RG3606 – RETURN GRILLE (36″W x 6″T)

Return air grille, 36 in. wide by 6 in. tall. Covers a return opening and passes air back to the system; the long, shallow proportion suits high wall, toe-kick and soffit returns where height is limited. No filter frame – pair with a filter at the air handler.

Specifications from our own stock records. The manufacturer does not publish a public page for this item.

Specs

• TypeReturn air grille
• Width36 in.
• Height6 in.
• Nominal Size36 x 6
• FunctionReturn air, no integral filter frame
• ApplicationWall or ceiling return air opening

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• 1RA3606WH
• 1703606

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

Which dimension do I order by?

The duct opening, always. A register or grille is sized to the hole it covers, and the outside flange runs bigger to hold it in place. A Hart and Cooley 12x6 sidewall register fits a 12x6 wall opening and measures 13-5/8 by 7-5/8 on the face. Measure the opening, or bring the old one in with you, and give us that number - not what you read across the face.

What do throw and spread mean?

Throw is how far the air stream carries before it slows down to nothing useful. Spread is how wide it fans out. You want throw that reaches the exterior wall and washes the window, because that is where the heat is coming in, and adjustable-blade bar registers let you set the spread. Supply face velocity of roughly 500 to 800 fpm is the working range, with about 700 a common target. Push much past that and you can hear it.

How big does a return grille have to be?

Bigger than what is probably up there now. Design for 400 CFM per ton with return static under 0.08 inches of water column, and hold return face velocity to 400 to 600 fpm, or 300 to 450 fpm on a filter grille. A 20x20 return is 400 square inches gross, but a stamped face is only about 70 percent free area, so call it 280 net - about 2 tons of air. Plenty of 3 and 4 ton houses around here breathe through exactly that one grille.

So the return is usually the real problem?

Usually. ACCA cites studies putting 80 percent of homes on undersized return duct systems. High static starves the coil, and in DFW that shows up as weak cooling in August, a sweating plenum, and a system that never delivers full capacity on a perfectly correct charge.