Weil-McLain GOLD CGs - Manual (Page 12)

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Part Number 550-141-873/0502 12
8. Verify vent system length
The vent or air piping must be no longer than the
maximum value given in
Tables 4 and 5 . Note in the
tables that the maximum length of connector piping
(vent or air piping between boiler and B-vent tee
connection) depends on the number of elbows and the
length of the B-vent section. The reason for this is that
each 90-degree vent or air pipe elbow cause the same
pressure drop as 7 feet of straight pipe.
Vent/air piping length verification
procedure:
Step 1 — Determine dimensions of vent/air pipe
needed for planned location
Measure or calculate the vent/air pipe lengths required
for the planned location of the boiler and floor/roof
penetrations. See
Figure 11 for a typical layout.
• How long will the vertical B-vent section have to be?
Round up to the nearest 5 feet (for example, if B-vent
length needs to be 12 feet, round this amount up to the
nearest 5 feet — use 15 feet for your B-vent length).
(This is dimension L in Figure 11.)
• How many elbows will be needed in the vent connector
piping (from boiler to B-vent tee)?
• How many feet of vent piping will be needed for the
connector runs?
(This would be the sum of dimensions C & D in Fig. 11.)
• How many elbows will be needed in the air connector
piping (from boiler to B-vent tee)?
• How many feet of air piping will be needed for the
connector runs?
(This would be the sum of dimensions A & B in Fig. 11.)
Step 2 — Verify that vent connector piping is within
allowable limits
Use Table 4 or 5 , depending on boiler model to be used.
Find the row with the B-vent length the installation
requires. Move across to the column with the number
of vent elbows needed for the installation. This number
is the maximum allowable vent connector piping length.
Step 3 — Verify that air connector piping is within
allowable limits
Use Table 4 or 5 , depending on boiler model to be used.
Find the row with the B-vent length the installation
requires. Move across to the column with the number
of air pipe elbows needed for the installation. This
number is the maximum allowable air pipe connector
piping length.
Example verification (Figure 11 Figure 11 Figure 11 Figure 11 Figure 11):
Step 1 — Vent/air piping required per plan
As an example, consider an installation of a CGs-5
boiler, where the boiler and vent/air locations would
require:
•
Boiler model = CGs-5.
• B-vent length ( L ) = 20 feet .
• Vent connector piping requires 2 elbows .
• Vent connector piping length ( D + C ) = 16 feet .
• Air connector piping requires 1 elbow .
• Air connector piping length ( B + A ) = 17 feet .
Step 2 — Verify vent piping
• Enter Table 5 at the row for B-vent length of 20
feet.
• Move to the 2-elbow column.
• Read a maximum connector pipe length of 18 feet .
Conclusion — Vent piping is within limits because
vent connector piping would only be 16 feet (less than
the maximum of 18 feet).
Step 3 — Verify air piping
• Enter Table 5 at the row for B-vent length of 20
feet.
• Move to the 1-elbow column.
• Read a maximum connector pipe length of 25 feet .
Conclusion — Air piping is within limits because air
connector piping would only be 17 feet (less than the
maximum of 25 feet).
Step 4 — Replanning
No replanning needed. Vent and air piping lengths are
within limits.
Step 4 — Replan boiler location & piping if piping
length of vent or air is too long
See if boiler can be moved closer to vertical vent/air
piping.
See if you can reduce the number of elbows required
vent piping must have 2 elbows minimum in order to
provide horizontal piping to install condensate drain
tee.