Special Control - Sinclair SCV-750EB Service Manual

7 Special Control

7.1 Outdoor Unit Duty Cycling
In systems with multiple outdoor units, outdoor unit duty cycling is used to balance the compressor running time. Outdoor unit
duty cycling occurs whenever all the outdoor units stop running (either because the leaving water set temperature has been
reached or because a master unit error has occurred):
Take 16 units in parallel as an example:

First cycle:
When the outdoor units are powered on for the first time, if there is a load requirement, 50% of the units turn on starting
with the 0# master unit to higher address slave units. As the leaving water temperature approaches its set temperature, units
shut down in succession, starting with the unit with the highest address.
Startup
Loading
Offloading
 Second cycle:
The next time a load requirement exists (or following a master unit error), the units turn on starting with the highest
address unit to lower address units. As the leaving water temperature approaches its set temperature, units shut down in
succession, starting with the unit with the lowest address.
Startup
Running
Loading
Offloading
 Subsequent cycles will repeat the actions of the first and second cycles
Notes:
1. The address settings on the outdoor unit main PCBs for master unit and slave unit do not change.
Startup Startup
1 2
Running Running
1 2
Offloading in sequence (from 16 to 1)
1 2
Startup Startup
16 15
Running
16 15
Offloading in sequence (from 1 to 16)
16 15
Startup
¡ -
8
Loading in sequence (from 9 to 16)
Running
¡ -
8
¡ -
8
Startup
¡ -
9
Loading in sequence (from 8 to 1)
Running
¡ -
9
¡ -
9
¡ -
9 16
¡ -
9 16
¡ -
9 16
¡ -
8 1
¡ -
8 1
¡ -
8 1
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