Crown Boiler TWB Series, Installation Instructions Manual

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CAUTION
• When making low voltage connections, make sure that no external power source is
present in the thermostat circuits. If such a power source is present, it could destroy the
boiler’s control. One example of an external power source that could be inadvertently
connected to the low voltage connections is a transformer in old thermostat wiring.
• Do not use the transformer provided on the boiler to power external devices such as
zone valves. Doing so may cause damage to the transformer.
2) Low Voltage Connections – Low voltage field connections are located as shown in Figure 11.0 and 11.1 and are as follows:
• T-T - Connect to a 24 volt heating thermostat or other “dry contacts” (such as a zone panel end switch) that close upon
a call for heat. Follow thermostat manufacturer’s instructions. To insure proper thermostat operation, avoid installation
in areas of poor air circulation, hot spots (near any heat source or in direct sunlight), cold spots (outside walls, walls
adjacent to unheated areas, locations subject to drafts). Provide Class II circuit between thermostat (or zone controls) and
boiler.
3)
Adding a Second Circulator Zone - The control provided on this boiler can be used to control a second heating or DHW
circulator zone. If this is done, make the following 120VAC connections in addition to those described above (also see Figure
11.0):
• Connect a 120VAC heating or DHW thermostat for the second zone between ZC and ZR.
• Connect the DHW circulator or the second heating zone circulator between ZR and L2.
See Part XIII of this manual for information on configuring the control to respond properly to the DHW or second heating
zone circulator.