Raypak MVB 504A, Installation & Operating Manual

Page: 27 / 64

27
NOTE: This dry contacts closure can come from a
room thermostat or a remote relay. No power of any
kind should be applied to either of these terminals.
5. Connect the Enable/Disable wiring to terminals 11
and 12 on the field wiring strip located on the
Master boiler (See Fig. 25). This connection must
be provided through dry contacts closure.
Cascade Follower Pump
and Sensor Wiring
1. Once the primary boiler has been identified, addi-
tional boilers will be designated as follower boilers.
Ensure dip switch 2 on each follower VERSA is set
to the OFF/Down position.
2. For each follower boiler, connect the boiler pump
wires to the pump contactor at the rear of each
unit.
3. The System and DHW pump outputs are not used
in the Cascade Follower configuration.
Fig. 29: VERSA Follower
Modbus BMS Communication
The VERSA IC control is equipped as standard with a
communications port for connectivity to building
automation via Modbus protocol. Refer to the VERSA
IC manual (5000.72) for further information.
Alarm Connection
An alarm annunciator or light may be connected to the
alarm contacts on the field wiring terminals. The Alarm
Contacts are 3A rated dry contacts on a normally-open
relay that close during fault or lockout conditions, and
the maximum voltage across the contacts is 30 VAC or
30 VDC. See the Field Wiring as shown in Fig. 25.
In a cascade system, the alarm output of the master
boiler will be active if either the master boiler or follow-
er(s) have a lockout condition. The alarm output of the
follower boilers will only energize if a lockout condition
occurs on that specific boiler.
Venting
General
Appliance Categories
Heaters are divided into four categories based on the
pressure produced in the exhaust and the likelihood of
condensate production in the vent.
Category I – A heater which operates with a non-pos-
itive vent static pressure and with a vent gas
temperature that avoids excessive condensate pro-
duction in the vent.
Category II – A heater which operates with a non-pos-
itive vent static pressure and with a vent gas
temperature that may cause excessive condensate
production in the vent.
Category III – A heater which operates with a positive
vent pressure and with a vent gas temperature that
avoids excessive condensate production in the vent.
Category IV – A heater which operates with a positive
vent pressure and with a vent gas temperature that
may cause excessive condensate production in the
vent.
See Table K for appliance category requirements.
CAUTION: Proper installation of flue venting is
critical for the safe and efficient operation of the
heater.