My last 'non Amd 3' CU Install.

[bigspark17]

Haha I see what you mean mate, it does look a bit like that !:laugh3: Found another of my little jobs from around 3-4 years ago, this was an old house undergoing total refurbishment, unfortunately the idiot builder plastered the wall where the CU is before the cables coming down from above were in place [a load coming up from floor level were in oval conduit due to exposed beams in that room and no wiring allowed 'on show'] but the owner was putting a cupboard there anyway. That was a nice old house to work on, right out in the wilds and most of the time I was there alone, a really tranquil place. :smiley2: View attachment 31019View attachment 31018

as previously asked is this a tt system? Theres no dno earth and you havent got a rcd main switch at origin.?

 

[Leesparkykent]

as previously asked is this a tt system? Theres no dno earth and you havent got a rcd main switch at origin.?

What makes you think it's TT? I'm viewing the pic on an iPhone so you may be able to see a bigger pic on another device but I can't see a head in the pic to determine wether it's a DNO supplied earthing arrangement. You can see a 16mm Earth though....even it was a TT system why does it require an RCD as the main switch? It's a dual RCD board...It may be prudent to have an S-type upfront but not an actual requirement. Could you post a few pics of a recently completed CCU you have done?

 

[Midwest]

If it is a TT supply, the meter tails are run on the surface & are entering an insulated CU. All the circuits appear to have additional protection via RCD. Why would it need RCD main switch at origin? Take it you mean a S type RCD?

Edit: beaten by Lee

 

[Amp David]

Looks like TT.

But why the need for and RCD at origin? Looks like an insulated CU

 

[Leesparkykent]

I must be looking at the wrong pic anyway haha

 

[Deleted member 9648]

as previously asked is this a tt system? Theres no dno earth and you havent got a rcd main switch at origin.?

Perhaps you'd care to explain why an RCD main switch is needed in this instance?

 

[shanky887614]

nothing wrong with using a non amd3 board as long as it is within a non readily combustable enclosure its fine

 

[bigspark17]

If it is a TT supply, the meter tails are run on the surface & are entering an insulated CU. All the circuits appear to have additional protection via RCD. Why would it need RCD main switch at origin? Take it you mean a S type RCD?

Edit: beaten by Lee

well i was always taught and still belive all tt system should have upfront rcd at origin for fault protection, if you are relying on the 30mA rcd in these mass produced dbs then althought ok to cover your own arse at install what happens in the future when these low end rcd's break down and the originalsinstallers poor tt 3/8 rod degrades leaving unacceptavle Ra to operate overload device within disconection times, the install is then in a very unsafe state for the building and user! Why has the op not stated if this is a TT and could shed more light on the install in question

 

[telectrix]

years ago, it was common to fit an upfront RCD to a TT system for fault protection where some or most of the circuits were not RCD protected. with the introduction of the 17th ed. now all circuits ( in a domestic property) are generally on RCD since the "buried<50mm deep" reg. came into force. now it's genarally accepted that the CU RCD/s will give that fault protection.

 

[bigspark17]

So this rcd could be leaving the install in a dangerous state untill the next test, and the next test always gets done on due date lol. I stick to my guns a 100mA type S upfront on a domestic TT at origin is the best way to install that system

 

[shanky887614]

So this rcd could be leaving the install in a dangerous state untill the next test, and the next test always gets done on due date lol. I stick to my guns a 100mA type S upfront on a domestic TT at origin is the best way to install that system

how? it is relatively easy in a lot of places to get a really low ra so why is an additional rcd needed in all cases

 

[Simonslimline]

What a shocking end product.? If i left that sort of end product with my customers id have none left, funny how standards differ from one end of Country to other!!

Any chance of uploading a photo/s of the standard of your work?

Maybe we can all learn something.

:sifone:

 

[telectrix]

nobody's disputing that it's the best way, just not required by regs.

 

[hightower]

So this rcd could be leaving the install in a dangerous state untill the next test, and the next test always gets done on due date lol. I stick to my guns a 100mA type S upfront on a domestic TT at origin is the best way to install that system

Why type s? I thought 100ma would offer enough discrimination from a 30ma? Read somewhere 3 times as much, so for discrimination 90ma or higher should act independently without the need for a time delay

 

[Midwest]

So this rcd could be leaving the install in a dangerous state untill the next test, and the next test always gets done on due date lol. I stick to my guns a 100mA type S upfront on a domestic TT at origin is the best way to install that system

As Tel says, believe this was a common design a few years ago and perhaps a few sparks still use it. You may find that difficult with A3? The same could be said of the reliability of MCB's, at least an RCD can be tested. What if the S type goes faulty, how do you design that out

 

[Simonslimline]

Why type s? I thought 100ma would offer enough discrimination from a 30ma? Read somewhere 3 times as much, so for discrimination 90ma or higher should act independently without the need for a time delay

Where did you hear that mate?

Should be S type.

 

[Midwest]

Why type s? I thought 100ma would offer enough discrimination from a 30ma? Read somewhere 3 times as much, so for discrimination 90ma or higher should act independently without the need for a time delay

Can't give you the science others will, but time delay rcd is a better design, as I've been advised before.

 

[hightower]

Where did you hear that mate?

Should be S type.

Will have a flick through my books and see if I can dig it out

 

[shanky887614]

hightower i recommend you have a look on google at discrimination. if you have a 100ma ac rcd and then a 30ma ac rcd they will both trip at once on fault.


an s type or time delayed is recommended because it allows any rcd's/mcbs down stream to clear the fault without tripping.

130-500ms for wylex s type rcd.

 

[davesparks]

Why type s? I thought 100ma would offer enough discrimination from a 30ma? Read somewhere 3 times as much, so for discrimination 90ma or higher should act independently without the need for a time delay

An S type is used to ensure discrimination in all cases as far as possible.
Without a time delay fault currents could easily cause both devices to operate simultaneously. Also any background earth leakage on individual circuits could add together to bias the 100mA to trip first without the time delay.