Time delay RCCB

[westie101]

nother 'outhouse CU' in the outhouse? If so, why - and what is the one in the house being fed from

John W2, stop, take a deep breath and read the whole thread again, all the answers are there and you are confusing us and the OP with your questions


The OP posted this at 10:20, I would suggest that the reason for a separate CU in the house is possibly because the existing one could be full

All three boards in the house . Lighting board, power board and outhouse board ( yes is a very big house) are protected by a 100amp 30ma mains switch.

 

[deadshort]

I assume 100a 30ma switch x 3 ? If x1 i would not like to fault find in that house!

Regards,

DS

 

[JohnW2]

nother 'outhouse CU' in the outhouse? If so, why - and what is the one in the house being fed from

John W2, stop, take a deep breath and read the whole thread again, all the answers are there and you are confusing us and the OP with your questions

Yes, I'd forget the previous reference to an outhouse CU in the house. Apologies However, all the answers are not there - in particular the answer to my second question which you have quoted above.

Kind Regards, John

 

[JohnW2]

I assume 100a 30ma switch x 3 ? If x1 i would not like to fault find in that house!

Indeed! I must say that I did take it to mean "x1", given...

All three boards in the house ... are protected by a 100amp 30ma mains switch.

...but that might just have been imprecise wording on the part of the OP.

Kind Regards, John

 

[Andypease1]

Sorry have confused everyone.

System will be as follows ( it is a big house)

Incoming mains to 100a 30ma main switch

3 sets of tails to 3 separate consumer units

Unit one 100a in house DP main switch contains mcb's for power circuits in house plus cooker

Unit two in house100a disconnector switch contains mcb's for lighting circuits, aerial and alarm. Also has RCBO feeding pond and RCBO. Feeding an electric shower.

Unit three in house (The new one) to feed outhouse/work shop 63amp RCCB. (Non time delay) 40a mcb to feed outhouse plus 3 spare slots
6mm SWA to outhouse

Unit four in outhouse fed from the 40a mcb via 6mm SWA. 100a disconnector with 2 16a mcb for power and 2 6a mcb for lighting.

Protection for the 63amp rccb in

Does all that stack up. Cost not important as have all the kit already.

Cheers

 

[JohnW2]

Sorry have confused everyone. System will be as follows ( it is a big house) ... Incoming mains to 100a 30ma main switch ... 3 sets of tails to 3 separate consumer units

OK. Thanks for clarifying. As I wrote to deadshort, that's what I suspected. Do I take it that this "100A 30mA main switch" is a non-time-delayed RCD/RCCB?

Unit one 100a in house DP main switch contains mcb's for power circuits in house plus cooker ... Unit two in house100a disconnector switch contains mcb's for lighting circuits, aerial and alarm. Also has RCBO feeding pond and RCBO. Feeding an electric shower.

OK. Are those "DP mains switch" and "100A disconnector switch" the same things, and just switches, rather tha RCDs/RCCBs?

Unit three in house (The new one) to feed outhouse/work shop 63amp RCCB. (Non time delay) 40a mcb to feed outhouse plus 3 spare slots ... 6mm SWA to outhouse

OK. As has been said, if the 100A 30mA upstream RCD is not time-delayed, there's no guarantee that the RCD in this CU will prevent faults in the outhouse taking out your entire installation.

Unit four in outhouse fed from the 40a mcb via 6mm SWA. 100a disconnector with 2 16a mcb for power and 2 6a mcb for lighting.

Fair enough. Is there a reason for having two power circuits and 2 lighting ones? As has been said, it would be more conventional to have the 63A RCD in this CU in the outhouse than in the main house.

Kind Regards, John

 

[Andypease1]

Thanks for that will try to answer

The main switch is 100a 30 ma stand alone box which feeds a large terminal block from which the tails run to the three CU's . Do not think it is time delayed but do not know how to tell

Disconnectors are just red two pole swiitches in the lighting CU and no. 4 in the outhouse.

Would not the the 63amp 30ma rccb in no. 3 CU in the house feeding the out house trip before the main switch if probs in the outhouse.

Have two powers circuits a radial for the bench tools, a small heater, Hoover etc. the other is for two large freezers which permanently wired through fused outlets and wanted to keep separate.

Two lighting circuits one for strip lights and bench lights and one for security lights which get screwed up every time we have a power cut ( very rural overhead lines) sensors play up for a while

Your comments much appreciated

Best regards

 

[JohnW2]

The main switch is 100a 30 ma stand alone box which feeds a large terminal block from which the tails run to the three CU's . Do not think it is time delayed but do not know how to tell

Fair enough. Is it possible for you to post a photo or, alternatively, tell us everything which is written on it? Do I take it that it has some sort of 'test button'?

Disconnectors are just red two pole swiitches in the lighting CU and no. 4 in the outhouse.

... and presumably in the sockets/cooker one as well?

Would not the the 63amp 30ma rccb in no. 3 CU in the house feeding the out house trip before the main switch if probs in the outhouse.

As I said, by no means necessarily unless the main 100A/30mA one was time delayed. That's probably the main reason they developed time-delayed ones.

Have two powers circuits a radial for the bench tools, a small heater, Hoover etc. the other is for two large freezers which permanently wired through fused outlets and wanted to keep separate. Two lighting circuits one for strip lights and bench lights and one for security lights which get screwed up every time we have a power cut ( very rural overhead lines) sensors play up for a while

OK - fair enough. It certainly does no harm to have split circuits. I take it that the freezers are of a type suitable for use in an outhouse - seemingly ironically (unless one thinks about how they work) fridges and freezers often stop working if the ambient temperature gets too low - which is why most domestic ones come with warnings that they are not suitable for use in outhouses.

Kind Regards, John

 

[ban-all-sheds]

System will be as follows ( it is a big house)

Incoming mains to 100a 30ma main switch

3 sets of tails to 3 separate consumer units

That's awful.

It's already a very poor design to have the entire electrics for a large house on one RCD - to then go and add a supply to an outbuilding as well would be madness.

At the very least you should have your electrician replace all of the main switches in the CUs with RCDs and ditch the main one. For the SWA to the outbuilding he should fit a 300mA or a 100mA Type-S and RCBOs in the outbuilding.

 

[Andypease1]

Thanks for all your help

Will be back tomorrow and will give you details of the main switch . Yes it does have a test button

The switch in the power circuit / cooker CU is a DP 100a 30ma RCCB the red disconnector is only in the lighting CU and the aux one in the outhouse. The two main CU ' s are not split instead we have one for each in view of the large number of circuits. We have 17 rooms and loads of electrics.

Am aware about the freezers we call it an outhouse / garage but in truth it is a smart garage with insulated walls and ceiling plasterboard walls, roof lites plastic tiled floor and kitchen units for tools etc with 3.5 mtr work bench. High and low level lighting and an electric door. Took me ages and will live there when the wife throws me out!!!

Best regards
Andy

 

[Andypease1]

Thank you ban all sheds.

The power cu does have it own rccb and so will the cu for the outbuilding. The lighting unit has a disconnector as an rccb will blow every time a halogen bulb goes. It is the same as a split unit but separated into two separate units because there were more than normal circuits.

Why have RCBO's in the posh outhouse . No extraneous metal or water or gas pipes. I do have RCBO's for the shower and the pond for obvious reasons.

The outhouse cu is protected with a 63amp 30ma RCCB

The installation except the outhouse was certified when the two main CU's were installed and again by a seperate electrician when there was a major revamp and all circuits were fully tested one NEICC and the other to a different board which I can't remember . Neither had any problems.

Your comments are very welcome but seem a little harsh if I may say so.

This was a real quality installation done to an extremely high standard and also looked at by my building inspector

Best regards
Andy

 

[JohnW2]

The power cu does have it own rccb and so will the cu for the outbuilding. The lighting unit has a disconnector as an rccb will blow every time a halogen bulb goes. It is the same as a split unit but separated into two separate units because there were more than normal circuits.

That's fair enough, but the problem we've all identified (in some cases more gently than BAS) is that, unless that single upstream RCD is time-delayed, a fault anywhere, even on a circuit protected by another RCD, is at serious risk of taking out the entire installation in your large house (and I know about large houses ). (BTW, whilst dying bulbs/lamps can trip MCBs, it's pretty unlikley that they would cause an RCD to trip)

Why have RCBO's in the posh outhouse . No extraneous metal or water or gas pipes. I do have RCBO's for the shower and the pond for obvious reasons. ... The outhouse cu is protected with a 63amp 30ma RCCB

I can but presume that BAS was thinking of having RCBOs (or an RCD+MCBs) in the outhouse instead of in the CU in the house supplying it. As you imply, if you have an RCD in that CU in the house, there's no need/point in having an RCD or RCBOs in the outhouse.

The installation except the outhouse was certified when the two main CU's were installed and again by a seperate electrician when there was a major revamp and all circuits were fully tested one NEICC and the other to a different board which I can't remember . Neither had any problems. ... This was a real quality installation done to an extremely high standard and also looked at by my building inspector

How long ago was this done? As has been said, to have the electrical installation of an entire, large, house at the mercy of a single RCD seems very poor design practice, and not compliant with regulations since the current edition came into force in 2008.

Kind Regards, John

 

[Andypease1]

Hi John

Thanks for the gentle words

The first part of the installation was in 2007 when the main switch and the two main CU's were fitted. Later in about 2009 we put in new circuits for a very large extension both installations were fully tested and certified.

May be the main switch has a time delay will let you have all the details tomorrow not sure how to include a picture.

The main switch has never tripped. Halogeng bulbs have tripped the lighting circuit mcb's . A faulty toaster and a kettle both tripped the RCCB on the power CU . It also tripped when I stripped. Wall and got a socket wet. The pond RCBO trips every time you cough but that is when the rain got into the external boxes when I left them open and a pump that had a fault on it.
But as I say never the main switch.

If as at seems 1 main switch is bad practice can I ask why and what it should be like.

Regards
Andy

 

[deadshort]

m, I would repakce the main rcd with a 100a switch and fit rcbo's in cu's 1+2 and use your 63a rcd for the supply to the out building.

Regards,

DS

 

[Andypease1]

Thanks DS

To fit RCBO,s instead of mcb,s is an enormous cost especially for the Square D ones I have to be honest that seems so over the top as to be ridiculous even to me as an amature. Why on earth would you want an RCBO for a few lights in a lounge ceiling.

Regards
Andy