Direct Exhaust - Boiler Room Air Openings - Weil-McLain SlimFit Manual

SlimFit
™
commercial condensing gas
DIRECT EXHAUST — Boiler room air openings
Combustion air provision
The SlimFit Commercial boiler can use inside air if no contaminants
are present in the boiler space. (If contaminants are likely to be pres-
ent, 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 29, page 35, selecting the appropriate installation condi-
tions.
Air openings must be sized to handle all appliances
and air movers (exhaust fans, etc.) using the air supply.
The sizing given in Figure 29, page 35 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
SlimFit boiler.
The SlimFit 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 29, page 35 will allow ad-
equate 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
installed louvers or grilles . Be sure to consider this reduction when
sizing the air openings.
34
-
fired water boiler
after reduction for any
— Boiler Manual
Special considerations
Tight construction
ANSI Z223.1 defines unusually tight construction where:
1. 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 . . .
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 plumb-
ing, 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 29,
page 35 if appliances are to use inside air for combustion and ventila-
tion.
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 ap-
pliances, but also to handle the air movement rate of the exhaust fans
or air movers using air from the building or space.
Combustion air damper interlock
If the air openings are fitted with motorized dampers, electrically
interlock the dampers to:
• Prevent the boiler from firing if the dampers are not fully open.
• Shut the boiler down should the dampers close during boiler
operation.
External relay interlock option
Activate an external relay on call for boiler operation from any source
(space heating, DHW or other). Use one of the relay contacts to start
the combustion air damper. Wire the combustion air damper end
LCI
switch in the boiler's circuit (automatic reset devices).
Sola control interlock option
The Auxiliary 1 Pump function of the Sola control is factory preset
to use one of the pump outputs to start a combustion air damper if
the control is programmed to use Auxiliary 1. One of the control's
pump outputs must be available to use this option. See page 57 for
instructions. Wire the combustion air damper end switch in the boiler's
LCI
circuit (automatic reset limits).
Part number 550-100-116/0713