2’’ CENTERS - PER SQUARE FT REQ 36 BTU’S OR ROLLERS
4” CENTERS - PER SQUARE FT REQ 9 BTU’S OR ROLLERS
6” CENTERS - PER SQUARE FT REQ 4 BTU’S OR ROLLERS
8” CENTERS - PER SQUARE FT REQ 2.25 BTU’S OR ROLLERS
10” CENTERS - PER SQUARE FT REQ 1.44 BTU’S OR ROLLERS
12’’ CENTERS - PER SQUARE FT REQ 1 BTU OR ROLLER
14’’ CENTERS - PER SQUARE FT REQ .735 BTU OR ROLLER
16’’ CENTERS - PER SQUARE FT REQ .5225 BTU OR ROLLER