Direct Exhaust - Boiler Room Air Openings; Special Considerations - Weil-McLain Ultra Commercial Installation And Start-Up Manual

COMMERCIAL GAS
DIRECT EXHAUST — Boiler room air openings
Combustion air provision
The Ultra Commercial boiler can use inside air if no contaminants are
present in the boiler space. (If contaminants are likely to be present, install
the boiler as a direct vent appliance, using the appropriate vent instructions
in this manual.)
The boiler room must be fitted with combustion air openings large enough
to provide air for all appliances in the room. Use the following information
to size the openings. Ensure the installation complies with all applicable
codes and standards.
Sizing combustion 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 21, page 31, selecting the appropriate installation conditions.
Air openings must be sized to handle all appliances and air
movers (exhaust fans, etc.) using the air supply.
The sizing given in Figure 21, page 31 is based on the National Fuel Gas
Code, ANSI Z223.1, allowing adequate air openings for gravity-vented gas
appliances (Category I) in addition to that needed for the Ultra boiler.
The Ultra Commercial boiler is rated Category IV (pressurized vent), and
has varying requirements for combustion and ventilation air, reflected by
the special sizing instructions given in in this manual.
The air openings recommended in Figure 21, page 31 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.
Free area — louver allowance
The free area of openings means the area
. Be sure to consider this reduction when sizing the air
louvers or grilles
openings.
30
-
FIRED WATER BOILER
after reduction for any installed
— Boiler Manual

Special considerations

Tight construction
ANSI Z223.1 defines unusually tight construction
where:
1. Walls and ceilings exposed to the outside atmo-
sphere have a continuous water vapor retarder with
a rating of 1 perm or less with openings gasketed,
and . . .
2. Weather-stripping has been added on openable
windows and doors, and . . .
3. 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 21, page 31 if appliances are
to use inside air for combustion and ventilation.
Exhaust fans and air movers
The appliance space must never be under a negative
pressure unless all appliances are installed as direct
vent. Always provide air openings sized not only to
the dimensions required for the firing rate of all appli-
ances, 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 dur-
ing boiler operation.
To accomplish this interlock, wire an
(proving the damper open) in series with the thermo-
stat input to the boiler. The boiler will not start if this
contact is open, and will shut down should it open
during operation.
isolated contact
Part number 550-100-086/0809