RCD on t/e submain?

[Paulf321]

Hi just found this site

I am in the process of testing some sudent flats, the flats are all supplied by 16mm t/e submains with seperate 16mm main earth conductors.

We are going to recommend split RCD boards in all the flats to comply with the 17th (no RCD protection on the existing boards), do the submains have to be RCD protected (t/e installed in ceiling/wall voids.)

If so how do you discriminate between RCDs?

I have just passed my 17th course but not sure on this one!

 

[seajayess]

You will defiantly require RCD protection unless you can change T/E with SWA or a cable with an Earthed outer sheath. Why not fit RCBO's at the supply end, I know you should have dual RCD boards 17th. Edition but how far do you go, rip the whole place apart to do it ! You could find out if you could use time delayed RCD's at the supply this would allow you to fit dual RCD boards hope this helps CJS

 

[Andy™]

unless the submain meets all the criteria for not needing and RCD, then you will need one. unless you can use SWA or pyro etc instead

unfortunately, if you do need an RCD on the submain, and there is an RCD is other end, there is no way to discriminate. either or both will trip if a fault on final circuit

 

[SPECIAL LOCATION]

Or re-route T&E's in surface trunking,

i.e. cables not buried <50mm, so RCD protection not required.

may look naff if a private home, but student flat probably less of an issue.



******DONT FORGET******

RCD protection is for buried in walls..

NOT ceiling or floor voids!

 

[SPECIAL LOCATION]

Hi just found this site I am in the process of testing some sudent flats, the flats are all supplied by 16mm t/e submains with seperate 16mm main earth conductors.

We are going to recommend split RCD boards in all the flats to comply with the 17th (no RCD protection on the existing boards), do the submains have to be RCD protected (t/e installed in ceiling/wall voids.)

If so how do you discriminate between RCDs?

I have just passed my 17th course but not sure on this one!

Sorry Paulf321..... :_|

also forgot to say....

welcome to the forum!! Applaud SmileyApplaud Smiley

grab a beer!Guiness DrinkGuiness DrinkGuiness DrinkBlushing

 

[jl-heating]

sub mains still confuse me, last 1`s i came across were on 10mm twin but using the 4mm earth.. i condemned it but was told it was fine.

was told it was ok to use fault protection on the water and gas main bonds with the correct value achieved.

9 kw shower on the circuit to.. crazy.....

 

[Riggy]

On with a job at the moment, two submains to remote CU's, customer can't understand why I want to run SWA within a stud wall - I wonder myself!

 

[Andy™]

On with a job at the moment, two submains to remote CU's, customer can't understand why I want to run SWA within a stud wall - I wonder myself!

'cant you just use that cheap lighting cable?!'

 

[Riggy]

'cant you just use that cheap lighting cable?!'

Wireski?

 

[batty]

Unfortunately this is what we have got to get over. Can the large tw/e not be put in earthed metal conduit. On rewires I have started to go back to putting cooker circuits in earthed metal conduit as I am totally against putting cooker circuits through RCD's. You are going to find a lot of instals with this problem.

Batty

 

[Andy™]

but in the case of a cooker trippin the RCD.... its usually a faulty cooker with a high earth leakage

 

[batty]

but in the case of a cooker trippin the RCD.... its usually a faulty cooker with a high earth leakage

The last one I had the element tested at 200meg but it was enough to trip

17th edition board second Rcd. Changed it has not tripped since. 200meg hardly faulty. When I did my training we where told not to put cookers/ immersion heaters through Rcd's. You obviously where trained different to me.

Batty

 

[Andy™]

have to admit for some cooker i have bypassed the RCD for 15 mins... most problems are dampness in elements. mostly if water has been spilt when its cold or been left unused for a long time (holiday etc). easily fixed by turning it on without RCD for a bit

 

[SLIPSHOD & SLAPDASH]

You dont have to do anything. You just list that the wiring conforms to an earlier version of BS7671 & code 4. Only if sockets that may be reasonably expected to supply equipment outdoors have no Rcd protection a higher code need be listed.

 

[batty]

I would agree with slips on this. Students should not be fixing stuff to walls etc anyway. I would assume 16mm would come down by consumer unit so unlikely to get damaged.

Batty