How do I make this safer than it is now?

[yellowvanman]

TT system wired about 10 years ago, using a 16th Edition board but with no 100mA RCD as main switch. (muppet!)

As it stands the 30mA doesn't trip and so needs changing anyway.

Whats the best way to protect the non RCD circuits without spending a fortune? The options I think I have are:

1) Change main 100A switch for a 100mA time delayed RCD - as it should have been in the 1st place

2) Change main 100A switch with a 30mA RCD - trouble is there is no discrimination with the other RCD in the board! Or don't even bother changing the other RCD and just have 1 protecting all circuits!

3) Change non RCD MCBs with RCBOs - too expensive.

Anyone got another option? I'm inclined to do No. 2.

 

[yellowvanman]

If this is your typical 200 ohm UK TT system, then it's got to be all RCBO, with a 100mA RCD front end!! .... As wirepuller says it'll not be too often, you'll get two RCD devices failing on you at the same time... lol!!

Ze isn't that bad 13 ohms ish. Ideal situation would be to put RCD and RCBOs but in the real world some people can't afford it!

 

[durhamspark]

I had 1 similar to this recently although it was a tncs system.

The problem I had was that I had carried out alterations to a few of the circuits on the main switch side of a 16th ed split load board meaning I had to rcd protect them as the cables were buried in the plaster.

It was a tight board so rcbos simply would not fit. The way I saw it I had 2 options.

1. move mcbs across to rcd side and buy new busbar comb as the existing did not have enough spares

2. Replace main switch with 30mA rcd and as the links were flexible, feed the 2nd rcd from the supply side of the main one so they are not connected in series.
I was fortunate in this case as there was an isolator switch in the meter cabinet so I removed the "Main Switch - isolates all circuits " sticker and made a warning label stating "isolate at meter cabinet"

This may be an option for you to consider.

 

[Engineer54]

Ze isn't that bad 13 ohms ish. Ideal situation would be to put RCD and RCBOs but in the real world some people can't afford it!

That's Good to hear. Well there's certainly one thing you can do to improve this installation then, with an already existing Ra of 13 ohms.... lol!!!

 

[telectrix]

bang in a scaffold pole?

 

[Engineer54]

bang in a scaffold pole?

Haha!! ...Seen that done before too, as well as other bits of discarded pipework!!

 

[yellowvanman]

2. Replace main switch with 30mA rcd and as the links were flexible, feed the 2nd rcd from the supply side of the main one so they are not connected in series.
I was fortunate in this case as there was an isolator switch in the meter cabinet so I removed the "Main Switch - isolates all circuits " sticker and made a warning label stating "isolate at meter cabinet"

This may be an option for you to consider.

Yes I've seen that before but forgot all about it - thanks.