GWS-090E
Gas-Fired Water Boiler –
Boiler Manual
6
Part Number 550-110-737/1108
Air openings
Using outside air — direct venting
Combustion air can be ducted directly from outside to the GWS-
090E boiler air intake fitting. This method is defined as
direct vent
(also referred to as sealed combustion). Refer to the appropriate
instructions in the GWS Venting Manual and the instructions in
this manual. Two options are available: sidewall or vertical direct
vent. Each requires a special vent component kit.
Sizing air openings
Air openings provide for ventilation to prevent overheating of the
boiler controls and boiler space. Air is also needed for other ap
-
pliances located in the same space.
Use Figure 2, page 7, selecting the appropriate installation condi
-
tions. Note that the sizing given in Figure 2 applies only to GWS-
090E installations with clearances no smaller than shown in Table
1, page 3 of this manual. For smaller clearances, regardless of
how the air openings are arranged, two openings providing free
area of 1 square inch per 1,000 Btuh input of all appliances in
the space are required.
Air openings must be sized to handle all appliances
and air movers (exhaust fans, etc.) using the air
supply.
The sizing given in Figure 2 is based on the National Fuel Gas
Code, ANSI Z223.1, allowing adequate air opening for gravity-
vented gas appliances. The air openings recommended in Figure
2 will allow adequate ventilation and combustion air provided the
boiler room is not subjected to negative pressure due to exhaust
fans or other mechanical ventilation devices. Refer to the National
Fuel Gas Code for dealing with other conditions.
Louver allowance
The free area of openings means the area after reduction for any
installed louvers or grilles. Be sure to consider this reduction when
sizing the air openings.
Special considerations
Tight construction
ANSI Z223.1 defines unusually tight construction where:
a. Walls and ceilings exposed to the outside atmosphere have
a continuous water vapor retarder with a rating of 1 perm or
less with openings gasketed, and . . .
b. Weather-stripping has been added on openable windows and
doors, and . . .
c. Caulking or sealants are applied to areas such as joints
around windows and door frames, between sole plates and
floors, between wall-ceiling joints, between wall panels, at
penetrations for plumbing, electrical, and gas lines, and in
other openings.
For buildings with such construction, provide air openings into
the building from outside, sized per the appropriate case in
Figure 2.
Exhaust fans and air movers
The appliance space must never be under a negative pressure,
unless the appliances are installed as direct vent. Always provide
air openings sized not only to the dimensions required for the
firing rate of all appliances, but also to handle the air movement
rate of the exhaust fans or air movers using air from the building
or space.
Motorized air dampers
If the air openings are fitted with motorized dampers, electrically
interlock the damper to:
• Prevent the boiler from firing if the damper is not fully open.
• Shut the boiler down should the damper close during boiler
operation.
To accomplish this interlock, wire an isolated contact (proving the
damper open) in series with the thermostat input to the boiler.
The boiler will not start if this contact is open, and will shut down
should it open during operation.
1 Prepare boiler location
continued
