'17th CU' thread

[skenk]

Why was it locked?

My undertanding is a CU change means you take responsibility for all circuits and as such they would need to be up to 17th standards. A dual RCD board could be suitable for this as long as both RCD's were 30ma and there was a main isolator.

 

[sealeon]

1 REG 411.3.3 2 REG 701.411.3.3 3REG 522.6.6.8 4REG 314.1 5REG 314.2 So I would say a board with seperate rcbo s for all cicuits would be the only way to fully comply with 17th edition.

 

[Pensdown]

My argument is quite simple, as is the explanation, justification etc.

If you cannot prove that cables are routed to comply with 522.6.6, you have to assume that they aren't and thus 522.6.7 is required.

How hard is that?

Most sparks carry out a PIR before doing a CU change and for an existing installation non-compliance with 522.6.6 would be a code 4.

So IYOP why does it change to a code 2 if the CU is changed?

 

[GaryMo]

It seems I've missed something but....

By changing the Consumer Unit (and the OPD for every final circuit) you would then comply with 522.6.6 / 522.6.7 as surely you would either install a twin RCD board or use RCBO's for all circuits that require them, wouldn't you? I would.

 

[Pensdown]

You've only missed the usual polite conversation between some posters. If you read the locked post all will become clear.

 

[ban-all-sheds]

Why was it locked?

My undertanding is a CU change means you take responsibility for all circuits

But do you? Or do you only take responsibility for the work that you do?

And what does "take responsibility" mean? To what extent can you take responsibility for the compliance of circuits you didn't install?

OK - you can check continuity and IR, and you can assume that nothing is so deep that RCDs aren't needed, if you believe that you need to in the first place, but you can't be sure there are no undersized sections, you can't be sure there aren't Band I and Band II circuits in the same enclosures, you can't be sure the cables are all in the correct zones and so on and so forth.

and as such they would need to be up to 17th standards.

So there are limits to what "responsibility" you can take - are there also factors which affect if you should?

For example - you say replacing the CU triggers responsibility, and thus, for example, RCDs.

What about replacing just a faulty MCB?

What if you had a rewirable CU with a circuit was on a fuse that was too big, and the customer was OK with you putting the right rewirable in, but wouldn't pay for CU replacement or an outboard RCD - would you refuse to do the work?

What about adding a spur? You could ensure compliance of your bit of cable by using conduit or BS8436 etc - do you think you have to bring the existing circuit up to 17th requirements?

 

[GaryMo]

My undertanding is a CU change means you take responsibility for all circuits

But do you? Or do you only take responsibility for the work that you do?

You carry out a PIR prior to changing the consumer unit to verify that rating and condition of existing equipment including all earthing and bonding arrangements will be adequate.
You can't change a consumer unit and just complete an EIC covering the board and main tails without thought for the final circuits which you're altering (by changing their OPD) and putting back into service.

 

[FingRinal]

I think the correct answer lies in whether you are a DIYer or a professional electrician.

I have yet to speak to an electrician who is a membr of any organisation that would agree with BAS (a DIYer). I'm afraid, whether anyone likes it or not, it's a fact. I think it's because of 131.8.

It is very easy to nit pick at the Regs and segue into clever arguments. Clever, but pointless if the sole reason is just to harp on.

Now, I don't believe in slavish adherence to the strict letter of the Regs. As such, I believe there might be situations when 131.8 might be overlooked.

Example:

A consumer unit or fuseboard has been smashed by burglars, is hanging off the wall with dangerous exposed conductive parts. The only damage is to the CU. An electrician is called and installs an emergency replacement.

This seems to be at odds with the strict observance of 131.8. But correcting the fault and removing the danger of exposed conductive parts and the danger of direct contact with such parts is to me the greater priority.

A consumer unit replacement however, can be considered nothing other than 'planned works'. As such, (in my opinion) there is no justification for anything other than strict observance of 131.8.

So, I agree with GaryMo on this.

Of course, a DIYer can do anything he or she wants to do. Afterall, who would know?

But a professional electrician offering a professional level of service, such DIY thinking should never be a part of their function as a law-abiding, Regs-abiding, professional electrician.

 

[atm]

this is, i hope relevant to the thread.

i am putting in a new board as my job for mr napit.

the customer wants a hot tub and i do not want to put it on the existing wired fuse board. i could put in a second 1 way rcd board to run the hot tub but the customer is happy for the full upgrade and it saves me messing with the main fuse to split the tails.

The gas is bonded but the water is not. stop clock is in their bathroom and a long way off from the MET and a fat green and yellow cable running through their front porch is turning their stomachs. this is a TT system.

1, can i bond the water with a earth spike?
2, holmslaw mentioned that for TT only a dual RCD board will surfice, have looked in my book and cannot find the reason for this, please can someone advise!

assuming after my initial tests the IR and loop tests work out ok is there any reason why i should not do this?

your individual respected opinions are most appreciated thanks.

 

[FingRinal]

this is, i hope relevant to the thread.

i am putting in a new board as my job for mr napit.

the customer wants a hot tub and i do not want to put it on the existing wired fuse board. i could put in a second 1 way rcd board to run the hot tub but the customer is happy for the full upgrade and it saves me messing with the main fuse to split the tails.

If you're putting in a new board, why not put the hot tub on it?

The gas is bonded but the water is not. stop clock is in their bathroom and a long way off from the MET and a fat green and yellow cable running through their front porch is turning their stomachs. this is a TT system.

1, can i bond the water with a earth spike?

No. It needs to be bonded back to the MET, the same as the other bond.

2, holmslaw mentioned that for TT only a dual RCD board will surfice, have looked in my book and cannot find the reason for this, please can someone advise!

Take your guidance from BS7671 and the OSG. A 17th Edition CU won't necessarily comply with 314, but if you arrange the circuits correctly it should do.

assuming after my initial tests the IR and loop tests work out ok is there any reason why i should not do this?

It would be incorrect to do it.

 

[davy_owen_88]

1, can i bond the water with a earth spike?
2, holmslaw mentioned that for TT only a dual RCD board will surfice, have looked in my book and cannot find the reason for this, please can someone advise!

You can NOT 'bond' to an earth rod. The whole point of equipotential bonding is to keep metalwork at the same potential in the event of a fault. Installing another earth rod and bonding water pipework to that is going to create potential differences that is potentially lethal. You must run the bonding conductor back to the main earth terminal, nothing else is acceptable.

TT supplies rarely have Zs readings below the required levels to enable disconnection via MCB's. For this reason RCDs with an operating current of not more than 30mA must be used. It is poor practice to protect an entire installation with only one RCD because a fault on one circuit will knock out the entire house so splitting the circuits between 2 or more RCD's minimises the inconvenience. RCBO's are better

 

[GaryMo]

i am putting in a new board as my job for mr napit.

1, can i bond the water with a earth spike?

Please don't take this the wrong way but do you think you're ready?
What you're asking is such a basic question.

 

[ban-all-sheds]

I think the correct answer lies in whether you are a DIYer or a professional electrician.

I'm surprised that you think that different wiring regulations apply, or apply in different ways, to DIYers.

I have yet to speak to an electrician who is a membr of any organisation that would agree with BAS (a DIYer).

All I've done is ask questions.

I'm afraid, whether anyone likes it or not, it's a fact. I think it's because of 131.8.

So it's a fact, but you only think you know why it's a fact?

It is very easy to nit pick at the Regs and segue into clever arguments. Clever, but pointless if the sole reason is just to harp on.

I'm not asking anybody to nit-pick, just asking questions about what people believe to be the extent of their "responsibility" etc.

Now, I don't believe in slavish adherence to the strict letter of the Regs. As such, I believe there might be situations when 131.8 might be overlooked.

Example:
.
.

What of the examples I listed?

Would you refuse to make a rewirable circuit safer if you were not allowed to add RCD protection?

Would you refuse to add a spur if you were not allowed to add RCD protection?

If you were asked to replace switches or socket fronts would you refuse if you were not allowed to add RCD protection?

Would other people here?

Of course, a DIYer can do anything he or she wants to do. Afterall, who would know?

A DIYer is still legally obliged to make reasonable provision for safety etc, which in practice means adhering to BS 7671.

But a professional electrician offering a professional level of service, such DIY thinking should never be a part of their function as a law-abiding, Regs-abiding, professional electrician.

It would be helpful if you could stop introducing imagined DIY thinking and concentrate on explaining, rationally, when, where and why the case exists for saying that existing components which you are not touching have to be updated to the current regulations....

It would also be helpful if you stopped assuming that I'm automatically going to disagree with you just because I'm asking questions.

 

[skenk]

Why was it locked?

My undertanding is a CU change means you take responsibility for all circuits

But do you? Or do you only take responsibility for the work that you do?

And what does "take responsibility" mean? To what extent can you take responsibility for the compliance of circuits you didn't install?

OK - you can check continuity and IR, and you can assume that nothing is so deep that RCDs aren't needed, if you believe that you need to in the first place, but you can't be sure there are no undersized sections, you can't be sure there aren't Band I and Band II circuits in the same enclosures, you can't be sure the cables are all in the correct zones and so on and so forth.

and as such they would need to be up to 17th standards.

So there are limits to what "responsibility" you can take - are there also factors which affect if you should?

For example - you say replacing the CU triggers responsibility, and thus, for example, RCDs.

What about replacing just a faulty MCB?

What if you had a rewirable CU with a circuit was on a fuse that was too big, and the customer was OK with you putting the right rewirable in, but wouldn't pay for CU replacement or an outboard RCD - would you refuse to do the work?

What about adding a spur? You could ensure compliance of your bit of cable by using conduit or BS8436 etc - do you think you have to bring the existing circuit up to 17th requirements?

Fair points

Yeah you have to make assumptions about cables in zones etc but you can look at the general condition of the installation/do a PIR and if alarm bells are ringing - integrity of terminations, grommits, sleeving etc - then refuse the work/recommend a re-wire. So yes to a certain extent you can only take responsibility for the work you've done but as far as you reasonably can then you should ensure all circuits connected to the new CU comply. The exception to this for me would be heights of switches and sockets which could remain as existing.

As for adding a spur, it's an addition to a circuit and I would do it only if the whole circuit complied with 17th - again, to the extent that that can be reasonably verified.

Replacing a faulty MCB is a repair rather than an alteration or addition, downrating a fuse is fixing a fault in my eyes although i'd recommend a plug-in MCB number.

Er, gulp, but I've not got the big red bookyet so unfortunately i can't look up the new reg numbers as yet

 

[ericmark]

Until yesterday I would have agreed with “sealeon” in that only way is with separate rcbo’s but reading this quarters “Wiring Matters” http://www2.theiet.org/Publish/Wire...8_autumn_wiring_matters__complete_adverts.pdf I am not longer sure. Page 24 shows section of new on site guide which seems to favour the 3 way split boards.
Also reading the Electrical Safety Councils advice on lighting with no earths http://www.esc.org.uk/pdfs/business-and-community/electrical-industry/BPG1_08.pdf they clearly seem to accept you may still allow the use of lights with no earths by using all class II equipment so can’t really see how in the light of that one can insist on lesser updates.
I do think we should try first to upgrade the lot but where we can’t then it seems we do have some leeway.
Guide 4 http://www.esc.org.uk/pdfs/business-and-community/electrical-industry/BPG4_08.pdf does say how you should work to current regulations. Some of the codes suggested are not what I would have expected. For example no RCD on a bedroom socket which has a shower cubical in I would have considered as Code 4 as it was allowed on previous editions of wiring regulations but the Electrical Safety Council say this is Code 1.
Until the 17th Edition a bedroom with a shower was not considered as a bathroom and we have not allowed sockets in bathrooms for many years. But when referring to previous editions of BS7671 we of course only go back to 16th Edition or BS 7671:1992 as before that date there was no British Standard it was only an IEE regulation which then must ask why we are allowed to refer back to 13th Edition and allow systems that complied with regulations in 1966.
I don’t know about the others out there but I was still at school and as a 15 year old was not really interested in wiring regulations at the time.
With all this in mind I have to agree with FingRinal and common sense is more important. One must bring the users attention to faults and I think the coding system is a great way to make it so the user understands how bad the installation is. But like with Part P which was altered to allow emergency work the same applies to the other regulations. Next someone will say we need to fit RCD’s to the buried 8 volt cables going to the door bell! It’s in the regulations! There is no exemption for extra low voltage cables buried in a wall but we all now even if we wanted we could not buy a RCD that would work on 8 volt.
Eric