Rheem Raypa DELTA 399B Installation And Operation Manual page 17

Pressure Drop in Feet of Head
Feedwater Regulator
Raypak recommends that a feedwater regulator be in-
stalled and set at 12 psi minimum pressure at the high-
est point of the system. Install a check valve or back
flow device upstream of the regulator, with a manual
shut-off valve as required by local codes.
Piping
All high points should be vented. Purge valves and a
bypass valve should be installed. A heater installed
above radiation level must be provided with a low wa-
ter cut-off device (sales order option F-10). The heater,
when used in connection with a refrigeration system,
must be installed so that the chilled medium is piped
in parallel with the heater with appropriate valves to
prevent the chilled medium from entering the heater.
The piping system of a hot water heater connected to
heating coils located in air handling units where they
may be exposed to circulating refrigerated air, must be
equipped with flow control valves or other automatic
means to prevent gravity circulation of the heater water
during the cooling cycle. It is highly recommended that
the piping be insulated.
Air-Separation/Expansion Tank
All heaters should be equipped with a properly sized
expansion tank and air separator fitting as shown in
Fig. 10.
Fig. 10: Air-Separation/Expansion Tank
Three-Way Valves
Valves designed to blend water temperatures or re-
duce water circulation through the heater should not
be used. Raypak heaters are high-recovery, low-mass
heaters which are not subject to thermal shock. Ray-
pak offers a full line of electronic sequencers that pro-
duce direct reset of heater water temperature. (Refer
to the Controls section of the Raypak Catalog.)
Fig. 11: Single Heater - Low-Temperature (Heat Pump)
Application with Primary/Secondary Piping
Fig. 12: Dual Heaters (Reverse/Return)
with Primary/Secondary Piping
Domestic Hot Water
When designing the water piping system for domes-
tic hot water applications, water hardness should be
considered. Table H indicates the suggested flow rates
for soft, medium and hard water. Water hardness is
expressed in grains per gallon.
SYSTEM SENSOR
5' MAX
5' MAX
12" MAX
SYSTEM SENSOR OR MIN FEASIBLE
(4:1 TURNDOWN
OR GREATER)
(LESS THAN
4:1 TURNDOWN)
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