Ventilation Air - Lochinvar Power-Fin Designer's Manual

Designer's Guide / Power-fin Water Heater
Chapter 1 – Combustion and

Ventilation Air

Everybody's gotta breathe. Even water heaters need air. Air seems easy enough. You stand in
the equipment room and you breathe comfortably, don't you? Open a door. Open a window.
This is a big room. There's lots of air in here for the water heater.
The average person inhales 400 to 500 cubic feet of air in a 24 hour period. A one million Btu/hr
water heater will draw 226.38 cubic feet of air every MINUTE! A 20 by 20 by 8 foot equipment
room holds 3200 cubic feet of air. That's a volume of air to last you or me over six days. A one
million Btu/hr Power-fin will consume 3200 cubic feet of air in 14 minutes.
Therefore, a good, easy flow of clean air is 100% necessary for clean, efficient combustion. So,
we need to provide a permanent and uninterrupted flow of air to the water heater. The Power-fin
water heater is designed to receive combustion air by one of TWO methods. The water heater
may draw combustion air from the room or have the air ducted directly to the water heater from
an exterior space.
This chapter explains the methods for "air from the room".
Chapter 2 explains "air ducted directly to the water
heater". Again, this chapter lists several techniques to
size the air openings that will deliver room air. If there are
other appliances in the room requiring air, their air
requirements must be including when sizing the air
openings.
Provisions for combustion and ventilation air must be
designed and installed in accordance with "Air for
Combustion and Ventilation", of the latest edition of the National Fuel Gas Code, ANSI Z223.1, (in
Canada, the latest edition of CGA Standard B149 Installation Code for Gas Burning Appliances
and Equipment) or applicable provisions of the local building codes.
NEGATIVE PRESSURE IN THE EQUIPMENT ROOM
It is important to NEVER have a negative pressure on the equipment room. Exhaust fans are
popular in equipment rooms to exchange the air. If the exhaust fan pulls air OUT, then a negative
pressure occurs in the room. The combustion and ventilation air must be sized to supply all the
equipment PLUS the air for the exhaust fan.
COMBUSTION AND VENTILATION AIR SIZING CALCULATIONS
The sizing calculations in this section are based on "Free Area". The louvers or grill used on the
air openings must have a net free area equal to or greater than the value derived in the
calculations. The Free Area in a louver or grill is defined as the open, unblocked area. The
louvers, grills, mesh, blades, all will block a given amount of space in the louver's overall
dimension. Consult the louver manufacturer for exact net free area of the louver.
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LOCHINVAR CORPORATION
300 MADDOX SIMPSON PKWY
LEBANON, TN 37090
www.lochinvar.com
Air