Rheem Raypak Delta Limited 399B Installation & Operating Instructions 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
highest 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 pre-vent 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 automat-
ic means to prevent gravity circulation of the heater
water during the cooling cycle. It is highly recommend-
ed 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
reduce water circulation through the heater should not
be used. Raypak heaters are high-recovery, low-mass
APPROVED
UNCONTROLLED DOCUMENT IF PRINTED
heaters which are not subject to thermal shock.
Raypak offers a full line of electronic sequencers that
produce 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
con-sidered. Table H indicates the suggested flow
rates for soft, medium and hard water. Water hardness
is expressed in grains per gallon.
17
SYSTEM SENSOR
4:1 TURNDOWN)
5' MAX
5' MAX
12" MAX
SYSTEM SENSOR OR MIN FEASIBLE
(4:1 TURNDOWN
OR GREATER)
(LESS THAN