17
Fig. 13: WH Direct DHW - Single Heater with CWP (VS
Pump - MIX TYPE = 2)
Fig. 12: Low Temp Process - Open Loop: H model, Cascade with Storage Tank
Cold Water Protection: WH models
Direct DHW heating systems utilize a variable speed
pump arrangement (MIX TYPE = PUMP) to keep the
heater inlet at or above 105°F (41°C). The integrated
VERSA IC control system provides functionality to
control a single variable speed injection pump via an
added inverter drive to provide Cold Water Protection
to the system.
See Fig. 13 as an example of a single heater applica-
tion. For more information regarding this function see
VERSA IC manual, catalog 5000.72.
Hydronic Heating
System Design
Hot water heating systems all have unique levels of
operating diversity. Raypak equipment design utilizes
as little water mass as possible to ensure maximum
operating efficiency. Primary / Secondary piping
arrangement is the method recommended and the
only method supported by Raypak for installation of Hi
Delta equipment. Proper system design should
always include system flow in excess of the connected
boiler flow for proper operation (Boiler Flow + 15% =
Min. System Flow). When appropriate, a Buffer/De-
coupler Tank can be used where system flow may be
reduced below the connected boiler flow. Failure to
design for adequate system flow (i.e. bypasses, 3-way
control valves, flow limiting balance devices, buffer
tanks, etc.) will result in boiler short-cycling and poor
system performance. Always contact your local
Raypak representative for system design assistance
to avoid these issues.
Pump Selection
In order to ensure proper performance of your heater
system, you must install a correctly sized pump. Ray-
pak recommends using a 20°F ∆T as design ∆T. (∆T is
the temperature difference between the inlet and outlet
water when the heater is firing at full rate). If a ∆T of
larger than 20°F is necessary, see Table G for flow rate
requirements.
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