what would you do?

Superspark23 · Dec 3, 2011

Just tested an type s 100ma RCD, My tester doen't have an option to test time delay rcd's but it tripped out at 8ms on the 100ma setting on my tester, i believe that type of rcd should trip between 130-500 ms. Correct me if im wrong.

So should i replace the RCD With another type s 100ma rcd, or replace it with just a main switch?

The supply is TT Ze of 10.5 ohms 2 earth stakes one i cant get access to the other i can in good condition fairly new. All circuits are proteted by 30ma rcd's from an daul rcd board, theres 2 unprotected ways in the board, would you think its wise to put another type s 100ma rcd in just incase one of the others fail? Or am i just being over cautious?

SPARTYKUS · Dec 3, 2011

Hi Superspark23

...I'd borrow a tester that can test the RCD correctly, you don't appear to have any valid test results at present if your meter is not set up to test a time delay RCD !

What meter is it?

morph · Dec 3, 2011

normal rcd tester should be ok really, sounds like the rcd is faulty, there should not be two unprotected ways if compliant with 17th as its TT ( unless the circuits are more than 32 A.

Superspark23 · Dec 3, 2011

2 spare unprotected ways basicly if any one ever wants to put 2 rcbo's in maybe for an garage supply ect... That was my bad wording Every circuit is protected by an 30ma RCS

And the tester's an Robin kmp 5404dl, I borrowed it from work

morph · Dec 3, 2011

Superspark23 said:
2 spare unprotected ways basicly if any one ever wants to put 2 rcbo's in maybe for an garage supply ect... That was my bad wording Every circuit is protected by an 30ma RCS

And the tester's an Robin kmp 5404dl, I borrowed it from work

oh spare , ok i did not realise that they were spare

SPARTYKUS · Dec 3, 2011

Not trying to be retentive, AND don't know enough about how, say, my MFT tests an S type on the right setting as opposed to a non S type, but it might not be reading right. Not sure but my gut feeling is test it with the right tester first. Never heard of an S type suddenly becoming zippy fast....?
Just saying maybe test the tinker first before splashing out on a new 'un.

Where you based? If you're near I'd do it for you

Superspark23 · Dec 3, 2011

I might see if i can get hold of another tester from someone else, It's the 1st time ive used this rcd tester so its possible it could be faulty it was only calibrated 2 months ago though. I have seen that this rcd will trip before the 30ma ones sometimes infact its done that twice once when a toaster went and secondly when a flex to a lawn mower was cut through.

its an old wylex bs4293

the 2 30ma rcd's tested at at 1X's 27 and the other 35, and at 5X's 8 and 7 i linked out the main rcd to get a true readings on these.

And i'm from Norfolk

MarkieSparkie · Dec 4, 2011

BS 4293 RCDs are the general purpose, stand alone, types that were quite common years ago, but were phased out in the early 1990s. Most commonly found as a front end RCD of TT installation.
When testing a BS 4293 type RCD the testing method is the same as normal. @1/2xIΔn on both + and - phases, the RCD should not trip within 2s. @1xIΔn on both + and - phases the RCD must operate within 200mS (Note this is shorter than the BS EN 61008 RCDs we are familiar with). On 30mA RCDs only, test additionally @5xIΔn on both + and - phases, the RCD should trip within 40ms.
If it's a BS4293 S type (time-delay) RCD the testing method is a little different, first you may need to select the RCD time-delay test mode if your tester has one, and perform @1/2xIΔn on both + and - phases, the RCD should not trip within 2s, as normal. @1xIΔn on both + and - phases, there is a 200ms time-delay and 200ms fault time, the RCD should trip within 50% of the time-delay + 200ms and 100% of the time delay +200ms i.e. between 300-400ms@1xIΔn. Most testers don't allow testing at 5xIΔn in this mode, so it is inhibited automatically, the result is not required anyway even if the test is performed.
BS 4293 RCDs have since been replaced by the BS EN 61008 types.
The old Wylex BS 4293 types were notoriously failure prone. Usually by becoming more sensitive than normal or not being resettable. It used to be a regular little earner replacing those things.