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XI. Wiring (continued)
CAUTION
When making low voltage connections, make sure that no external power source is present in the
thermostat or limit 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 the old thermostat wiring.
Do not attempt to use EnviraCOM connections for any purpose not explicitly permitted by the boiler
manufacturer. Attempting to do so may result in unreliable operation and/or damage to controls.
c) Low water cut-off wiring – Although not necessary to protect this boiler (see Part IX), some jurisdictions may insist that
a low water cut-off (LWCO) be installed with this boiler. There are two ways to wire a LWCO into this boiler:
• A 120V LWCO may be wired to break 120V power to the boiler (Figure 11.4a)
• A 24V LWCO may be wired so that its contacts are wired to the external limit connections on the boiler. When
this is done a separate transformer must be supplied by the installer to power the LWCO’s sensing circuit. This
transformer must be completely isolated from the boiler wiring (Fig 11.4b).
3) Data Connections – Modbus and EnviraCOM connections are located in the green control connector shared with the display
connections (Figure 11.5). These connections have the following uses:
a) EnviraCOM - Used to connect EnviraCOM thermostat or other EnviraCOM device listed by the boiler manufacturer
for use with this boiler.
b) MODBUS - Boiler-To-Boiler communication network is used for multiple boiler (“Lead-Lag”) installations. Note that
combi boilers may only be used as slaves in such a system.
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