Add a return grill near a supply grill?

[central nj]

Hi,

I have a beast of a room, 450 sq ft, 14 foot ceilings. 4 supply grills on the floor, and an inadequate double return, placed 10 foot high.

I would love to add more return flow. The only way I can see it (without tearing up drywall), would be to use the minfridge/closet that is 1 foot off the ground. I would be easy to have someone attach a return duct to it, and put a grill on the closet door. The problem is the return would be at floor level, about 9 feet from a floor supply. The supply grill feels like it blows straight up, and I also have a ceiling fan on low, 24/7. In short--the supply is very close, but at least not pouring air directly where the return would be sucking in air.

Would a floor return significantly disrupt airflow/ be a terrible idea?

Thanks,

Steve

[George2]

It would not disrupt the airflow.

Why do you feel that you need more RA. Do you think you need more to that room or just more RA overall?

[central nj]

Thanks for the post. If I described the inadequate return of my system it would move you to tears. I need 2000 cfm apparently, and have 3 crappy sources.

If it wouldn't disrupt the airflow, I wonder why they fairly competent fellow who saw it (and will eventually do the work) was so against it. We talked about increasing the 2 8-inch ducts servicing the double return, increasing them to 10 inches (but it wouldn't increase the grill or the part of the duct in the wall). When I told him about my idea around the minifridge he didn't like it.

Steve

[George2]

Thanks for the post. If I described the inadequate return of my system it would move you to tears. I need 2000 cfm apparently, and have 3 crappy sources.

If it wouldn't disrupt the airflow, I wonder why they fairly competent fellow who saw it (and will eventually do the work) was so against it. We talked about increasing the 2 8-inch ducts servicing the double return, increasing them to 10 inches (but it wouldn't increase the grill or the part of the duct in the wall). When I told him about my idea around the minifridge he didn't like it.

Steve

I've been doing this HVAC "thing" for more than 30 years. From installs to sales. I would like to think that I have seen it all, but I'm sure there are some "new" crappy stuff going on since I've gotten out.

You're right on........changing the 8" to 10" won't help much. Adding a RA, as you discribed, makes more sense. I would recommend, if that is the only place available, to go with a floor RA grille under the mini-fridge (if the MF is elevated, of course). They will allow much more airflow than a standard wall cavity or two.
Or, if you have a new house that has a "open" floor plan, you can put the RA anywhere. Even in the basement.

[Eddie1KRR]

When you say 3 crappy sources, is the third source at least a substantial one or the same as the 2 8" runs in this room?
Also, how well opened up is this room to the rest of the house? (big 8' or more openings?)

Is this room problematic in the winter as well?

[central nj]

George2--thank you!!
Eddie:

4 return Grills:

9x30 inch grill with 2 8-inch ducts

9x30 inch grill
2 8x15 inch grills
These three with a common 12x15 duct

A big open floor plan.

Any help would be appreciated.

Steve

[central nj]

Eddie--there is no problem in winter, or really any time. The house is comfortable. I'm interested in making the system more efficient and appropriate.

[Eddie1KRR]

Without seeing the house first hand, it's real hard to access online. But, from what you said so far, you do seem to be short on return air best I can tell.
George is correct on what he said. Changing only part of the duct is not going to help much if at all.

By my standards, your ductwork on the return side do not add up to the 2000 cfm you say you say your system is calling for. As far as your guy not loving the idea....That's hard to say why, he may be seeing some things that make that idea very challenging down below and have other ideas for getting air back to the furnace, so try and keep an open mind.

Glad to hear the system is working well as it is, at least it's not an emergency. You have time to do some research.

For that large room, with the high ceilings, check the rotation on that fan, no point in blowing hot air back down. Attic ventilators may help you out a bit there. Your HVAC contractor should be able to help you out there as well if you don't have one already

[George2]

George2--thank you!!
Eddie:

4 return Grills:

9x30 inch grill with 2 8-inch ducts

9x30 inch grill
2 8x15 inch grills
These three with a common 12x15 duct

A big open floor plan.

Any help would be appreciated.

Steve

The size of the grille(s) doesn't matter (per say), it's the "feed" that counts. If your walls are the standard 2x4 then "that" is the real amount of air you'll be getting back to the furnace.

I've never seen grilles that size. I think they are 30x8 and 6x14 or about 2 tons short of RA.

[second opinion]

The size of the grille(s) doesn't matter (per say), it's the "feed" that counts. If your walls are the standard 2x4 then "that" is the real amount of air you'll be getting back to the furnace.

I've never seen grilles that size. I think they are 30x8 and 6x14 or about 2 tons short of RA.

The mains alone are a little over two tons short

[central nj]

As I said, ...to cry.

Any problems putting the new return near the floor?

Would a single grill (6x14 or close to it) with a 10 inch round duct be enough?

[second opinion]

The ten inch will give you an additional 325 cfm increase it to a 14 inch will allow 750 and then change one of the others. The location of the return will not be a problem

[central nj]

George2--thanks again.

Second opinion--big big thanks. I looked, and between the rafters a 12x12 square would fit, which i see would be close to 700. I'll increase the 2-8inches to 10s for a little bit more, and call it a day.

This forum is wonderful!
Steve

[second opinion]

Adequate return and your good to go

[hvacvegas]

"I have a beast of a room, 450 sq ft, 14 foot ceilings. 4 supply grills on the floor, and an inadequate double return, placed 10 foot high.
"

You have a 5 ton system for a 450sqft space???
Is it a green house? Or is it located on the sun?
4 supply grills for a 5 ton system? Those must be some big registers.


I added a return to a similar system. 4 Ton system, open finished attic. Air handler pulls return from 25' away on a far interior wall, supply blows right out of air handler. Went through blower motors on a yearly basis. We refused to warranty any replaced parts untill return is taken care of.
Added a return, 4' under the supply. System works better, haven't replaced a motor in 5 years. Not the "best" solution, but it was the only solution, and atleast he doesn't have to replace the blower every summer.

[central nj]

hvacvegas--no it's just one of many rooms, part of a zone, for the 5 ton system. I'm just desperate to find more return air, and this bit under the cabinet seems like the most plausible. It is a big open floor plan, so i guess it will pull air from other rooms. There is slate floor through much of the rest of the house, and i think interior walls are over the slate. I am just not confident someone could drill/cut into it to get return from another area. This minifridge/cabinet is resting right over the air handler, over ?plywood, seems like they could connect it easily.

Do you think the plan (return near the supply/ceiling fan etc.) is ok?

Steve

[motoguy128]

"beast of a room" is relative. I hav a master bedroom suits that's around 650sqft. It only has 4 supply registers and 2 returns, but only needs about 1 ton of cooling for that total space. A simlar space downstairs is semi open and around 800sqft. IT also only needs about 1 ton.


As mentioned, you either have enough return or you don't. Location isn't that critical... at least not compared to supplies. If a supply has good throw, the best location for a return may actually be almsot adjacent to the supply.

[second opinion]

hvacvegas--no it's just one of many rooms, part of a zone, for the 5 ton system. I'm just desperate to find more return air, and this bit under the cabinet seems like the most plausible. It is a big open floor plan, so i guess it will pull air from other rooms. There is slate floor through much of the rest of the house, and i think interior walls are over the slate. I am just not confident someone could drill/cut into it to get return from another area. This minifridge/cabinet is resting right over the air handler, over ?plywood, seems like they could connect it easily.

Do you think the plan (return near the supply/ceiling fan etc.) is ok?

Steve

A diamond saw will cut through it like butter.

[central nj]

Ok, thanks again all. Very Very helpful info.

In my limited experience of trying to pop a tiny hole in floor for an ethernet cable, even after marking it, measuring it from somthing known, etc., thinking I was so smart. When i drilled the hole underneath, it was in the wrong spot when i came upstair to check it. I have visions of the diamond saw 12x12 inch hole cutting into a rafter or the other way cutting into the side of an interior wall. Having a pro do it obviously, but still a tiny risk. If my minifridge path really isn't a problem (which everyone now is saying it isn't), i guess i will go that way.

A+++ help. Thanks.
Steve