Raypak XTherm Series Installation & Operating Instructions Manual page 18

Fig. 18: MODE 1 - Boiler Cascade with Primary/
Secondary Piping
NOTE: In cascade configuration the system pump
and DHW pump (if applicable) outputs from each
cascade member must be connected in paral-
lel to activate the system pump and DHW pump
during "limp along" operation respectively. See Cat.
5000.72 VERSA manual for detailed information.
NOTE: MODE 1 can also be used for process heat-
ing applications in conjunction with a buffer/storage
tank when operating temperatures above 160°F are
required. Water hardness must be no more than 15
grains per gallon for scale-free operation.
Fig. 19: MODE 2 - Single Boiler with Indirect
on System Loop
Mode 2 (Type H Units Only)
This mode selection is for hydronic heating systems
with single or multiple boilers (Maximum 4 boilers)
in primary/secondary piping configuration with or
without Outdoor Air Reset (S4) with indirect DHW on
the system loop (with or without priority). The system
temperature is controlled by the System sensor (S3).
The Indirect DHW sensor (S5) determines the indirect
call/tank setpoint. The system temperature is boosted
to Target Max when using the Indirect DHW sensor
(S5) during an indirect call for heat. Priority mode
toggles off the System Pump (P2) when an indirect
call for heat is present. The Boiler/Injection Pump (P1)
runs during any call for heat. The Indirect DHW Pump
(P3) runs during an indirect call for heat with no "off"
delay. The Boiler/Injection Pump (P1) is delayed "off"
as user defined in the BOILER menu and the System
Pump (P2) is delayed "off" in the ADJUST menu.
The System Pump (P2) runs whenever the system is
enabled for heating and the outdoor air temperature is
lower than the WWSD temperature setting (if utilized)
unless an indirect call for heat is present with priority.
Fig. 20: MODE 3 - Single Boiler with Indirect
Mode 3 (Type H Units Only)
This mode selection is for hydronic heating systems
with single or multiple boilers (Maximum 4 boilers) in
primary/secondary piping configuration with or with-
out Outdoor Air Reset (S4) with indirect DHW on the
boiler loop (with priority). The system temperature
is controlled by the Supply sensor (S3) whenever
the indirect call for heat is not active. The DHW
Supply sensor (S5) determines the indirect call/tank
setpoint. During an indirect call for heat the boiler
firing rate is determined by the water temperature at
18
on Boiler Loop