Specifications

Logamax plus GB142 applications manual | 01.2012
Technical specifi cations are subject to change without prior notice
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GB142 Applications Manual
Appendix 3 - Adding DHW priority to a
multi-boiler cascade
Description
To add DHW priority to a multi-boiler cascade, use piping and
wiring as shown here.
Install a DHW tank aquastat in the indirect fired DHW tank.
Use a zone relay to turn the tank loading pump on and
communicate the heat demand to the cascade controller.
Closing contacts 7 and 8 on the MCM10 will fire one boiler after
the other until the heat demand is satisfied and the aquastat
shuts off, removing the heat demand signal from the MCM10
which shuts down all boilers.
NOTICE: For DHW priority, disable all other consumers during
a DHW heat demand by disconnecting their
circulators using the N/C contacts on the relay box.
NOTICE: This system may cause the boilers to ramp up to their
high limit. To prevent other zones from overheating,
take one of the following measures:
1. Disconnect circulators of consumers to be
protected from overheating using the N/C contacts
on the relay box.
2. Install high limits in the zones to be protected from
overheating.
3. Install thermostatic mixing valves in the zones to
be protected from overheating.