15
Fig. 7: MODE 1 - Applications with Primary/Secondary Piping
Fig. 8: MODE 2 - Single Boiler with Indirect
on System Loop
Key:
S1: Boiler Outlet Sensor
S2: Boiler Inlet Sensor
S3: System Sensor
S4: Outdoor Air Sensor
S5: Indirect Tank Sensor
S6: Supply Sensor to Indirect
P1: Boiler Pump
P2: System Pump
P3: Indirect DHW Pump
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 sys-
tem 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 tog-
gles off the System Pump (P2) when an indirect call for
heat is present. The Boiler 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
Pump (P1) and System Pump (P2) delay “off” as user
defined 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.
NOTE:
MODE 1 can also be used for process heat-
ing applications in conjunction with a buffer/storage
tank when operating temperatures above 150
°
F are
required. Care must be given to ensuring water hard-
ness is less than 5 grains per gallon to ensure scale
free operation.
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 without
Outdoor Air Reset (S4) with indirect DHW on the boil-
er 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
Summary of Contents for 300A
Page 44: ...WIRING DIAGRAM 44...
