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 Fuel Gas Code ANSI Z223.1.
Manifolds that connect more than one boiler 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
2' MIN
VENT PIPE 
VENT CAP
2' MIN
5' MIN
DRAFT HOOD 
HEATER 
Fig. 15: Common Venting
At the time of removal of an existing boiler, 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 make sure there is no blockage or restriction, leakage, corrosion and other deficiencies which could cause an unsafe condition.
(c)As much as possible, 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
Fig. 16: Venting Clearances
hoods and bathroom exhausts, so they will oper- ate at maximum speed. Do not operate a summer exhaust fan. Close fireplace dampers.
(d)Place in operation the appliance being inspected. Follow the lighting instructions. Adjust thermostat so appliance will operate continuously.
(e)Test for spillage at the drafthood relief opening after 5 minutes of main burner operation. Use the flame of a match or candle, or smoke from a ciga- rette, cigar or pipe.
(f)After it has been determined that each appliance remaining connected to the common venting sys- tem properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other gas burning appliance to their previous conditions of use.
(g)Any improper operation of the common venting system should be corrected so that the installation conforms with the latest edition of the National Fuel Gas Code, ANSI Z223.1. When
For special venting applications that require reduced vent sizes and
14
