building openings must be consistent with the NFGC
(U.S.) or B149 (Canada). Vents supported only by
flashing and extending above the roof more than 5 ft
should be securely guyed or braced to withstand snow
and wind loads.
Common Venting
Raypak does not support common venting under pos-
itive pressure. Variable-speed extractor fan must be
used to draw the stack to negative pressure. See Fig.
26.
The NFGC does not address sizing guidelines for the
common venting of multiple Category IV heaters. This
is covered in the NFGC under “Engineered Vent Sys-
tems”. Table O provides volumes of flue products at
full fire for the calculation of appropriate vent and
extractor sizing for common venting.
Termination
The vent terminal should be vertical and should termi-
nate outside the building at least 2 ft above the highest
point of the roof that is within 8 ft. The vent cap should
have a minimum clearance of 4 ft horizontally from and
in no case above or below (unless a 4 ft hori-zontal
distance is maintained) electric meters, gas meters,
regulators and relief equipment.
The distance of the vent terminal from adjacent public
walkways, adjacent buildings, open windows and
NOTE:
A vent adapter (field-supplied) may be re-
quired to connect the Category IV vent to the boiler.
CAUTION:
The condensate drain line must not be
allowed to freeze. Take appropriate measures.
WARNING:
Vent connectors serving any other
appliances shall not be connected into any portion of
mechanical draft systems operating under a positive
pressure. If an XFyre is installed to replace an exist-
ing unit, the vent system MUST be verified to be of
the correct size and of Category IV AL29-4C vent
material, approved PVC/CPVC construction, or
Centrotherm™ polypropylene (in Canada, ULC-
S636 approved plastic materials must be used). If it
is NOT, it MUST be replaced.
CAUTION:
The inlet water temperature to the
XFyre must not exceed 170ºF at any firing rate to
use the PVC venting option. The venting system
must conform to local codes and/or the current
National Fuel Gas Code ANSI Z223.1/NFPA 54. The
system setpoint must not exceed 180ºF.
CAUTION:
A listed vent cap terminal suitable for
connection to the Cat IV vent materials, adequately
sized, must be used to evacuate the flue products
from the boilers.
NOTE:
When using PVC “T” vent as termination,
insert the round stainless mesh screens provided
with the unit into the tee ends.
inch per linear foot from the heater to the vent termi-
nal. The horizontal portions of the vent shall also be
supported for the design and weight of the material
employed to maintain clearances and to prevent physi-
cal damage or separation of joints.
NOTE:
When
using
Centrotherm
™
Polypropylene “T” vent termination
, insert two
Centrotherm™ termination screens into the tee
ends.
30
WARNING:
An extractor is required when multiple
heaters are vented through a common vent pipe.
The extractor must operate when one or more units
are firing.
8’ OR LESS
Fig. 25: Vertical Venting
