Heating, Air Conditioning, Fridge, HVAC/AC Cold Air Return

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Question
Hi Jim,

I have a 2 ton Ream air handler in attic and outside compressor for my 1350 square foot brick raised ranch home. There is one return in the hallway on the western end of the home. The unit is 10 years old.

My personal bedroom and a second bedroom are on the western end of the brick house which is two stories of brick covering the exposed part of the basement and the 1st floor.

These two rooms on sunny days are always 5 or 6 degrees warmer than the temp in the livingroom where the thermostat is located. The end of my bedroom facing the west wall is 2 degrees warmer than the opposite end of the bedroom. My walls are insulated and there is 8 inches in the attic.

I notice the ceiling is very warm because when I turn on the ceiling fan the whole bedroom heats up. The flexible duct coming into this bedroom is 8 inches and a 24 foot run.

Since the return for the AC is in the hallway outside of the bedroom, I was wondering how putting a register in this bedroom ceiling and connecting it to the main return will improve the coolness of the bedroom?

How will that impact the cooling of the rest of the house?

Since the incoming air enters through an 8 inch diameter flexible duct, how large should the new return in the bedroom be in size? I would prefer to use a rectangular duct because it would be much easier for me to cut a rectangular hole into the insulated return in the attic than trying to cut a round hole. Correct?

Second question if I may:
I normally use a 20" square fiberglass see through filter in the AC return. This year I decided to try one of the accordion looking filters that blocks much more dust than the see through fiberglass filters. You can't see through the accordion filter.

How does using this accordion filter impact the AC unit and cooling of the home?

Many Thanks Jim!

Appreciatively Yours,

Mike

Answer
Mike,
Your AC system needs at least 200 square inches of free area for the return air to flow through from the return air grill face to the blower compartment inside.
A 20x20 filter is 400 square inches but it only lets 50% of air pass through it when it is brand new, each time the blower runs the filter picks up dust & dirt which reduces the free air supply more and more, If the return grill is a 20x20 grill
it also only lets 50% of that area air pass through.
At the ceiling filter grill in the hall you are at bare minimum,
From the filter grill to the air handler blower compartment you need at least a 20x10 duct un-obstructed with no other branches of duct tapped in.
In rooms/areas like bed rooms if there is no return air outlet in the room itself you can't condition it unless the door to the room is open.
In order to size what you need to cool a room you need to know what the area of exposed ceiling, floor, and walls is, plus windows, insulation sun, shade etc.
Adding a high return air into a bed room will help if it is placed properly and ducted all the way to the blower compartment of the air handler.
You can go in the attic, take the cover off of the blower compartment, rig the door safety switch so the blower gets power, set the thermostat to fan on and feel the air flow difference coming out of the bed room supply, also feel the air flow with the BR door open and closed and I think you'll get the idea.

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Jim Barnhart

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Fifty + years conditioning the air.

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Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

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Hands on since 1950

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