Need Another Return, But Where?

[Florida Joy]

according to what you wrote...and please correct me if I'm wrong..the current r/a
is on the opposite end of the house from master bedroom & general living area?

That is correct.

things like jump ducts and/or transfer grills will help to return air from master..
how many supplies in the master area?

Each room and each bathroom has one ceiling supply, with the exception of the family room, which has two wall supplies way up high. Open beam ceiling (only iso-board insulation between tongue & groove beams and roof sheathing) in the family room, so these supplies come into the room from the interior wall that abuts the attic space.

your ahu closet would have to be pretty big to allow a return duct to be put from
return on bottom, to besides the equipment..and back into attic to terminate at
new location. do you have that kind of room?.

See pix. I'm told the new return duct would be beside the ahu... through a new hole to be cut in top of stand... up through the ceiling. There's about 8.5 inches to the right of the ahu for such a duct, since the new ahu will be exactly the same footprint as the old one. Is that wide enough for a jumper duct?

will top of this closet be sealed air tight to attic when new trunk/supply plenum is installed?.

I would certainly expect that to be part of the contractor's job when installing the new ahu/new return duct!

[catmanacman]

i would just cut a return in where the coat rack and shoes are , if the supply ducts are sized right and the doors are undercut enough you should be fine

[Florida Joy]

i would just cut a return in where the coat rack and shoes are , if the supply ducts are sized right and the doors are undercut enough you should be fine

Thanks! That's been the plan from day one until one of the contractors came up with his idea of a return in the ceiling closer to the living areas at the "far end" of the house. Just needed a sanity check to see if having the second return in the foyer was a bad idea.

Is one 20x20 plus one 14x20 (680sq in total) enough return for a 3 ton?

[jtrammel]

It will work better than with just one but is not optimal, I use this rule of thumb sometimes total surface area x .8 x 2 so in your case it would be 680x.8x2 =1088cfm which is just over 2.5 tons of air, you need ~1200cfm.

[jtrammel]

It shouldn't be a problem to cut the studs and head them off carrying the load of the wall, without looking at it I can't say for sure that wall isn't load bearing but it most likely is not

[Florida Joy]

It will work better than with just one but is not optimal, I use this rule of thumb sometimes total surface area x .8 x 2 so in your case it would be 680x.8x2 =1088cfm which is just over 2.5 tons of air, you need ~1200cfm.

Here's what the Florida Building Code says about sizing returns:

SECTION M1403 HEAT PUMP EQUIPMENT

M1403.1 Heat pumps.
The minimum unobstructed total area of the outside and return air ducts or openings to a heat pump shall be not less than 6 square inches per 1,000 Btu/h (13 208 mm2/kW) output rating or as indicated by the conditions of the listing of the heat pump. Electric heat pumps shall conform to UL 1995.

[energy_rater_La]

seems to me it would be rather crowded to try to add addtl return duct
to what you have.
it may be best to use other side of r/a wall. 20x20 same as other side so
you only have one size filter to buy. (keep it simple)
cut studs use 2x4 framing of r/a filter grill to carry weight of wall..
once wall is determined not to be load bearing.

make sure that they mastic seal all your duct takeoffs on new trunkline,
and joints & seams of trunkline.

oh and pro's..
wow...anyone notice that furred down hallway??..oh to redo the
ducts and put them ALL inside the fur down...ducts in conditioned space...
wouldn't it be great!

best of luck OP!

[Florida Joy]

oh and pro's..
wow...anyone notice that furred down hallway??..oh to redo the
ducts and put them ALL inside the fur down...ducts in conditioned space...
wouldn't it be great!

I'm not sure what image you're looking at that makes you think the hallway is furred down. All the hallways have 8 ft ceilings with attic directly above, just like all the other 8 ft ceilings in the house. Perhaps the image showing the entry to the family room gives the illusion that the hallway is furred down because the open beam ceiling in that room is about 14 ft high and has no attic above.

[catmanacman]

aare you having a media filter installed at the unit ,if so a 20 x20 would be large enough if it does not have a filter in it

[Florida Joy]

aare you having a media filter installed at the unit ,if so a 20 x20 would be large enough if it does not have a filter in it

No... not enough space above the top of the ahu stand and the ceiling for a media filter. Eight foot ceilings are actually 94 inches above the floor... the top of the stand is 31 inches above the floor... the new ahu itself will be 60 inches, which allows for 3 inches of supply plenum up to ceiling level. The top of the 20x20 filter grille is 26 inches above the floor, so lowering the top of a 31 inch high ahu stand enough to accomodate an 8 inch high media filter cabinet without covering part of the filter grille would be quite a feat!

[jtrammel]

Here's what the Florida Building Code says about sizing returns:

SECTION M1403 HEAT PUMP EQUIPMENT

M1403.1 Heat pumps.
The minimum unobstructed total area of the outside and return air ducts or openings to a heat pump shall be not less than 6 square inches per 1,000 Btu/h (13 208 mm2/kW) output rating or as indicated by the conditions of the listing of the heat pump. Electric heat pumps shall conform to UL 1995.

I believe that code is referencing combustion air not return air for the air distribution system.