RCBO for old Square D distribution board

[westward10]

Maximum Zs values for Type 4 devices have never been quoted in the Regulations so you have to refer to manufacturers figures. Type 4 devices unlike other circuit breakers used 0.4 and 5 sec disconnection times, so 0.4 for socket outlets and 5 sec for fixed equipment.

 

[Toneyz]

It may get to a point that if any further additions/work is carried out and requires RCD/RCBO protection a new consumer unit would be cheaper in the long run if the prices are too high eg a BG 5 +5 split £73 inc VAT.

 

[soms]

Replacement is another option, but it would a fair job, as there are also off-peak circuits so would require two new consumer units.

 

[Toneyz]

Well never knew that you kept that quiet.

 

[suffolkspark]

I cant see how ---- arsing around putting an rcd inline below the board is gonna work out cheaper than the £65.28 that a correct new rcbo is?

 

[soms]

I cant see how **** arsing around putting an rcd inline below the board is gonna work out cheaper than the £65.28 that a correct new rcbo is?

That is probably true. They won't grudge spending the money, I told them something should be done before any alterations are made.

I will just buy one.

Thank you all for helping me bat some ideas around and pointing me to a suitable retrofit item.

 

[soms]

I replaced the circuit breaker with the new RCBO last night.
I tested the circuit Riso, Zs, and the RCD trip times.

Riso live conductors to earth was under 1 Mohm so needs some further investigation, but not at 8.30 in the evening.
Zs 0.77 ohms.

The RCD trip times are not meeting the requirements for additional protection.

I repeated the test three times using a Fluke MFT, the meter was set for the correct characteristics - type AC, 30 mA.

x1 - 49.4 ms and 76.5 ms - less than 300 ms so acceptable.
x5 - 41.6 ms (180 deg.) and greater than 50 ms (0 deg.) - neither are acceptable readings for providing additional protection as over 40 ms.

A quick Internet search did not reveal what the operating times should be for the BS EN 61009-1 product standard (if any different to those quoted to meet the requirements in BS 7671).

I am considering contacting the supplier to ask about a replacement RCBO as I am not entirely happy with it, but I first I wanted to try and find out whether the product is working as it should or not, hence the question about the product standard requirements versus BS 7671.

 

[westward10]

Did you test it with the outgoing circuit disconnected.

 

[soms]

Did you test it with the outgoing circuit disconnected.

No, I didn't, I tested it at a socket outlet with the circuit connected.

I can see where you are going with this, would you repeat the tests at the RCBO terminals without the circuit connected?

 

[westward10]

Yes, it should trip within the prescribed times for an EN61009 device.