SERVICE TECHNICIAN ONLY — read and follow completely.
Figure 24 Flue pipe clearances Figure 25 Back vent clearances
Figure 26 Top vent clearances
Type “L” double-wall
vent piping
Combustible surface
Protection
Type “L”
double-wall
vent pipe
6"
A
6"
24" For servicing
or min. 2" For close
clearances
Combustible
surface
Combustible
surface
A
A
2"
Note: 2" min. on sides
Table 5 Protection required for clearances
less than 6 inches from doublewall
vent pipe*
Dimension A
When desired minimum
clearance from
Type “L” double-wall
vent pipe to combustible
surface is:
Use the following
protection**:
3"
½” thick insulation board
***
over one-inch glass fiber
or mineral wool batts+
2"
24 gauge sheet metal with
one-inch ventilated air
space
3"
½” thick insulation board
***
with one-inch ventilated air
space
* All clearances measured from outer surface of
equipment to combustible surface, not to the
protection used.
** Apply to combustible surface unless otherwise
noted. Cover all surfaces as specified in Table and
Figure 24. Thicknesses are minimum.
*** Factory-fabricated board made of non-
combustible materials, normally fibers, having
thermal conductivity in range of one (Btu-inch)/
(hr./sq. ft./°F) or less.
+ Mineral wool batts (blanket or board), having min.
density of 8 lb/ft3 and a min. melting point of
1500°F.
Other dimensions available. Refer to NFPA-31.
Combustible
surface
Combustible
surface
A
A
Note: 2" min. on sides
2"
2"
24" For
servicing
or min. 2"
For close
clearances
Close clearance installation (continued)
Part number 550-141-826/1014
33
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WGO
OIL-FIRED NATURAL DRAFT WATER BOILER — SERIES 3 — Boiler Manual
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