C. ACCESSIBILITY CLEARANCES
1. The Series PFC
TM
boiler is certified for closet
installations with zero clearance to combustible
construction. In addition, it is design certified for use
on combustible floors. Do not install on carpeting.
2. Figure 1.1 shows the minimum recommended
clearances to allow reasonable access to the boiler for
inspection and maintenance. However, local codes or
special conditions may require greater clearances.
D. COMBUSTION & VENTILATION AIR
1. The Series PFC
TM
boiler is designed for operation
with combustion air piped directly to the boiler from
outside the building (sealed combustion). Combustion
air can be supplied from within the building only if
adequate combustion and ventilation air is provided
in accordance with the section of the National
Fuel Gas Code entitled, “Air for Combustion and
Ventilation” or applicable provisions of the local
building codes.
2. If the combustion air is piped directly to the boiler
from outside the building, no additional combustion
or ventilation air is required. Otherwise, follow
the National Fuel Gas Code recommendations
summarized in subsections 3 through 10.
3.
Required Combustion Air Volume
: The total
required volume of indoor air is to be the sum of the
required volumes for all appliances located within
the space. Rooms communicating directly with the
space in which the appliances are installed and
through combustion air openings sized as indicated
in Subsection 3 are considered part of the required
volume. The required volume of indoor air is to be
determined by one of two methods.
a.
Standard Method
: The minimum required volume
of indoor air (room volume) shall be 50 cubic feet
per 1000 BTU/Hr (4.8 m3/kW). This method is to
be used if the air infiltration rate is unknown or if
the rate of air infiltration is known to be greater
than 0.6 air changes per hour. As an option, this
method may be used if the air infiltration rate is
known to be between 0.6 and 0.4 air changes
per hour. If the air infiltration rate is known to be
below 0.4 then the
Known Air Infiltration Rate
Method
must be used. If the building in which this
appliance is to be installed is unusually tight, PB
Heat recommends that the air infiltration rate be
determined.
b.
Known Air Infiltration Rate Method
:
where:
I
fan
= Input of the fan assisted appliances
in Btu/hr
ACH = air change per hour (percent of the
volume of the space exchanged per
hour, expressed as a decimal)
Note: These calculations are not to be used for
infiltration rates greater than 0.60 ACH.
3
PREINSTALLATION
Figure 1.1: Minimum Accessibility Clearances – PFC-625 & PFC-750
24"
24"
24"
24"
15 ft
3
I
fan
ACH
1000
Btu
/
hr
Required Volume
fan
=
(
(
