Raypak MVB 504A Installation & Operating Manual

Raypak MVB 504A Installation & Operating Manual Manual pdf 27 page image

27NOTE: This dry contacts closure can come from aroom thermostat or a remote relay. No power of anykind should be applied to either of these terminals.5. Connect the Enable/Disable wiring to terminals 11and 12 on the field wiring strip located on theMaster boiler (See Fig. 25). This connection mustbe provided through dry contacts closure.Cascade Follower Pumpand Sensor Wiring1. 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 setto the OFF/Down position.2. For each follower boiler, connect the boiler pumpwires to the pump contactor at the rear of eachunit.3. The System and DHW pump outputs are not usedin the Cascade Follower configuration.Fig. 29: VERSA FollowerModbus BMS CommunicationThe VERSA IC control is equipped as standard with acommunications port for connectivity to buildingautomation via Modbus protocol. Refer to the VERSAIC manual (5000.72) for further information.Alarm ConnectionAn alarm annunciator or light may be connected to thealarm contacts on the field wiring terminals. The AlarmContacts are 3A rated dry contacts on a normally-openrelay that close during fault or lockout conditions, andthe maximum voltage across the contacts is 30 VAC or30 VDC. See the Field Wiring as shown in Fig. 25.In a cascade system, the alarm output of the masterboiler will be active if either the master boiler or follow-er(s) have a lockout condition. The alarm output of thefollower boilers will only energize if a lockout conditionoccurs on that specific boiler.VentingGeneralAppliance CategoriesHeaters are divided into four categories based on thepressure produced in the exhaust and the likelihood ofcondensate production in the vent.Category I – A heater which operates with a non-pos-itive vent static pressure and with a vent gastemperature 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 gastemperature that may cause excessive condensateproduction in the vent.Category III – A heater which operates with a positivevent pressure and with a vent gas temperature thatavoids excessive condensate production in the vent.Category IV – A heater which operates with a positivevent pressure and with a vent gas temperature thatmay cause excessive condensate production in thevent.See Table K for appliance category requirements.CAUTION: Proper installation of flue venting iscritical for the safe and efficient operation of theheater.