Technical information

A. O. Smith Water Products Company Service Handbook

Irving, Texas 2000©

Training Department

MAKE-UP AIR

HORIZONTAL DUCTS

When the heater is installed in an interior room with no roof access for vertical ducts, horizontal make-up

ducts should be installed. When using horizontal ducts, two openings are required - within

12 inches (30 cm.) of the top of the enclosure and one within 12 inches (30 cm.) of the bottom of the enclo-

sure. Each opening shall have a free area of not less than 1 square inch per 2000 BTUH of the total input of all

appliances within the enclosure.

Fresh AirFresh Air

Fresh Air

Fresh AirFresh Air

Fresh Air