10
Cast Iron Condensing Boilers – Installation Manual
FlexCore Stainless Steel Condensing Boilers – Installation Manual
Figure 1 - Multiple Boiler Common Venting
VERTICAL CHIMNEY VENTING - Vertical venting -
multiple boiler installations:
It is recommended that the boiler nearest the
vertical chimney be fired first when the
horizontal distance exceeds 50% of the
vertical distance. Refer to the HeatNet
manual on how to select the lead boiler.
When sized for a (CAT II) configuration, a negative
pressure of 0.02 to 0.10 inches WC is required in each
boiler’s riser when all boilers are operating at full input.
A barometer damper must be installed as illustrated.
[Exception: if the vent system is designed using accepted
engineering practices, and the design calculations prove
there is no need for barometric dampers, the barometric
dampers may be omitted.] When required by applicable
codes, install a thermal spill switch on each barometric
damper.
1. Connect each boiler riser to the common vent with a
Y connection or Boot T only.
2. Install an approved vent cap at each vent termination.
3. Dimensions:
B = breeching length
C = chimney height
D = breeching diameter
F = riser diameter
(No smaller than the dimension given in Table 4,
page 6.)
4. Multi-story, common venting systems shall be in
accordance with the National Fuel Gas Code, ANSI
Z223.1/NFPA 54 and/ or the CSA B149.1, Natural Gas
and Propane Installation Code (Current Editions), local
codes and vent manufacturer's installation instructions.
Size the chimney and breeching using generally
accepted engineering practices. (Consult factory for
vertical heights beyond 60 ft.)
DOUBLE ACTING
BOILER #1
THERMAL SPILL
SWITCH
BOILER #2
FLUE VENT
(IF REQUIRED)
(IF REQUIRED)
BOILER #3
(IF REQUIRED)
BOILER #4
BAROMETRIC DAMPER
ALL CONNECTIONS
TO BE "T-WYE"
RIOM-0201_A
"B"
"D"
"C"
"F"
