Will an rcd operate

[Jako13!]

Will an rcd operate on the secondary part of a transformer if the primary side is RCD protected?

Thanks in advance for your help

 

[stevethesparks]

All depends on what sort of transformer it is.
Isolating?
Auto (neutral carried through to secondary)?
Is the earth connected to the secondary center tap?

 

[Jako13!]

All depends on what sort of transformer it is.
Isolating?
Auto (neutral carried through to secondary)?
Is the earth connected to the secondary center tap?

If it’s 400v input 110v to earth output?

 

[pc1966]

If it’s 400v input 110v to earth output?

That is not answering the issue of isolation!

 

[Jako13!]

That is not answering the issue of isolation!

No it’s not an isolating transformer

 

[westward10]

If you have primary and secondary it is likely to be isolating. Sounds like a site transformer.

 

[James]

Can you draw a diagram of the arrangement and post it?
I am unsure if you are asking

A rcd feeding primary side, will a fault on secondary fed circuit trip it.

B if you have an rcd on the primary supply, will a second rcd on secondary output still work.

 

[pc1966]

As well as the issue of isolated or not, the question of the effectiveness of an RCD on the output of an isolated transformer is also dependent on how it is earthed (if at all).

Some transformers (e.g. shaver supply) result in an IT arrangement and an RCD is of little use, but a typical 110V site transformer is 55-0-55 with the centre earthed, and for that an RCD is going to work even though 55V to earth is usually considered safe enough not to need it.

Usually is not always!

 

[Jako13!]

Can you draw a diagram of the arrangement and post it?
I am unsure if you are asking

A rcd feeding primary side, will a fault on secondary fed circuit trip it.

B if you have an rcd on the primary supply, will a second rcd on secondary output still work.

Not the best diagram aha

 

[pc1966]

OK, so try answering a few questions first to see if you can deduce the answers:

1) Is the transformer you sketched isolating on not?
2) What path for current in a RCD trips it?
3) To answer question (a) is your answer to #2 normally present in this arrangement?
4) Your question (b) has several aspects:

• What is your definition of "not work"?
• How might two RCD in series fail to meet the IET regulation 536.4.1.4?
• Returning to your answer to #2, is that present in your diagram for the secondary circuit?

 

[Jako13!]

OK, so try answering a few questions first to see if you can deduce the answers:

1) Is the transformer you sketched isolating on not?
2) What path for current in a RCD trips it?
3) To answer question (a) is your answer to #2 normally present in this arrangement?
4) Your question (b) has several aspects:

• What is your definition of "not work"?
• How might two RCD in series fail to meet the IET regulation 536.4.1.4?
• Returning to your answer to #2, is that present in your diagram for the secondary circuit?

OK, so try answering a few questions first to see if you can deduce the answers:

1) Is the transformer you sketched isolating on not?
2) What path for current in a RCD trips it?
3) To answer question (a) is your answer to #2 normally present in this arrangement?
4) Your question (b) has several aspects:

• What is your definition of "not work"?
• How might two RCD in series fail to meet the IET regulation 536.4.1.4?
• Returning to your answer to #2, is that present in your diagram for the secondary circuit?

My understanding is it wouldn’t work as it has a separate live and neutral. So to rcd protect it we’d have to put an rcd downstream and change the upstream to a time delay to comply with regs