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Discuss Using one phase of three phase supply, will rcd work properly? in the New Member Introductions area at ElectriciansForums.net

mikeytgw

New EF Member
I have a property abroad that has just been given a new supply by my local electrician . It has gone from six mm2 single phase supply to 10 mm2 three-phase supply

it has a three-phase RCD unit and currently is only using one of three phases
The other phases will come into use when the building is extended and the garage is built and has some machinery in it
My question is when I pressed the test button on the RCD it did not click the RCD off and I think that might just be a feature of the way it creates a test condition

but will the three-phase RCD detect any small currents over the 30 milliamperes limit and switch the supply of or does the system need to be fitted with a single phase RCD ??

Thanks for any replies
Mikey
 

snowhead

Respected Member
Forum Mentor
Trainee Access
Yes it will work on 1 phase , the test button circuit only uses 1 phase.
There will be a diagram on the RCD showing which phase the Test circuit uses.
If you think about it, if all phases were connected there could be a fault on just 1 phase and it would still trip.
 

Barnaby Stedman

Regular EF Member
You might want to think about nuisance tripping when the other two phases are being wired in. Because with the current set up it will trip your single phase too which may be a pain if your not in the house to realise.
 

Wilko

Electrician's Arms
Sounds like your local Electrician did not push the test button? It should be left so that you can use the button to test it. In this pic the test button connects the phase on terminal 2 to N via a resistor. If there is no phase in terminal 2 the test button won’t work.

4359F1EF-C022-4EB4-ABD3-79276995CA63.jpeg
 

mikeytgw

New EF Member
You might want to think about nuisance tripping when the other two phases are being wired in. Because with the current set up it will trip your single phase too which may be a pain if your not in the house to realise.
Thanks for all the replies
Very helpful
I will make sure when I am back that it is wired to the phase that the tester trips
 

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