Roberts Gorden NDUSTRIA NHE Series, Installation, Operation & Service Manual

Page: 48 / 78

NHE-S
ERIES
I
NSTALLATION
, O
PERATION AND
S
ERVICE
M
ANUAL
44
8.7 Unvented Operation Tube Termination
Turndown type vent terminal with a screen must be
installed at the exhaust end of the tube. Vent
terminal design shall not incorporate backdraft flap.
FIGURE 29: Tube Termination
8.8 Length Requirements
Minimum vent length allowed is 2' (.6 m). Maximum
vent length allowed is 45' (13.7 m). Maximum
outside air supply duct length allowed is 45' (13.7
m).
The total vent length, plus outside air duct length,
plus any extensions to minimum heat exchanger
lengths, cannot exceed 65' (19.8 m).
Vent length should be limited to less than 20' (6 m).
If using vent lengths greater than 20' (6 m),
condensation will form in the vent pipe. Insulation
and additional sealing measures (high temperature
silicone at all seams) are required. Optional heat
exchanger beyond minimum lengths is considered
as vent length for length determination.
Subtract 15' (4.6 m) of maximum allowed vent or
duct length per vent elbow if more than two are
used.
8.9 Vent Material Recommendations
Vent recommendations:
1. Porcelain coated tubing 4'' (10 cm) O.D.
(P/N 9141030D)
2. Heat treated aluminized tubing 4'' (10 cm) O.D.
(P/N 91409408)
Heat treated aluminized tubing 6'' (15 cm) O.D.
(P/N E0009105)
3. Single wall pipe (Type-C) that is corrosion resis -
tant galvanized steel - minimum 26 ga.
(Supplied by others)
4. Double wall vent (Type-B). For Category l vent -
ing only or used as a continuous section pass -
ing through the outside wall, roof or outside of
the building.
NOTE:
4" (10 cm) O.D. Porcelain coated tubing (P/N
914030D), 4" (10 cm) O.D. Heat treated aluminized
tubing (P/N 91409408), and 6" (15 cm) O.D. Heat
treated aluminized tubing (P/N E0009105) are
equivalent to single wall corrosion resistant flue pipe.