33
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 XTherm heater is installed to replace
an existing heater, the vent system MUST be veri-
fied to be of the correct size and of Category IV UL
Listed stainless steel vent material construction. If it
is NOT, it MUST be replaced.
NOTE:
For extractor sizing, typical CO
2
levels are
9.7% for natural gas and 11.2% for propane gas and
flue temperature of 350°F, at 100% firing rate. mea-
sured at a test port, 12” above the flue collar.
* NOTE: Data for 100% firing rate.
Table P: Typical Vent Pressure and Volume
of Flue Products
Fig. 36: Typical Common Venting
Model
No.
Vent Size
(in.)
Vent Pressure
(in. WC)
Volume of
Flue Products
(CFM)
2505
10
0.2
800
3005
0.3
960
3505
0.3
1120
4005
12
0.3
1280
VENT CAPS STACKED VERTICALLY
FLUE GASES MOVING IN PARALLEL
VENT CAPS ALL AT SAME ELEVATION
FLUE GASES MOVING TOWARD EACH OTHER
VENT CAPS AT STAGGERED ELEVATIONS
FLUE GASES MOVING TOWARD EACH OTHER
1” MINIMUM (TYP)
2” MINIMUM (TYP)
1” MINIMUM (TYP)
DISCHARGE
4’-0” MIN.
(TYP)
4’-0” MIN.
(TYP)
DISCHARGE
Fig. 35: Sidewall Vent Cap Configurations