25
The system will operate the indirect DHW call with pri-
ority only. The cascade firing rate will be controlled by
the System Supply Sensor connected to the Master
boiler (S3a) whenever the indirect call-for-heat is not
active. See
System Sensor Installation
on page 9.
The Indirect DHW Sensor (S5a) determines the indi-
rect call/tank set-point. When using an indirect DHW
sensor to control tank temperature, contact closure is
required across the indirect override connections for
proper operation. To ensure proper operation during
"limp-along" mode, connect an aqua-stat across the
indirect DHW override terminals of master unit, install
a jumper across indirect DHW terminals of follower
units and set the rest of the follower PIM™'s operator
dial to be equal to DHW Target temperature. In lieu of
an aquastat across the indirect DHW override termi-
nals of the master unit, a jumper may be used. This
configuration requires all PIM™ operator dials be set
to DHW Target temperature to prevent an over-temp
condition from occurring during "limp-along". It is also
recommended the system pump and DHW pump be
connected in parallel from each cascade follower, to
allow these pumps to be functional during limp-along
operation. During an indirect call-for-heat, the firing
rate is determined by the Indirect Setpoint (or Max
Target) at the Indirect Supply Sensor (S6a). The sys-
tem will provide Max Delta T control to cycle the burner
if the Max Delta T is exceeded between Boiler Outlet
Sensors (S1a-b-c-d) and Boiler Inlet Sensors (S2a-b-
c-d).
In order to enable MIX settings, VERSA
®
DIP #3 must
be set to ON position. Raypak’s Cold Water protection
system utilizes a proportional 3-way valve to bypass
water from the boiler outlets to the inlets (S2 a-b-c-d)
during operation, when the system return water tem-
perature is below the minimum acceptable level,
Item
Range
Default
User Settings
When is it
Displayed
Description
BOILER 1, 2, 3, 4
ON <> OFF
OFF
Cascade
Followers present
FT_Bus 1, 2, 3, 4 are connected
among all active units, as defined in the Installation
and Operating manual for the product being installed.
Priority mode toggles off the System Pump (P2a)
when an indirect call-for-heat is present. Boiler Pumps
(P1a-b-c-d) run in conjunction with their associated
burner during all heat calls regardless of priority. The
Indirect DHW Pump (P3a) runs during an indirect call-
for-heat with no “off” delay. The Boiler Pumps
(P1a-b-c-d) and System Pump (P2a) delay “off” as
user-defined in the ADJUST menu. The System Pump
(P2a) runs whenever the system is enabled for heat-
ing and the outdoor air temperature is lower than the
WWSD temperature setting (if utilized) unless an indi-
rect call for-heat is present with priority.
Mode 3 is used for this configuration. Ensure DIP
switches #1 and 2 on the VERSA
®
master Control
Board are in the ON position to make programming
changes. Prior to setting any DIP switches, the heater
must be turned off. It is important to remember to
enable a boiler to be a follower in the cascade by turn-
ing DIP switch #2 on the VERSA
®
Control Board to the
"OFF" position for each of the followers. To enable
Follower boilers, scroll to the SETUP menu at the
Master boiler and, using the item button, scroll to the
individual boilers and toggle from OFF to ON to allow
them to operate when commanded by the Master to
run.
Prior to setting any DIP switches, the heater must be
turned off. Prior to enabling the master boiler apply
power to all units for initial programming of cascade
settings. This is accomplished from the master boiler
user interface.
The next menu items are not necessarily in the order
in which they will appear.
Enable followers from appropriate BOILER menu at the master:
Summary of Contents for 5000.72A
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