Page 73 - HVAC Pump Handbook

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Piping System Friction
70 The Basic Tools

3. Hydraulic shock. Plastic pipe does not have the withstandability
of steel pipe. The actual configuration of the plastic pipe installa-
tion, including methods of support, should be approved by the
manufacturer of the plastic pipe.
4. Maximum allowable velocity. Table 3.2 outlines maximum veloci-
ties for steel pipe. These velocities are excessive for most types of
plastic pipe. Actual maximum velocities under consideration for a
specific installation of plastic pipe should be approved by the man-
ufacturer of the plastic pipe.
Most manufacturers of plastic pipe have very good application man-
uals that provide most of the answers to the preceding installation
variables.

3.5.1 Types of plastic pipe used in HVAC
Following is information on the some of the more common plastic pipe
used in HVAC water systems:

PVC. Polyvinyl chloride pipe: ASTM D-1784 Class 12454-B
CPVC. Chlorinated polyvinyl chloride pipe: ASTM D-1784 Class
23447-B
PVC pipe has been the preferred plastic pipe for HVAC water sys-
tems for many years. For installations operating at higher tempera-
tures, CPVC has provided an excellent material for piping. The
pressure-temperature relationships for these types of plastic pipe are
provided in Table 3.15.

TABLE 3.15 Maximum Operating
Pressure (psig) versus Temperature (°F)

Operating
temperature PVC CPVC
Up to 100 150 150
110 135 140
120 110 130
130 75 120
140 50 110
150 N.R. 100
160 N.R. 90
170 N.R. 80
180 N.R. 70
190 N.R. 60
200 N.R. 50

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