
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
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
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 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.
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.)
*
*Maximum 4 times the pipe diameter or 12”, whichever is less.
Fig. 11: Single Heater - Low-Temperature (Heat Pump)
Application with Primary/Secondary Piping
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
*
*Maximum 4 times the pipe diameter or 12”, whichever is less.
Fig. 12: Dual Heaters (Reverse/Return)
with Primary/Secondary Piping
Domestic Hot Water
When designing the water piping system for domestic 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 ex- pressed in grains per gallon.
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