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MCB Change on Socket Circuit - No RCD

Bees2699

Hello All,

I have a question which I'm sure will have lots of opinions, so look forward to hearing them. 

After having carried out an EICR some welding sockets have failed, some due to the size of the MCB in relation to the cables current carrying capacity and some due to Zs. The loading is not an issue so we are looking to downgrade the size of the breakers which will sort out both issues. However as these are feeding sockets if we change the MCB will these have to become RCD protected. Although they have a specific intended use I cannot guarantee they wouldn't be used for anything else. However due to cost implications the customer is not willing to pay for either 3 phase RCBO's or individual RCD's mounted by the board or for replacing the sockets to include RCD's. By the changing the MCB we would only be making the circuit safer and up to the standard when it was installed, however I would usually try and bring any circuit I work on up to current standards. But as there are about 8 three phase circuits affected its not a simple or cheap option to replace them all. 

Look forward to any opinions or articles relating to this matter.

Thank you 

Bees 

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  • 0

    some welding sockets have failed, some due to the size of the MCB in relation to the cables current carrying capacity and some due to Zs. The loading is not an issue so we are looking to downgrade the size of the breakers which will sort out both issues.

    You've probably already ahead of me on this, but just in case... some welding gear can have quite significant inrush/switch-on surge currents - so sizing MCBs just on nominal loading and/or reducing the type of MCB might risk nuisence tripping,

       - Andy.

  • 0 in reply to AJJewsbury

    Yes I believe that's why they were changed for a higher rating at some point, the current over rated breakers are not what was initially installed according to the customer, we have now failed them but they no longer have the larger welders and have said they are happy for them to be downgraded again. It is a machining workshop so they will only be used for certain purposes, but I also don't want it to come back and bite me

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  • 0 in reply to AJJewsbury

    Yes I believe that's why they were changed for a higher rating at some point, the current over rated breakers are not what was initially installed according to the customer, we have now failed them but they no longer have the larger welders and have said they are happy for them to be downgraded again. It is a machining workshop so they will only be used for certain purposes, but I also don't want it to come back and bite me

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