Raypak Xfiire 300B Installation And Operation Manual page 26

signal to the VERSA. This allows the VERSA to optimize
the Indirect DHW demand to maintain the Indirect DHW
setpoint. The Indirect DHW thermostat switch closure is
still required when using the Indirect DHW Sensor. If a
VERSA is not present the PIM shall activate the Indirect
DHW pump whenever the Indirect DHW call is active. The
Heater pump will also be activated based on the Indirect
DHW piping configuration setting.
A CAUTION: Sensor and control wiring must NOT be
run in chases with line voltage.
A CAUTION: To prevent an over temperature condition
from occurring in the indirect DHW system during "limp-
along" operation, set PIM operator dial to be equal to
DHW Target temperature. See VERSA IC Manual (5000.72)
for more information on "limp-along" operation.
Wiring the Cascade System -
Communication Bus
1. Designate the primary heater as the master heater/
heater1 by leaving DIP switch 2 on the VERSA in
the ON position. All other VERSA controls require
DIP switch 2 to be toggled OFF, designating them
as followers. Follower VERSA boards are ignored
by their corresponding PIM modules. Use standard
18 AWG wire to connect the master VERSA to the
PIM on the followers. A total of 3 followers can be
connected to the VERSA on the master. For systems
requiring more than 4 connected heaters, an external
sequencer such as the Raypak Temp-Tracker Mod+
Hybrid can be used. See Figure 29.
2. It is recommended that the shortest length cascade
wiring possible be used to reach between the
heaters. Do not run unprotected cascade wiring
across the floor or where they will become wet or
damaged. Do not run cascade wiring parallel with, or
close to or against, high voltage (120 volt or greater)
wiring. Raypak recommends that the total maximum
length of each set of cascade wiring not exceed
200' (61 m).
3. Connect the cascade wires to the PIM-J3 terminals by
pressing down on the slots with a small screwdriver
and then inserting the wires into the holes. See Figure
28. Fault will occur if wires are reversed.
NOTE: If communications between the VERSA board
and PIM are lost for any reason, the PIM is fully capable
of stand-alone operation. This may be referred to as
"limp-along" operation in other areas of this manual.
The operator Set Point potentiometer (See Figure 29 -
located adjacent the PIM dip switches) is used to control
the operating set point in a "limp-along" operation. This
is the target outlet temperature used in the firing rate
calculations.
The maximum target set point is limited to the high limit
26
setting minus the operator safeguard, regardless of the
potentiometer position.
The PIM calculates the required firing rate demand using
PID -based algorithm, This algorithm uses the heater inlet,
outlet sensor values, AND the target set point from the
Operator Set Point potentiometer setting.
To prepare for possible "limp-along" operation, set the
Operator Set Point potentiometer on each heater PIM to
the desired target setpoint.
Figure 28. Cascade Wire Connection
VERSA
MASTER
F10159
PIM FOLLOWER 2, 3 OR 4
B A
J4
J3 J2
J5
J6
Figure 29. XFiire Cascade System Wiring
TO PIM MASTER
A
B
A
B
A
B
J1
R91
ON
SW2
OPERATOR
1 2 3 4 5 6 7 8 SET POINT