RCCB as main switch?

[Guest77]

It may well be one of these chuckle, and the OP is confused.

 

[Guest125]

From the description , and without looking at it !
I would say that the installation is likely to be TT , hence the up front rcd ( probably an 100mA S type ) so why or how could it possibly be failing any regs if the new circuit was to be just installed on a new rcbo ( even then if needed ? ) , instead of a whole new board !?

My point was the opposite. To not install a MCB but an RCBO.

 

[davesparks]

You can't get 30ma time delayed RCD or RCBO. He needs to say what he has got.

Can't you?

 

[Guest125]

find me one!

And when I do?

 

[Simlec]

Yes you can.

Where would you use one?
I know where you find them, next to the rocking horse sh*t lol

 

[telectrix]

And when I do?

shove it up your **** :49:

 

[Guest125]

My point was if he installs a new circuit to a board which has a RCD main switch (and doesn't need it) then in affect he will be making the existing circuits worse by adding to the problem of one RCD protecting the whole installation. I know it is not clear cut and is only my interpretation so I think a board change would ensure all the new work is compliant.

 

[JD6400]

find me one!

I had this about 2 years ago , someone on here had found one on fleabay just to prove a point . :dunce2:
Despite it being from some knock off 3rd world importer , I still had to go to the trouble of explaining why it was as much use as ---- on a bull !

 

[davesparks]

Where? Think you will be looking a while

Well for a start a simple adjustable RCD will give you tripping currents from 10mA up to 1A (or more) and time delays of 0.1S up to 10S (or more)

 

[TJ Anderson]

Can't you?

Not that I am aware, have you?

 

[Guest77]

Not that I am aware, have you?

What make would you like?

 

[Guest125]

Well for a start a simple adjustable RCD will give you tripping currents from 10mA up to 1A (or more) and time delays of 0.1S up to 10S (or more)

Plus a company called FDB will manufacture any RCD to any specification. We use them a lot for DC immune RCDs.

 

[telectrix]

My point was if he installs a new circuit to a board which has a RCD main switch (and doesn't need it) then in affect he will be making the existing circuits worse by adding to the problem of one RCD protecting the whole installation. I know it is not clear cut and is only my interpretation so I think a board change would ensure all the new work is compliant.

i agree, but you border on persuading the customer to spend more than necessary if a less costly solution is available whilst still leaving the installation safe. a bit like condemning 3036 boards because they're not to current standards, although safe for continued use.

 

[davesparks]

Where would you use one?
I know where you find them, next to the rocking horse sh*t lol

Main and sub distribution units used for temporary power distribution in outdoor events will often incorporate adjustable RCDs which can be set to give 30mA time delayed operation along with a whole host of other possible settings.

Most rental generators now have adjustable RCD protection as standard too.

 

[davesparks]

Not that I am aware, have you?

I've never used a fixed 30mA S type, but plenty of adjustable ones that could give that kind of operation. And I am sure it wouldn't take me long to find one if I needed one.

 

[Guest125]

i agree, but you border on persuading the customer to spend more than necessary if a less costly solution is available whilst still leaving the installation safe. a bit like condemning 3036 boards because they're not to current standards, although safe for continued use.

Safety first

 

[TJ Anderson]

What make would you like?

MK, Crabtree, Wylex, BG, or Hager please

 

[JD6400]

Main and sub distribution units used for temporary power distribution in outdoor events will often incorporate adjustable RCDs which can be set to give 30mA time delayed operation along with a whole host of other possible settings.

Most rental generators now have adjustable RCD protection as standard too.

Hi Dave

But why would you want to set it at 30mA delayed as opposed to 100mA delayed , as by delaying it you will have lost the benefit of the 30mA anyway ?
Is this something to do with the regs you have to follow for events

 

[davesparks]

find me one!

Take one of these www.hobut.co.uk/earth-leakage-relays , add a suitable core balance CT and connect to a shunt trip on an MCB or MCCB of your choice.

 

[TJ Anderson]

Ok. I think we can safely say the OP's client will not have a bespoke "specialist order" variable ma RCD on the front end of his install. More like a crusty old 60A Crabtree ELCB that don't trip when the button is pressed!!

 

[davesparks]

Hi Dave

But why would you want to set it at 30mA delayed as opposed to 100mA delayed , as by delaying it you will have lost the benefit of the 30mA anyway ?
Is this something to do with the regs you have to follow for events

To ensure discrimination with 10mA RCDs installed downstream of it. The same way you would use 100mA S type in front of 30mA in a TT setup. It depends entirely on what it is protecting and why.
You are building installations out of pre-built standard distribution boards unlike fixed installations so you almost always end up with multiple RCDs in series. Sometimes you have to set one as a 30mA time delay just to stop a fault on one circuit from tripping out 2 or 3 RCDs upstream of it but still give discrimination with a 100mA upstream of that.


There is no regulatory reason for using them though, just the individual electricians design/method for ensuring that faults cause minimum disruption.

 

[davesparks]

Ok. I think we can safely say the OP's client will not have a bespoke "specialist order" variable ma RCD on the front end of his install. More like a crusty old 60A Crabtree ELCB that don't trip when the button is pressed!!

No he won't, but you stated that such things do not exist, so those of is who know better have disagreed.

 

[Noob2013]

I will have a look at the RCD when I go back and update you all.

It looked like a fairly new RCD with a test button. Definately not 10+ years old! Also no adjustments available on it.

So the general verdict is;

If it's a 30mA RCD then use an MCB for new circuit.

and

If it's 100mA RCD then use a 30mA RCBO for new circuit?

 

[Guest77]

MK, Crabtree, Wylex, BG, or Hager please

I could easily get my wholesaler to find one, a quick google and I found a protec, MK do one as well if you look throught their range in the catalogue
[h=1]RCD, DP 2 Module Time Delay[/h]

Catalogue No1:	T100-30-2TD
Size:	100A 30mA
Range:	Circuit Protection RCDs

 

[Guest125]

it is not quite that clear cut. You will need to interpret the regs on this one as there is a little disagreement.

I would say to be 100% sure just change the board. You cannot be wrong then. Other methods are open to a little interpretation.

Prepare 2 quotes and give the customer the pros and cons of both.

 

[Guest125]

Mental note: "Never say you can't"

 

[JD6400]

it is not quite that clear cut. You will need to interpret the regs on this one as there is a little disagreement.

I would say to be 100% sure just change the board. You cannot be wrong then. Other methods are open to a little interpretation.

Prepare 2 quotes and give the customer the pros and cons of both.

Or go and check what is there and then quote . I would say it is still a little early for building up the old bank balance ready for next christmas ! mg_smile:

 

[JD6400]

To ensure discrimination with 10mA RCDs installed downstream of it. The same way you would use 100mA S type in front of 30mA in a TT setup. It depends entirely on what it is protecting and why.
You are building installations out of pre-built standard distribution boards unlike fixed installations so you almost always end up with multiple RCDs in series. Sometimes you have to set one as a 30mA time delay just to stop a fault on one circuit from tripping out 2 or 3 RCDs upstream of it but still give discrimination with a 100mA upstream of that.


There is no regulatory reason for using them though, just the individual electricians design/method for ensuring that faults cause minimum disruption.

Thanks for that Dave , always good to see the reasoning behind how it is done in different sectors of our industry .
I can see how it would give you some discrimination if the fault was not to large .

 

[davesparks]

Thanks for that Dave , always good to see the reasoning behind how it is done in different sectors of our industry .
I can see how it would give you some discrimination if the fault was not to large .

With the time delay being selectable you can get a fairly good discrimination between multiple RCDs used for fault protection.

At the end of the day in this part of the industry it is going to boil down to doing the best you can when you're up to your knees in mud in the middle of nowhere.

 

[Noob2013]

With the time delay being selectable you can get a fairly good discrimination between multiple RCDs used for fault protection.

At the end of the day in this part of the industry it is going to boil down to doing the best you can when you're up to your knees in mud in the middle of nowhere.

So a 30mA time delayed RCD with a standard 30mA RCBO would be acceptable?

 

[davesparks]

So a 30mA time delayed RCD with a standard 30mA RCBO would be acceptable?

Sorry, we've gone off at a bit of a tangent there talking about temporary distribution for events.

It would be utterly pointless in an installation, the cost would be ridiculous for a start

 

[Simlec]

Main and sub distribution units used for temporary power distribution in outdoor events will often incorporate adjustable RCDs which can be set to give 30mA time delayed operation along with a whole host of other possible settings.

Most rental generators now have adjustable RCD protection as standard too.

So when you have your 30mA time delayed Setup, what is it protecting ?
As the max for personal shock protection is 30mA.
Your 10mA RCDs on final circuits will protect life in damp/wet areas for your outdoor event.

 

[Guest125]

With the time delay being selectable you can get a fairly good discrimination between multiple RCDs used for fault protection.

At the end of the day in this part of the industry it is going to boil down to doing the best you can when you're up to your knees in mud in the middle of nowhere.

I think there is going to be a lot of change in this sector in the 3rd AMD.

 

[davesparks]

I think there is going to be a lot of change in this sector in the 3rd AMD.

No there won't, nobody gives two hoots about what 7671 has to say!

 

[baldsparkies]

Until all facts and that deffo includes earthing arrangement are known.
A definitive answer can't be given.
So everything so far is surely hypothetical which could mean another long thread lads.

 

[Guest125]

Until all facts and that deffo includes earthing arrangement are known.
A definitive answer can't be given.
So everything so far is surely hypothetical which could mean another long thread lads.

Yeah but all these threads cannot give every detail and any advice should be verified by the installer anyway.

I like to think of it as a chat amongst collegues at lunch.

 

[Guest125]

No there won't, nobody gives two hoots about what 7671 has to say!

Present company excluded no?

 

[baldsparkies]

Yeah but all these threads cannot give every detail and any advice should be verified by the installer anyway.

I like to think of it as a chat amongst collegues at lunch.

Or killing time before going to bed because there's FA worth watching on the telly.

 

[davesparks]

So when you have your 30mA time delayed Setup, what is it protecting ?
As the max for personal shock protection is 30mA.
Your 10mA RCDs on final circuits will protect life in damp/wet areas for your outdoor event.

It's protecting other parts of the site from losing power when a fault occurs downstream of it.

Damp/wet areas? We're talking about outdoor events in the UK, we'll be lucky if it's merely damp! Torrential rain is far more likely.

 

[davesparks]

Present company excluded no?

Not really, I'll consider the requirements of 7671 and 7909 a bit more than most do but I sure as hell don't stick to them as if they were gospel!

 

[PEG]

Not really, I'll consider the requirements of 7671 and 7909 a bit more than most do but I sure as hell don't stick to them as if they were gospel!

Oh no,did you just say "Jehovah"?....I'll go and get some pebbles...:icon12:

 

[Guest125]

Not really, I'll consider the requirements of 7671 and 7909 a bit more than most do but I sure as hell don't stick to them as if they were gospel!

You sound like great company Dave. Fancy a beer sometime?

 

[Pete999]

Hi Noob,

A new circuit would need notifying under Part P of the building regs. As your profile shows that you're an apprentice you could maybe undertake this job with one of the electricians that you work with.

Also, if you don't already have it, get yourself access to the trainees forum.

Good advice

 

[Guest125]

Reg number please?

531.2.5 - An RCD shall be so selected and the electrical circuits so subdivided that any protective conductor current which may be expected to occur during normal operation of the connected load(s) will be unlikely to cause unnecessary tripping of the device.

And:

314.1 - Every installation shall be divided into circuits, as necessary, to:

(i) avoid danger and minimise inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of hazards that may arise from the failure or a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor (PE) currents not due to a fault
(v) mitigate the effects of electromagnetic disturbances (see also chapter 44)
(vi) prevent the indirect energising of a circuit intended to be isolated.

 

[Simlec]

531.2.5 - An RCD shall be so selected and the electrical circuits so subdivided that any protective conductor current which may be expected to occur during normal operation of the connected load(s) will be unlikely to cause unnecessary tripping of the device.

And:

314.1 - Every installation shall be divided into circuits, as necessary, to:

(i) avoid danger and minimise inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of hazards that may arise from the failure or a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor (PE) currents not due to a fault
(v) mitigate the effects of electromagnetic disturbances (see also chapter 44)
(vi) prevent the indirect energising of a circuit intended to be isolated.

Not fault current.
the second one basically just means don't put everything on one circuit.

 

[Guest125]

Not fault current.
the second one basically just means don't put everything on one circuit.

(i) avoid danger and minimise inconvenience in the event of a fault

This one is as clear as a bell.

 

[SPARTYKUS]

UKESrail

I think the point being made is that these Regs youve found are all admirable but they are not retrospective! The point has already been made (the analogy with a car from the past for example, without ABS).

when you quote for a job you do not have to "fix everything".

As a further example, if you fit a plastic CU today, and it turns out from the new amendment onwards all CUs need to be steel, are you then going to go back and insist they change the one you fitted a few months back?

Catch my drift?

not sure if you are on the wind up.......

 

[Guest125]

UKESrail

I think the point being made is that these Regs youve found are all admirable but they are not retrospective! The point has already been made (the analogy with a car from the past for example, without ABS).


when you quote for a job you do not have to "fix everything".

As a further example, if you fit a plastic CU today, and it turns out from the new amendment onwards all CUs need to be steel, are you then going to go back and insist they change the one you fitted a few months back?

Catch my drift?

not sure if you are on the wind up.......

Not at all.

1) The guy asked simply for the reg which I have stated.

2) My issue with the regs not being retrospective (which I fully accept is the case) is that you will need to know exactly (1) when that specific reg came into force. and (2) when the installation and subsequent alterations were carried out.

The first of these is not impossible to find out but would take days to verify beyond doubt and the 2nd will be impossible to state and would be a guess at best. The car example you gave does not work in reality because the V5 document will always have a date on. An electrical installation without all the certificates and reports made available is anyone's guess.

I do not like to work on guess' and would rather be 100% sure that I am doing the right thing. I know there is interpretation in this but this is my humble opinion.

 

[Guest125]

Not at all.

1) The guy asked simply for the reg which I have stated.

2) My issue with the regs not being retrospective (which I fully accept is the case) is that you will need to know exactly (1) when that specific reg came into force. and (2) when the installation and subsequent alterations were carried out.

The first of these is not impossible to find out but would take days to verify beyond doubt and the 2nd will be impossible to state and would be a guess at best. The car example you gave does not work in reality because the V5 document will always have a date on. An electrical installation without all the certificates and reports made available is anyone's guess.

I do not like to work on guess' and would rather be 100% sure that I am doing the right thing. I know there is interpretation in this but this is my humble opinion.

Also I would add that many lesser sparks installed 'front end' RCDs when the 17th Edition came out in an attempt to afford the installation adequate protection. So it is not unreasonable to suggest that some 'front end' RCDs have been fitted recently.

 

[Simlec]

(i) avoid danger and minimise inconvenience in the event of a fault

This one is as clear as a bell.

Not at desk at mo so no books, but how do you explain the picture near the front of your OSG regarding TT installs with a single RCD upfront? Or do you think the IET have made a mistake?