28
UH
Series
Figure 3.8
•
General Vent Requirements
When possible, avoid venting through an unconditioned space. Venting through an unconditioned space
promotes condensation. When venting through an unconditioned space is unavoidable, or if the unit is
installed in an area that is prone to condensation, insulate venting runs greater than 5 feet to minimize the
production of condensation. Inspect for leakage prior to insulating the venting and only use insulation that
is non-combustible with a temperature rating of not less than 400°F. Install a tee fitting at the low point of
the vent system and provide a drip leg with a clean out cap as shown in Figure 3.8.
When venting pipe passes through a combustible interior wall or floor, a metal thimble with a diameter 4
inches greater than the vent pipe diameter must be used. If there is 6 feet or more of vent pipe prior to
passing through the combustible wall or floor, then the metal thimble need only be 2 inches greater than
the vent pipe diameter. If a metal thimble is not used, all clearance to combustibles from the vent pipe
must be 6 inches. Where permitted, type B vent may be used for the last section of vent pipe to reduce
the required clearance to combustibles when passing through a combustible wall or floor. When using
type B venting, follow the manufacturer’s recommended clearance to combustibles. Any material used to
close or insulate the opening must be non-combustible.
3.0
Installation
•
General Venting Requirements
*Consult the NFPA ANSI Z223.1 Gas Vent Termination criteria if roof pitch exceeds 9:12
24 in.
Min.*
Double-Wall B Vent
Roof*
Heater
1 in. Minimum Clearance
1 in. Minimum Clearance
Fire Stop Spacer
#8 Sheet Metal Screws (field supplied)
Adjustable Roof Flashing
Storm Collar
B to C Adapter
Clean Out Tee Fitting
Vent Cap
Clean Out Cap
