Marcus asks this question about the correct use of AC distribution equipment for a 110V DC application, and it includes whether isolator de-rating is required, as well as energy let-through issues. It has been answered by Schneider Electric (Theme – Distribution Equipment):
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Question: I’m looking to use an Isobar 4 Type B distribution board for a 110V DC application and have a standard four-pole MGI1254 isolator and C60HB402 and C60HC406 MCBs fitted, along with a single-phasing kit and distributed neutral.
Note that I’m using the bigger IP55 board as I want to use the distribution board for a future application.
The isolator has a utilisation category of AC23 and the MCBs require double pole isolation on the positive and negative legs.
I have two questions:
1) As the magnetic overating figure is 1.38, do I need to apply this to the let-through energy of the device (i.e. make sure the cable can take the short term let through)?
2) Do I have to de-rate the isolator for the DC23 utilisation?
Answer: The magnetic will not apply to the let through, but you still have to have the cables rated to the let-through.
Having an AC23 switch-disconnector, you will have to make sure it is capable of breaking a DC current.
Our standard MGI1254 is NOT DC23 rated. We have no certificates for these on a DC system, The C60Hs are OK and the distribution board is OK, but you may have to change the incomer. Our new Acti9 range has DC rated incomers.
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