Danfoss AK-PC 551 User Manual page 24

The capacity from the digital scroll compressor
The capacity is divided into period times as "PWM period time". 100% capacity is delivered when cooling takes place for the whole pe-
riod. An off time is required by the bypass valve within the period and an on time is also permitted. There is "no cooling" when the valve
is on.
The controller itself calculates the capacity needed and will then vary it according to the cut-in time of the capacity control valve.
A limit is introduced if low capacity is needed so that the cooling does not go below 10%. This is because the compressor can cool itself.
This value can be increased if necessary.
Refrigeration
No refrigeration
Copeland Stream compressor
The pulse signal can also be used to control one stream compressor with one unloader valve *(4 cylinders version).
The compressor capacity is distributed by up to 50% for one relay and the remaining 50-100% for the unloader. The unloader is con-
nected to DO5 or DO6.
Bitzer CRII
The pulse signal can also be used to control one of the CRII with 2 unloaders (4 cylinders version).
Compressor capacity can be controlled from 10 to 100% depending on the pulsation of the unloaders.The unloader is connected to DO5
or DO6..
Unloader 2 follows unloader 1
but is offset a ½ period.
Sd monitoring
When regulating with Sd monitoring, one of the three compressor types will increase capacity if the temperature nears the Sd limit. This
will result in better cooling of the unloaded compressor.
Injection off
The electronic expansion valves in the cooling appliances must be closed when all the compressors are prevented from starting.
As a result, the evaporators will not be filled with fluid that can be led to a compressor when the regulation process restarts.
One of the compressor control relays can be used for this function, or the function can be prompted via data communication.
24
Period time
Min. Capacity
User Guide RS8GY302 © Danfoss 2015-06
Only DO5 or DO6
Unloader 1
Unloader 2
AK-PC 551