The weight of the vent stack or chimney must not rest on heater draft hood. Support must be provided in compliance with applicable codes. The heater top and draft hood must be readily removable for maintenance and inspection. Vent pipe should be adequately sup- ported to maintain proper clearances from combustible construction.
Type "B" double wall or equivalent vent pipe is recom- mended. However single wall metal vent pipe may be used as specified in the latest edition of the National Flue Gas Code ANSI Z223.1.
Common Vents
Manifolds that connect more than one heater to a com- mon chimney must be sized to handle the combined load. Consult available guides for proper sizing of the manifold and the chimney. At no time should the area be less than the area of the largest outlet.
10' OR LESS
VENT CAP
2' MIN
2' MIN
Drafthood
5' MIN
Heater
VENT PIPE
DRAFT HOOD 
HEATER 
Fig. 10: Venting Minimum Clearances
WARNING: These heaters must not be connected into any portion of mechanical draft systems operating under positive pressure. To do so may cause the flue products to be discharged into the living space causing serious health injury.
For connections to gas vents or chimneys, vent instal- lations shall be in accordance with Part 7, Venting of Equipment, of the National Fuel Gas Code, ANSI Z223.1, or applicable provisions of the local building codes.
Fig. 11: Common Venting
At the time of removal of an existing heater, the follow- ing steps shall be followed with each appliance remaining connected to the common venting system placed in operation, while the other appliances remain- ing connected to the common venting system are not in operation.
(a)Seal any unused openings in the common venting system.
(b)Visually inspect the venting system for proper size and horizontal pitch and determine there is no blockage or restriction, leakage, corrosion and other deficiencies which could cause an unsafe condition.
(c)Insofar as is practical, close all building doors and windows and all doors between the space in which the appliances remaining connected to the com- mon venting system are located and other spaces of the building. Turn on clothes dryers and any appliance not connected to the common venting system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will oper-
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