U.S. Boiler Company PVG3, Installation, Operating And Service Instructions

12

g.  Minimum 10 feet (2 m) horizontally from an 

operable opening in an adjacent building.  This 

does not apply to vent terminals 2 feet (0.6 m) 

or more above or 25 feet (7.6 m) or more below 

operable openings.

9.  Enclose vent passing through occupied or 

unoccupied spaces above the boiler with material 

having a fire resistance rating of at least equal to the 

rating of the adjoining floor or ceiling.  Maintain 

minimum clearances to combustible materials.  See 

Figure 1.

  Note:  For one or two family dwellings, fire 

resistance rating requirement may not need to be 

met, but is recommended.

10.  Plan venting system to avoid possible contact with 

plumbing or electrical wires.  Start at vent connector 

on top of boiler and work towards vent terminal.

11.  If a non-standard length pipe is required:

  Gasketed Vent System: The use of the adjustable 

length pipe (P/N 8116319U) is recommended to 

complete a non-standard pipe length.  This pipe 

requires a minimum installed length of 12¾ inch 

and can adjust across a 7 inch gap up to a maximum 

of 19¾ inch long.  (Note for the adjustable pipe 

the installed length should be measured from the 

centerline of the bead on the male end of the first 

pipe to the end of the female pipe excluding the 

locking band of the second pipe with a single 

gasket.)  Only in the event the adjustable length pipe 

is not sufficient a standard length pipe may be cut 

using the procedure outlined below for the Gasket-

Less Vent System.

12. Vent connectors serving appliances vented by 

natural draft shall not be connected into any portion 

of mechanical draft systems operating under positive 

pressure.

WARNING

Never exceed maximum installed length of 19¾ 

inches for adjustable length pipe.

Risk of flue gas leakage is possible.

NOTICE

Cut  must  be  square  with  pipe  and  filed  or 

sanded smooth before joining.  Carefully ensure 

roundness of cut pipe by hand with gloves before 

installing.    Seal  joint  with  RTV  specified  in  this 

manual.

III.  VENTING (continued)

Maximum support spacing is five (5) feet (1.5 m).  

Do not penetrate any part of the vent system with 

fasteners.  

  Soutenez parties horizontales de ventilation pour 

éviter l’affaisement.  Utilisez des colliers de serrage, 

des crochets on cintres espacées de 5 preds (1.5 m) 

ou moins.

6.  Vent length restrictions are based on equivalent 

length of vent pipe (total length of straight pipe 

plus equivalent length of fittings).  Maximum 

vent lengths are listed in Table 4.  Do not exceed 

maximum vent lengths.  Table 3 lists equivalent 

lengths for fittings.  Do not include vent terminals in 

equivalent feet calculations.  

7.  Provide and maintain vent pipe minimum clearances 

to combustible materials.  Vent pipe minimum 

clearance to combustible material is four (4) inches 

(102 mm) when vent is installed in a fully enclosed 

(chase) application or three (3) inches (76 mm) 

when vent is installed with at least one side open, 

similar to a joist bay application.  Use double wall 

thimble [U.S. Boiler Part No. 103877-01 (3”), 

100185-01 (4”)] when penetrating a combustible 

wall.  

8.  Do not install venting system components on 

the exterior of the building except as specifically 

required by these instructions.  The vent termination 

location is restricted as follows:
a.  Bottom of vent terminal at least twelve (12) 

inches (300 mm) above grade plus normally 

expected snow accumulation level.

b.  Minimum three (3) feet (0.3 m) above any forced 

air inlet located within ten (10) feet (3 m).

c.  Minimum four (4) feet (1.2 m) below, four (4) 

feet (1.2 m) horizontally from, or 1 foot (300 

mm) above any door, operable window, or 

gravity air inlet into any building.

d.  Minimum clearance from electric meters, gas 

meters, regulators, and relief equipment.

  United States. Minimum 4 ft (1.22 m) 

horizontally from and in no case above or below, 

unless a 4 ft (1.22 m) horizontal distance is 

maintained.

  Canada. Minimum 6 ft (1.83 m) horizontally 

from and in no case above or below, unless a 6 ft 

(1.83 m) horizontal distance is maintained.

e.  Minimum twelve (12) inches from overhang or 

corner of building.

f.  Do not terminate over public walkways or over 

an area where condensate or vapor could create 

nuisance or hazard or could be detrimental to the 

operation of regulators, relief valves, or other 

equipment.