UTICA BOILERS UB90-50 Installation Manual page 24

4. Combustion air and vent piping lengths:
Boiler 2" PIPE MINIMUM
siZe
100
75 & 50
The first 5 feet of "TOTAL EQUIVALENT LENGTH" of vent
piping run must be CPVC:
The length of pipe is counted from the boiler jacket (air intake
pipe) or from vent tee (vent pipe) the termination is not
counted toward the "Total Equivalent Length".
For additional elbows, reduce the maximum vent length as
shown:
• 2" 90 degree elbow -1 ½ feet per additional elbow.
• 3" 90 degree elbow - 3 feet per additional elbow.
Example:
To add 2 additional 90 degree elbows to a 3" pipe for a 75 boiler.
Each elbow is 3 additional feet per 90 degree elbow for a total of 6 feet.
(1 elbow @ 3 feet + 1 elbow @ 3 feet = 6 additional feet of pipe)
The total additional pipe is then subtracted from the maximum allowable pipe length to give the new maximum length of 94
feet with 6, 90 degree elbows.
("TOTAL EQUIVALENT LENGTH"):
Original 100 feet max. - 6 feet for 2 additional elbows = new 94 feet maximum length.
5.
Combustion air and vent piping to be pitched back to boil-
er at minimum ¼" per foot from intake and vent terminals
so that all moisture in combustion air and vent piping
drains to boiler. Pipes must be pitched continuously with
no sags or low spots where moisture can accumulate and
block the flow of air or flue gas. Combustion air and vent
pipes must be airtight and watertight.
COMBUSTION AIR AND VENT PIPE
coMBUstioN air aND VeNt PiPiNG leNGtHs
2" PIPE MAXIMUM
VENTING
8 FEET
8 FEET
3" PIPE MINIMUM
VENTING"
21 FEET
26 FEET
24
3" PIPE MAXIMUM
VENTING
27 FEET
32 FEET
VENTING"
92 FEET
112 FEET