Strebel S-CB Px 120, Installation Operating & Maintenance Manual

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S-CB Px 120 Manual 25
7.2. Pumps: electrical power limits
General
- The inrush current of a conventional pump is approximately 2 ½ x its nominal current.
- The maximum current, that the relay on the PCB can switch, is 5 A.
The conclusion from this is that nominal currents of pumps, which are controlled by the PCB, may not exceed 2 A.
Pump P1 - boiler pump.
Modulating boiler pump is connected to fixed power supply 30-31-32. Relay P1 is not used.
Pump P2 - calorifier pump.
Pump P2 is a DHWi pump and is used when P4AA = 1, meaning the appliance is an indirect calorifier.
Pumps P1 and P2 are connected to one fuse of 5 A, so the total nominal current of pump P1 and P2 may not
exceed this 5 A. To limit the inrush current, switching sequence has been set, so that pump P2 always switches
100 ms later than pump P1.
The maximum nominal current of pump P2 must also be 2 A, again due to inrush current. P
max
= 460 W.
3 way valve.
The combined nominal current of pump P1 and the 3 way valve must be smaller than 5 A.
So, the inrush current of the 3 way valve must be lower than 3 A.
Pump P3 - system pump.
The nominal current of pump P3 must be equal to or lower than 2 A, implying P
max
= 460 W.
Warning (EC pumps):
In case of using an electronic commutating pump, the relays 1, 2 or 3 may not be used for the power connection,
because of the inrush current of the electronics of the pump.
Directly connect the pump to an external power supply.
Control connections of an EC pump can be established in several ways, set by parameter P5BN.
See § 11.1.7 on page 71.