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[bulby]

Hi

if i attend a house with bs3036 fuses what will the protection be EEBADS or ADS?

If its a 30amp fuse its a 0.4 s disconnection time , is this correct?
I am wiring a spur onto an exsisting ring main, just trying to get my head round the minor works cert

 

[DurhamSparky]

ads.... its the new terminology!!!

 

[bulby]

The new terminology, do i still have to get a 0.4 s disconnect time from a 30a bs3036?

 

[MarkieSparkie]

The new terminology, do i still have to get a 0.4 s disconnect time from a 30a bs3036?

Yes for a TN system. In order to achieve this your measured Zs <= 0.9 Ohms (OSG, Appendix 2,Table 2A)

 

[bulby]

what if my zs is higher how do i rectify the situation ?

 

[alli]

What is the earthing system? If it is TT then Zs could be high, up to 1667 ohms is allowed though it should be as low as possible. If it is TT then a 30mA RCD should be fitted which compensates/allows the Zs to be higher than stated in the tables.

 

[ackbarthestar]

What does the 30A BS3036 feed?
1/ If its a socket radial or small ring you could down rate the fuse to 20A (Yellow).
2/ You could increase the R2 by cross bonding to other circuit cpcs.
3/ If it is a TT system then there will be, or should be, a RCCB/Main Isolator at the origin of the installation which will give you a large amount of Zs leaway.

The original system should be designed to EEBADS, but that will mean main and supplementary bonding is in place. ADS is basically the same but also allows the use of other methods of protection such as RCDs and RCMs

 

[Plonker 3]

.
2/ You could increase the R2 by cross bonding to other circuit cpcs.

Please tell me you are not being serious

 

[ackbarthestar]

Please tell me you are not being serious

Perfectly serious.

Have you heard of cross bonding?

and it doesn't have to be just the cpcs to create parallel earth paths.

Why do you think it states on the BS951 clip 'Safety Electrical Connection. Do Not Remove' ?

 

[Plonker 3]

So what happens when the circuit C.P.C gets removed/ disconnected when it is no longer needed? The whole circuit that was relying on it is compromised.

The only proper way to increase r2 is by putting a larger C.S.A cable in.

 

[morph]

So what happens when the circuit C.P.C gets removed/ disconnected when it is no longer needed? The whole circuit that was relying on it is compromised.

The only proper way to increase r2 is by putting a larger C.S.A cable in.

or supplementary bonding to reduce zs

 

[Plonker 3]

But that isn't a guarenteed earth connection. What if the incomers to those bonded surfaces are later changed to plastic?

 

[ackbarthestar]

So what happens when the circuit C.P.C gets removed/ disconnected when it is no longer needed? The whole circuit that was relying on it is compromised.

The only proper way to increase r2 is by putting a larger C.S.A cable in.

Firstly, Why would anybody remove a circuit cpc?

Secondly, If you are referring to another circuit being used as a parallel path which has then become redundant then I would expect this to be picked up by the sparks doing the alterations.

It is still good practice to link cpcs across different circuits particularly in bathrooms, and recognized by the IET, to ensure low touch voltages under fault conditions. RCDs can sometimes fail.

 

[Plonker 3]

Because the general public don't understand what they are doing, say you connected you parallel earth to a single socket on its own circuit and "Fred" wanted it removing but said why should I get a spark to do it when I can do it my self, there goes your parallel earth path and your circuit is compromised.

Where in the regs does it state any of that? That may have been in the the 16th edition when you bonded virtually everything.

So you are admitting that things can go wrong like a RCD failure, unfortunately that is something we can not account for when installing them, other wise we wouldn't carry out testing as it would be pointless.

 

[bulby]

its a tns system

 

[ackbarthestar]

Because the general public don't understand what they are doing, say you connected you parallel earth to a single socket on its own circuit and "Fred" wanted it removing but said why should I get a spark to do it when I can do it my self, there goes your parallel earth path and your circuit is compromised.

Where in the regs does it state any of that? That may have been in the the 16th edition when you bonded virtually everything.

So you are admitting that things can go wrong like a RCD failure, unfortunately that is something we can not account for when installing them, other wise we wouldn't carry out testing as it would be pointless.

So you are now advocating that 'Fred' who knows I MUST NOT SWEAR ON AN OPEN FORUM all about electrical installations should do the work himself rather than employing a competent person? ....... no, of course you're not, that would be irregular and would probably affect an insurance claim if it could be shown that Mr Numpty had buggered up the electrics.

Reference to cross bonding is explained in GN8. EEBADS has been around as long as there has been the necessity for automatic disconnection under earth fault conditions. RCDs are comparatively new invention to domestic electrical installations, although residual currents and voltage detection for earth fault interruption designs have been sitting on someones desk since the 1920's.

RCDs cover a multitude of sins, motor cars get us independently from A to B, that doesn't mean that they don't fail from time to time

 

[Engineer54]

Because the general public don't understand what they are doing, say you connected you parallel earth to a single socket on its own circuit and "Fred" wanted it removing but said why should I get a spark to do it when I can do it my self, there goes your parallel earth path and your circuit is compromised.

Where in the regs does it state any of that? That may have been in the the 16th edition when you bonded virtually everything.

So you are admitting that things can go wrong like a RCD failure, unfortunately that is something we can not account for when installing them, other wise we wouldn't carry out testing as it would be pointless.

Using your own analogy from your last paragraph, what is different to your example in your first paragraph?? You have no control what Fred does, so you cannot cater for his actions, just like you can't foresee an RCD failing at some point in the future.