S U F S E R V I C E H A N D B O O K
I N S T A L L A T I O N
MAKE-UP AIR
Direct Communication
A fresh supply of make-up air for combustion can be supplied to the heater through make-up air openings, which directly communicate with the out of doors. Two openings are required — one within 12 inches of the top of the enclosure and one within 12 inches of the bottom of the enclosure. Each opening shall have a free area of not less than 1 square inch per 4000 BTUH of the total input of all appliances within the enclosure.
The lower opening is primarily providing combustion air. The upper opening is providing vent dilu- tion air and acts as a relief opening for flue gases should the vent become obstructed or a down draft condition occur.
MAKE-UP AIR
Vertical Ducts
Often it is more practical to install vertical make-up air ducts to the outdoors. Again, 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 enclosure. Each opening shall have a free area of not less than 1 square inch per 4000 BTUH of the total input of all appliances within the enclosure.
Technical Training Department | 10 | State Water Heaters |
STC-077 | Ashland City, Tennessee © 2004 |
