GWS
Gas-Fired Water Boilers –
Boiler Manual
6
Part Number 550-110-732/0703
Air openings
Using inside air — direct exhaust venting
The GWS boiler can use inside air if no contaminants are present
in the boiler space. If contaminants are likely to be present, install
the GWS boiler as a direct vent appliance, using the appropriate
instructions in the GWS Venting Manual and the instructions in this
manual.
Using outside air — direct venting
Combustion air can be ducted directly from outside to the GWS
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 (as well as combustion air) to
prevent overheating of the boiler controls and boiler space. Air is
also needed for other appliances located in the same space.
Use Figure 2, page 7, selecting the appropriate installation conditions.
Note that the sizing given in Figure 2 applies only to GWS
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
