IBC V-10, Manual, Page: 30 / 103

target supply temperature range. The loads will be uncombined if the under
temperature condition persists after the Off Delay time. If the supply
temperature exceeds the requirements for either the Primary or Secondary
loads, the loads will no longer be combined.
Retry Delay If the boiler removes the Secondary load from combined service because
load combining conditions are not followed, the Retry Delay is the number
of minutes the boiler waits before attempting to add the Secondary load
back into combination service.
Maximum
Throttle % Maximum (percentage) of the boiler’s heat output below which load
combining is allowed to begin. If set at Maximum Throttle 75% for
example, the throttle needs to be operating at below 75% of the boiler's
heat output before the Secondary load is added into combined service. The
Maximum Throttle % has no effect once the loads have been combined.
Table 3 Default parameter settings in full mode load combining
Example of compatible load combining
Primary Load 140 °F to 180 °F
Secondary Load 150 °F to 170 °F
Initial Delay: 5 mins
Off Delay: 5 mins
Retry Delay: 10 mins
Maximum Throttle %: 75 %
The boiler will wait a minimum of 5 minutes (initial delay) after it begins servicing the
Primary load before adding the Secondary load.
The supply temperature must be between 150 °F and 170 °F (the compatible
temperature range for both loads), and the throttle is below 75%, before the secondary
load is added.
If the supply temperature rises above 170 °F, the load is dropped.
If the supply temperature is/or drops below 150 °F after the 5-minute "Off Delay", the
secondary load is also dropped.
If the secondary load is dropped, the boiler waits a minimum of 10 minutes (Retry
Delay) before attempting to add the Secondary load again. At this time, the supply
temperature must be between 150 °F and 170 °F.
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Section: Operating concepts