State GPH-90N - Manual (Page 28)

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FIGURE 28
A VENT USED IN A SPECIAL
VENTING SYSTEM WITH POSITIVE
VENT PRESSURE AND PASSING
T H R O U G H A R O O F S H A L L
EXTEND AT LEAST 450mm (18
in.) ABOVE THE HIGHEST POINT
WHERE IT PASSES THROUGH
THE ROOF SURFACE AND ANY
OTHER OBSTRUCTION WITHIN
A HORIZONTAL DISTANCE OF
450mm (18 in.). A VERTICAL
VENTING SYSTEM MUST BE
SUPPORTED EVERY 1.5m (5 ft.).
3 in. (7.6cm)
MIN. LENGTH
TERMINATION
MAY BE 45°
ELBOW OR A
“T” ELBOW
RODENT
SCREEN
(INSTALL
INTO
ELBOW)
ROOF
LINE
18 in.
(45cm)
FIGURE 29
IMPORTANT
The vent system must terminate so that proper clearances
are maintained as cited in local codes or the current
edition of the National Fuel Gas Code (ANSI Z223.1) and
as listed below:
1. Vent Termination must extend a minimum of 18
in. (46cm) above roof or 18 in. (46cm) above the
anticipated snow level to prevent blockage of the vent
termination, as shown in Figures 28 and 29.
VENT PIPE PREPARATION
1. INITIAL PREPARATION.
A. Make sure the solvent cement you are planning to
use is designed for the specifi c application you are
attempting.
B. Know the physical and chemical characteristics and
limitations of the PVC and CPVC piping materials
that you are about to use.
C. Know the reputation of your manufacturer and their
products.
D. Know your own qualifications or those of your
contractor. The solvent welding technique of joining
PVC and CPVC pipe is a specialized skill just as any
other pipe fi tting technique.
E. Closely supervise the installation and inspect the
fi nished job before start-up.
F. Contact the manufacturer, supplier, or competent
consulting agency if you have any questions about
the application or installation of PVC and CPVC
pipe.
G. Take the time and effort to do a professional job.
Shortcuts will only cause you problems and delays
in start-up. By far, the majority of failures in PVC and
CPVC systems are the result of shortcuts and/or
improper joining techniques.
2. SELECTION OF MATERIALS.
• Cutting Device - Saw or Pipe Cutter.
• Deburring Tool, Knife, File, or Beveling Machine (2
in. and above).
• Brush - Pure Bristle.
• Rag - Cotton (Not Synthetic).
• Primer and Cleaner.
• Solvent Cement - PVC for PVC Components and
CPVC for CPVC Components.
• Containers - Metal or Glass to hold Primer and
Cement. Select the type of PVC or CPVC materials
to be used on the basis of their application with
respect to chemical resistance, pressure rating,
temperature characteristics, etc.
• Insertion Tool - Helpful for larger diameter pipe and
fi ttings 6 in. (15cm) and above.