Roberts Gorden NDUSTRIA NHE Series Installation, Operation & Service Manual page 47

For common vertical venting of more than two heaters, See Page 54, Section 9.
A vent shall not extend less than 2' (0.6m) above the highest point where it passes through a flat roof of a
building.
Note: Vertical venting will be classified as a Category lll if the length of the horizontal portion of the vent
pipe is greater than 75% of the vertical portion of the vent pipe. (Example: If vertical vent section of the vent
is 10' (3 m) long, the horizontal section of the vent is greater than 7' 6" (2.3 m) long.)
8.5 Vertical Venting (Category I) 4" (10 cm) Pipe
For Category I vertical venting guidance, refer to the National Fuel Gas Code (ANSI Z 223.1 , NFPA 54) in
the USA and CSA B149.1 code in Canada. Some rules that are applicable are listed below:
• A category I vent system is not required to be "gas tight" as the pressure inside the vertical vent system is
a negative pressure.
• Type B vent material is acceptable for use in the vertical venting configuration (See Page 48, Figure 8.13).
• The length of the horizontal portion of the vent pipe must be less than 75% of the vertical portion of the
vent pipe. (Example: If vertical vent section of the vent is 10' (3 m) long, the horizontal section of the vent
must not exceed 7' 6" (2.3 m) long.)
• Horizontal portion of the vent pipe can be double wall vent type-B or single-wall pipe type-C and have an
upward slope from the heater of at least 1/4" (.632 cm) per foot. When using type B-vent on horizontal
section, use B to C adapter (supplied by others) and attach to end of heater tube in place of supplied vent
adapter.
• The vertical vent must terminate at least 5 ft (1.5 m) above the vent connection to the unit.
Note: Horizontal Venting (Category I) is not a possible configuration with this product.
Common vertical venting (Category l) is not a possible configuration with this product.
8.6 Venting Category Designation by Model
Single Heater Horizontal
Model
Venting Category
NHE-40
NHE-60
NHE-80
NHE-100
NHE-125
NHE-150
NHE-175
* Vertical venting will be classified as a Category III if the length of the horizontal portion of vent pipe is greater than 75% of the
vertical portion of vent pipe. (Example: If vertical vent section of vent is 10' (3 m) long, the horizontal section of vent is greater than 7'
6" (2.3 m) long.)
III
III
III
III
III
III
III
Single Heater Vertical
Venting Category*
I
I
III
III
III
III
III
SECTION 8: V
Common Venting Category
(for both Vertical and Horizontal)
III
III
III
III
III
III
III
ENTING
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