HeatStation™ CONDENSING WATER BOILER
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34-1161 05/17
10.15 Multiple Boiler Cascade System (INSTaller level access)
The Cascade function is intended to be used with any Multi Boiler installation. The EOS control system on
HeatStation is capable of controlling 12 boilers in a cascade system. Cascading multiple boilers is important for a
number of reasons.
NOTE:
When the boiler is referred to as condensing or non-condensing, remember that all HeatStation boilers are
condensing.
Cascading will match the building heat load by allowing the minimum number of boilers to operate in order to
meet the heat demand.
Cascading will attempt to balance the run time of each member of the boiler group. This is important long term
because it minimizes uneven wear on individual boiler and make it easier to estimate maintenance for the group.
Cascading can increase system efficiency by operating condensing boilers at the minimum firing rates longer.
Cascading can reduce component wear as well by operating fewer boilers at their maximum output.
1. Parallel Modulation Cascade can optimize system efficiency by operating condensing boilers at the minimum
firing rate and bringing additional boilers on when the enabled boilers reach the programmed burner modulation
rate. The
MOD COND %
is the parameter which selects that trigger modulation rate.The default value is 50%
and is adjustable up to 100%. Each boiler in this system must be identified as condensing. The
CONDENSE
parameter located in the
SOURSE
menu should be selected to be
ON
.
Example: In a 4 boiler system with the
MOD COM
parameter set at 75%, when the Master boiler reaches 75%
burner modulation rate, the EOS will enable boiler #2 and reduce the modulation rate to a minimum. As the heat
load increases, the EOS will increase the firing rate of both boilers in parallel until they both reach 75%. EOS
will then enable boiler #3 and so on.
2. Sequential Modulation Cascade will reduce component wear as well as electrical consumption by maximizing
the heat output of one boiler before bringing on additional boilers. When the
MOD COND
parameter is set to
100% the cascade function automatically becomes Sequential Modulation.
Example: In a 4 boiler system with the
MOD COND
parameter set at 100%, when the Master boiler reaches
100% burner modulation rate and the building load continues to rise, the EOS will enable boiler #2. As the load
continues to rise, EOS will modulate the boiler #2 burner to a higher firing rate until this boiler also operates at
100% and so on.
Fundamental to creating a cascade boiler system, is establishing the identity of individual boilers and the
communication between them. The
ADDRESS
parameter allows the user to assign a unique address for each
boiler. Because any cascade system requires that a common sensor be used regulate the operation of all boilers
in the system, the
P/S
(Primary/Secondary) hydronic system must be selected regardless of the type of piping
system utilized for the installation. See Section 10.7 for details.
Establishing the electrical connection between boilers requires a two wire cable. It is recommended that 18
gauge, stranded copper wire within a shielded cable. A twisted pair cable is not required but may be advisable
when communication wiring is run in a common conduit with high voltage, current carrying electrical service.