32
Table O: Category IV Vertical Venting
* Special vent materials are still required.
** Subtract 10 ft per elbow. Max. 4 elbows.
1
Requires D-33 Poly vent adapter/limit kit.
Termination
The vent terminal should be vertical and should ter-
mi-nate outside the building at least 2 ft above the
highest point of the roof that is within 8 ft for models
2505 through 3505 and 10ft for model 4005. The vent
cap should have a minimum clearance of 4 ft horizon-
tally 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 pub-
lic walkways, adjacent buildings, open windows and
building openings must be consistent with the NFGC
(U.S.) or B149 (Canada). Gas vents supported only by
flashing and extended above the roof more than 5 ft
should be securely guyed or braced to withstand snow
and wind loads.
Common Venting
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 P provides boiler discharge vent
pressures at vent pressure switch and volumes of flue
products at full fire for the calculation of appropriate
vent and extractor sizing for common venting.
Raypak does not support common venting under
positive-pressure conditions. Use a variable-speed
extractor to draw the stack to negative pressure. See
Fig. 36.
2505 THRU 3505
4005
Fig. 34: Vertical Venting
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 building.
Model
No.
Certified Vent
Material*
Vent Size
(in.)
Total Vent Height
(eq. ft.)**
Combustion
Air Intake Pipe
Material
Air Inlet
Max Length** (eq. ft.)
Min.
Max.
10” Ø
12” Ø
2505
Stainless Steel
Category IV
(UL listed),
Centrotherm
Polypropylene
1
10
5
100’
Galvanized
Steel,
PVC, ABS,
CPVC
100
N/A
3005
3505
70’
N/A
100
4005
12
100’
