Using Rcbo`s Instead Of An Rcd

[redman]

Hello all,

This is just a query I was thinking about, & not an actual installation.

If i was going to install a new consumer unit in a domestic installation, a way to minimise the inconvenience of possible nuisance tripping could be to use RCBO`s instead of using a split board with 2 RCD`s.

I was thinking I would then use RCBO`s to protect every circuit, including the lighting. 

So.......presuming all this is installed, how would I test the disconnection times of the RCBO`s on the circuits that dont have socket outlets ?   such as the lighting etc.

When i`ve tested RCD`s & RCBO`s in the past, it has always been through a socket outlet which is being protected by that device.

Any suggestions ?

Cheers.

 

[steptoe]

mmmmm

at the terminals?

you shouldnt be testing any RCBO or RCD at any point other than source,

as for the ones where the terminals are before the coil, try a jump lead.

 

[ProDave]

You should test the rcd trip times at the board, that's what I do regardless of whether it's an rcd or rcbo.

 

[NozSpark]

...... with the circuits disconnected as well

 

[redman]

At college I was taught that at this point of live testing, all covers should be in place on the consumer unit & accessories.

Then to prevent touching live parts, test the RCD at a socket outlet that it protects.  (using the plug in lead with the multi function tester)

X  1

X  5

X  0.5

This is the only way I`ve ever done it.

 

[ProDave]

ELF N Safety?

That's what insulated probes are for.

 

[Andy™]

At college I was taught that at this point of live testing, all covers should be in place on the consumer unit & accessories.

there is a difference between college and the real world. which is why proper training should be an apprenticeship with someone who knows what they are doing, not just quickly learning enough to pass an exam (although you dont state what training your getting, it may well be an apprenticeship but unlikely)

 

[redman]

there is a difference between college and the real world. which is why proper training should be an apprenticeship with someone who knows what they are doing, not just quickly learning enough to pass an exam (although you dont state what training your getting, it may well be an apprenticeship but unlikely)

Im currently serving a 4 year [SIZE=medium]apprenticeship. [/SIZE]

[SIZE=medium]T[/SIZE][SIZE=medium]he majority of my work involves working on  large commercial building projects that can last over twelve months.[/SIZE]

[SIZE=medium]Its quite rare for me to get any hands on testing experience on these jobs, as they involve alot of installation time. [/SIZE]

[SIZE=medium]However, I have seen the method I descibed above, used for testing RCD`s in the real world. [/SIZE]

[SIZE=medium]So,  I always thought this was the correct way to do it.[/SIZE]

 

[Andy™]

fair enough. you should be testing RCD's at the terminals and in isolation, although it is common practice to test at a socket if available. failing that, its probes on the terminals

 

[redman]

OK,

Thanks for your help guys

 

[ProDave]

And don't forget the forum sponsor that specialises in rcbo cu'c

http://www.talk.electricianforum.co.uk/topic/22663-sbs-trade-sales/

 

[SBS Dave]

Hi ProDave and Canoeboy, thanks for mentioning my products and location on the Forum,

Hi Redman, when you do get a job that needs circuit protection, I hope you will give my products a try.

With regard to live testing, the proper place to to RCDs/RCBOs is at the board, but I could see it may be difficult with the lid on the CU.

Where did the College suggest you test Ze, ZL, pfc and ssc? If it is dangerous to test RCDs at the board, it is no less dangerous to test Ze, etc.

SBS Dave

 

[SPECIAL LOCATION]

Hello all,

This is just a query I was thinking about, & not an actual installation.

If i was going to install a new consumer unit in a domestic installation, a way to minimise the inconvenience of possible nuisance tripping could be to use RCBO`s instead of using a split board with 2 RCD`s.

I was thinking I would then use RCBO`s to protect every circuit, including the lighting. 

So.......presuming all this is installed, how would I test the disconnection times of the RCBO`s on the circuits that dont have socket outlets ?   such as the lighting etc.

When i`ve tested RCD`s & RCBO`s in the past, it has always been through a socket outlet which is being protected by that device.

Any suggestions ?

Cheers.

Read bullet point 11.1,  "general test procedure"

Chapter 11, Page 106 of On Site guide..

Testing RCD's..

see where BS7671 guidance suggests

:innocent

 

[Technician]

The other thing to bear in mind is that only 30mA

RCD's/ RCBO's are tested at

 

[apprentice87]

I wonder if in college they tell car mechanics that a car engine must always be off unless the bonnet is closed????

john...

 

[Steve3948]

I understand why so many people do it different, when I was at college (many many years ago) they said test RCD at furthest point.

The idea behind that was that if it tripped within required time it would be good everywhere else.

Then it was test at the RCD and then with circuits disconnected.

I tend to do it at the board, but now then at a socket, and sometimes check both just to see difference, and it's always still within acceptable parameters, give or take a millisecond or two. 

 

[adammid]

NICEIC state that the preferred point of measurement is at a socket outlet. 'Niceic guide to domestic periodic Inspection, Testing and Reporting' chapter 5 page 306

 

[Sidewinder]

Once again the NIC think they are better than, and go against the IET regs & manufacturers statements.

They also are ignoring the fundamental physics behind this, the measurement taken at a socket outlet WILL be different to that at the output terminals of the device, that is a fact that cannot be discounted.

That is according to the laws of physics.

2.7.18 in GN3 "applies".

There is also the instrument standard BS EN 61557-6 to consider.

I've not checked 61557-6 to see what it says, but it is the instrument standard.

However, testing at a socket outlet, will prove that the RCD functions "in circuit" within the requirements of the regs, but, there can be issues with this method.

 

[Andy™]

NICEIC state that the preferred point of measurement is at a socket outlet. 'Niceic guide to domestic periodic Inspection, Testing and Reporting' chapter 5 page 306

nic guideline, is just that, a guideline. they do not write the regs. they just think they do

 

[Steve3948]

Perhaps they should