What exactly can an 'domestic installer' do?

[ianmacd]

to be honest I'm stumped 10ohm difference ...but on a tn c s all controlled by the DNO so go on give us a clue ?????

about? As Green Hornet said, contact DNO.

 

[steptoe]

Does that mean Im right Mr Steptoe ? ?:|

can you verify the safety of the installation?

all the tables given in BS7671 are now invalid as they are based on pme max of 0.35 ohm , so you must note in deviations box this fact and whatever other method you have used to ensure disconnection times are met.

 

[sarni31]

about? As Green Hornet said, contact DNO.

About the correct answer for this question.....Guiness Drink

 

[Lee321]

did Dan get the point about we are only concerned with the installation after the stop the cock?

touching back on the domestic diy stealing our work its no better on the big commercial side.

modular wiring systems were the fuse boards come with sockets on the top for all the final circuits and then prewired and connected adaptaflex with matching plugs just plug in then go to the various pou.

its actually possible for multi million pound contracts not to have any connecting up on site at all bar sub mains

needless to say all the big firms baileys and the likes using unskilled labour to pull all these "metal tubes" in on basket which was installed by mechanical spanner operatives not needing any electricians at all. Guiness Drink:z

 

[dan.]

yeah i get it. The time served spark still didnt bond to the copper part. My point is still valid just because you are time served doesnt mean you always do things properly.i know what ive seen.

 

[Andy™]

sorry GH, but I think that is wrong,that is what all the calcs given in 7671 are based on,

but I think its down to the DNO to verify what they will actually give you.

I have found that in most cases they will simply disconnect and tell you they are no longer supplying the earth if it is too high.

if an earth is provided, it must be maintained.

But if it is a DIY PME, when it should be TT, then they could disconnect and leave it TT

 

[green-hornet]

One of the first things I do when quoting for a rewire is a Ze test, this I do on the first visit.

I did a rewire last year on a very large house, the house next door had had a rewire a year earlier.

When I tested the pme I found a Ze of 0.57, I asked if I could test the next door and found they had a reading of 0.58.

The electrical installation cert for that property had a reading of 0.35 for the actual reading of Ze.

I contacted the dno, who came out twice to survey the problem, eventually they sent a field team out and found a fault on one of the overhead cables.

After the fault had been rectified the Ze readings on both houses droped to 0.12

Another case I had was a pme reading of 0.39 slightly over the max permitted of 0.35,

again I contacted the dno who said they would monitor the situation but would not take any further action at this time.

I noted the deviation on my EIC with a note detailing the conversation I had with the dno.

If a repair can not be made the dno will disconnect the tail from nuetral and remove there obligation to supply an earth leaving the electrician liable to install the correct earthing requirements.

Its better to find out before you start a rewire than after.

 

[jl-heating]

One of the first things I do when quoting for a rewire is a Ze test, this I do on the first visit.I did a rewire last year on a very large house, the house next door had had a rewire a year earlier.

When I tested the pme I found a Ze of 0.57, I asked if I could test the next door and found they had a reading of 0.58.

The electrical installation cert for that property had a reading of 0.35 for the actual reading of Ze.

I contacted the dno, who came out twice to survey the problem, eventually they sent a field team out and found a fault on one of the overhead cables.

After the fault had been rectified the Ze readings on both houses droped to 0.12

Another case I had was a pme reading of 0.39 slightly over the max permitted of 0.35,

again I contacted the dno who said they would monitor the situation but would not take any further action at this time.

I noted the deviation on my EIC with a note detailing the conversation I had with the dno.

If a repair can not be made the dno will disconnect the tail from nuetral and remove there obligation to supply an earth leaving the electrician liable to install the correct earthing requirements.

Its better to find out before you start a rewire than after.

this is the very reason i come on here the advise is excellent. you dont learn this stuff on site.. keep up the good work guys..

the wife just says that i am sad, i just packed my onsite guide and some other stuff to read while on holiday lol....

 

[Doc Hudson]

this is the very reason i come on here the advise is excellent. you dont learn this stuff on site.. keep up the good work guys..the wife just says that i am sad, i just packed my onsite guide and some other stuff to read while on holiday lol....

I do like to hear that members find the advice on the forum to be good. Not sure taking your technical books on holidays is required though, maybe a bit of lighter reading more appropriate JL?

Doc H.

 

[Doc Hudson]

but ive already stated that the house is piped in copper . Yet it still wasnt bonded. Ah balls to it i give up. You experienced sparks obviously aint gonna listen to a lowly DI.

I think there are many "lowly DI's" on the forum, who's input is very valuable and listened to by others. Your input is also important Dan.

Doc H.

 

[steptoe]

if an earth is provided, it must be maintained. But if it is a DIY PME, when it should be TT, then they could disconnect and leave it TT

ok folks, Im getting a little mixed up now, so I apologise in advance as to if I have it wrong.

you are saying that DNO must ensure the earth is within the limits stated in 7671, (although DNO does not work to this reg) and if not then they must improve it.!?

GH reckons they will try but if it proves too much hassle then simply disconnect and you provide your own earth.

I tend to agree with GH as I was always taught DNO gave you an earth out of convenience, NOT obligation.

 

[steptoe]

i know the regs are for guidence and own judgement should be used in some installtions but i ive seen sparks doin some real dodgy stuff.no bonding on lead mains water and gas pipes in an old terrance with copper throughout is askin for trouble in my book.im not tryin to start an argument just pointing out that there are bad sparks which ever route they took to become one.

dans words not mine,

as I have said before, why would the pipework before the stoptap or meter be of any relevance to a spark, you stated lead pipework, you can not LEGALLY bond lead pipework.

before you start to argue please make sure you post correct information, remember,

the old spark you are ****ging off may have been me or Deke. (ha ha Deke)

 

[Andy™]

From ESQCR

Equipment on a consumer's premises24. - (1) A distributor or meter operator shall ensure that each item of his equipment which is on a consumer's premises but which is not under the control of the consumer (whether forming part of the consumer's installation or not) is -

(a) suitable for its purpose;

(B) installed and, so far as is reasonably practicable, maintained so as to prevent danger ; and

© protected by a suitable fusible cut-out or circuit breaker which is situated as close as is reasonably practicable to the supply terminals.

simply changing it from TN to TT isnt always an option. Incase of high reading on TNS or PME, then its usually a joint on their underground network thats failed. it will effect other properties and possible for the joint to completely fail, so will need rectified.

they cant exactly go round and knock on a few doors and say 'we have a problem with out wiring, you will need to call a spark and get him to change your earthing to TT'

full text of ESQCR is here

 

[steptoe]

From ESQCRsimply changing it from TN to TT isnt always an option. Incase of high reading on TNS or PME, then its usually a joint on their underground network thats failed. it will effect other properties and possible for the joint to completely fail, so will need rectified.

they cant exactly go round and knock on a few doors and say 'we have a probTTlem with out wiring, you will need to call a spark and get him to change your earthing to '

full text of ESQCR is here

ha ha,

yes I get your point, apologises,(thats not spelt right)

but perhaps at same time its also a case of they are not obliged either?

it does seem a grey area.

thanks for the info mind. good to know.

by the way, I have no idea how I moved the TT into the middle of problem so I cant move it back.!

 

[Andy™]

ha ha,yes I get your point, apologises,(thats not spelt right)

but perhaps at same time its also a case of they are not obliged either?

it does seem a grey area.

thanks for the info mind. good to know.

by the way, I have no idea how I moved the into the middle of probTTlem so I cant move it back.!

they are obliged to give PME for new supplies (reg 24- (4))

for existing, if they have provided it at some point in the past, it must have been safe, and so should be maintained at all times

and for the moving on TT, if you click to edit your post, you can alter the text in my quote, like i did in your quote there

 

[batty]

surely with pme or any other system it will depend how near you are to the transformer as to what loop you get. Sometimes they may not be able to give you a pme supply if loop is over .35ohms. I understand about bad joints but that may not be why loop is so high.

Batty

 

[batty]

they are obliged to give PME for new supplies (reg 24- (4))for existing, if they have provided it at some point in the past, it must have been safe, and so should be maintained at all times

and for the moving on TT, if you click to edit your post, you can alter the text in my quote, like i did in your quote there

Not on farm installs or caravan parks and a few others.

 

[Andy™]

surely with pme or any other system it will depend how near you are to the transformer as to what loop you get. Sometimes they may not be able to give you a pme supply if loop is over .35ohms. I understand about bad joints but that may not be why loop is so high.Batty

but if they are so far away from Tx that loop is over 0.35, then your probably gonna have problems with VD, and possibly Zs (and maybe even phase/neutral loop so dead short wont trip breaker in time)

 

[Andy™]

Not on farm installs or caravan parks and a few others.

it says

(4) Unless he can reasonably conclude that it is inappropriate for reasons of safety, a distributor shall, when providing a new connection at low voltage, make available his supply neutral conductor or, if appropriate, the protective conductor of his network for connection to the protective conductor of the consumer's installation.

but it also says elsewhere that PME cannot be used in certain conditions (like the caravans you mentioned), but incoming supply to site can be PME and so can certain buildings

 

[steptoe]

but if they are so far away from Tx that loop is over 0.35, then your probably gonna have problems with VD, and possibly Zs (and maybe even phase/neutral loop so dead short wont trip breaker in time)

that shouldnt be an issue, after all on TNS its 0.8,

or on TT it can be a LOT LOT more, its about how you can also prove compliance outside 7671,

I have often had TNCS >0.35 and simply noted on my cert and used some other means of proving disconnection times.