.

There are quite a few HVAC's forums that you could browse for more info. Just be sure that the info is up to date. Some forum posts might be outdated with regard to "what was standard at that time" and also code.

Reply to
DerbyDad03

One way to balance the heat around the house is to partly close the vents in some rooms while keeping the others wide open. Doing that, the ratio just changed.

What is important is having enough opening both in and out to handle the capacity of the blower so it is not restricted.

As for replacing a 36 year old furnace, good chance you will save money over time. You'd have to do some comparisons to see if it makes sense. My oil fired boiler was in need of repair and possible replacement so upgrading was an easy decision. Payback is about 7 years for me.

Reply to
Ed Pawlowski

I've always worked with the goal of 150%

Reply to
clare

There is a good chance your newmac is oversized for your application, but if you are burning wood the efficiency is not as much of a "killer" as if you are using electricity - and even thern it depends where you are and what you pay for electricity. Here in Ontario you don't want to be heating with electricity if there is ANY option. Burning $5 bills would be about the only way to heat that would cost more than electricity here.

Reply to
clare

All vents are fully open except the 'too hot master bathroom'.

I should call in a professional...............again

We just installed a ductless heat pump, this will be our first winter with it so I'll play it by ear. It also came in handy having it on hooked on the generator panel last week when the power was out.

I think at this point, investing in more attic insulation and improving other cold spots (bay area) would be a better investment.

Good point. also, if it ain't broken...

Reply to
cln

Well, until it's finished and used, you don't want to be putting returns down there. Even worse, with a return and no outlets in an unfinished basement, it will pull air from outside, interfere with any gas water heater venting, furnace venting, etc.

Reply to
trader_4

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.