Todays 5 minute job

[mikel]

Small job for a builder to remove a built in double oven and fit new double oven. Shouldn't take long.

Well isolate circuit, remove existing oven from fitted . Inspect the wiring that was visible and all looks ok. Energise circuit for Quick Zs test before disconnecting existing oven 815 ohms

So isolate circuit and start investigate problem. Off with all electric and open comsumer unit to do r1+r2 test. No cpc for cooker circuit. Have to remove consumer unit to get to cooker circuit wire to find its wired in 2 core cable no cpc in it at all.

Further investigation under floors of house reveal that there is a seperate cpc for cooker circuit which some kind soul has cut whilst fitting gas central heating. Only way I can get a cpc to the cooker outlet is to join it too the existing one thats been cut. Took ages to sort out but at least now get a respectable Zs (0.39 ohms). 30 minute job ends up as a 8:30pm finish on a fridaybad day explode

 

[Evans Electric]

They always happen on Fridays . The worst thing is if my M8 is working with me and he will say words to the effect " This is going well , we'll be done by lunchtime and on our home"

Oh no we won't ...not once he's said that , everything will go wrong. :_|

 

[Megaohm7]

Small job for a builder to remove a built in double oven and fit new double oven. Shouldn't take long.Well isolate circuit, remove existing oven from fitted . Inspect the wiring that was visible and all looks ok. Energise circuit for Quick Zs test before disconnecting existing oven 815 ohms

So isolate circuit and start investigate problem. Off with all electric and open comsumer unit to do r1+r2 test. No cpc for cooker circuit. Have to remove consumer unit to get to cooker circuit wire to find its wired in 2 core cable no cpc in it at all.

Further investigation under floors of house reveal that there is a seperate cpc for cooker circuit which some kind soul has cut whilst fitting gas central heating. Only way I can get a cpc to the cooker outlet is to join it too the existing one thats been cut. Took ages to sort out but at least now get a respectable Zs (0.39 ohms). 30 minute job ends up as a 8:30pm finish on a fridaybad day explode

It's never a five minute job mate !! Good job you took a Zs reading though .

 

[batty]

Hope customer appreciates what you have done for them.

 

[revjames]

They always happen on Fridays . The worst thing is if my M8 is working with me and he will say words to the effect " This is going well , we'll be done by lunchtime and on our home" Oh no we won't ...not once he's said that , everything will go wrong. :_|

I'm telling Mr Smith about you.......

 

[bengie]

had similar myself the other day, changed a couple of damaged sockets and got a Zs of 2ohm so thought sod it, got to chase a loose connection now.

long story short tightened all loose connections and got the Zs down to 1.95ohm so tested Ze and that was 1.85ohm

turns out the lead sheath on the cable has broken down somewhere, calls the DNO who couldn't care less about that or the very old cutout so forced to convert it to TT. surprised that DNO didn't care.

 

[ianmacd]

had similar myself the other day, changed a couple of damaged sockets and got a Zs of 2ohm so thought sod it, got to chase a loose connection now.long story short tightened all loose connections and got the Zs down to 1.95ohm so tested Ze and that was 1.85ohm

turns out the lead sheath on the cable has broken down somewhere, calls the DNO who couldn't care less about that or the very old cutout so forced to convert it to TT. surprised that DNO didn't care.

This does concern me with DNO provided Earths which is why I still think supplying your own (by converting to TT) is safer from the point of view of consistency of earthing connection.

I guess before long Ze will be open circuit when rest of sheath splits fully.

 

[ProDave]

turns out the lead sheath on the cable has broken down somewhere, calls the DNO who couldn't care less about that or the very old cutout so forced to convert it to TT. surprised that DNO didn't care.

Was it the actual DNO that couldn't care less, or the customers Energy supplier.

I frequently find when the energy supplier is NOT the DNO, that the DNO won't take an interest and refer you to the energy supplier, and the energy supplier couldn't care less. The worst one I have encountered is N Power, who won't do anything to a telephone request, even saying it's dangerous and needs immediate attention just gets their standard "put your request in writing" response.

 

[batty]

This does concern me with DNO provided Earths which is why I still think supplying your own (by converting to TT) is safer from the point of view of consistency of earthing connection.I guess before long Ze will be open circuit when rest of sheath splits fully.

I would disagree with this I have found more faulty TT earths than any other earth and actually cannot think of any dangerous earth on tns or tn-c-s that I have come across. On commercial it would not be viable to TT system as you are going to then have to Rcd protect everything which is really not necessary. As said before if Dno provide earth I will always use it.

 

[Lurch]

Things can and will fail without maintenance. It doesn;t matter if the maintenance is down to the DNO or customer, a failed cable\joint etc... is still a failed cable\joint etc...

 

[sparkytim]

Have had several of these and my area DNO, EDF pretty quick to respond just phone Emergency supply fault number and report excessive Ze and they are duty bound to respond as they specify Max Ze of 0.8 on TNS AND 0.35 for PME (Oh Sorry Ian thats TNCS to us inside, Whats that Label say DNO sticks near cut-out when they connect our Earth into their Nuetral?)

 

[Lurch]

Whats that Label say DNO sticks near cut-out when they connect our Earth into their Nuetral?)

It would depend on whether it is a TN-C-S or PME system.

 

[sparkytim]

It would depend on whether it is a TN-C-S or PME system.

In 30+ years in this game i have only seen one

" PROTECTIVE MULTIPLE EARTHED INSTALLATION DO NOT INTERFERE WITH EARTH CONNECTIONS"

I think they mean the Bonding and MET connections indoors don't they ?

Unlikely for householder to dig up stakes down the road at the Multiple Earthing points.

So if they are happy to refer to TNCS installations as PME INSTALLATIONS why are some of us making a fuss about it?

PS

BRB PG 28 note definiton of PME and PAGE 33 Fig 2.4

TN-C-S system Note 3

"This type of distribution is known also as Protective Multiple Earthing"

 

[Andy™]

had similar myself the other day, changed a couple of damaged sockets and got a Zs of 2ohm so thought sod it, got to chase a loose connection now.long story short tightened all loose connections and got the Zs down to 1.95ohm so tested Ze and that was 1.85ohm

turns out the lead sheath on the cable has broken down somewhere, calls the DNO who couldn't care less about that or the very old cutout so forced to convert it to TT. surprised that DNO didn't care.

its upto the DNO to repair and maintain if they provided (ESQCR)

when you call, dont tell them its 1.85 ohms - tell them its O/C. gets their attention more

 

[Andy™]

TN-C-S system Note 3

"This type of distribution is known also as Protective Multiple Earthing"

TNCS is also (less) known as Combined Neutral & Earth (CNE), and is very different from PME (but rarely used for DNO distribution)

 

[Lurch]

In 30+ years in this game i have only seen one " PROTECTIVE MULTIPLE EARTHED INSTALLATION DO NOT INTERFERE WITH EARTH CONNECTIONS"

I think they mean the Bonding and MET connections indoors don't they ?

An attempt at humour? I'd have another read of the guide if I were you.

TBH, I don;t know why people are so against this fact.

PME and TN-C-S are not one and the same. FACT.

The regs say that TN-C-S is PME. Now the first half is FACT (that is, the regs say this line) but the statement is not correct.

Just because BS7671 says TN-C-S is PME doesn;t make it so. Argue it all you want, you can;t disprove actual facts.

 

[sparkytim]

Wet Fish

An attempt at humour? I'd have another read of the guide if I were you.TBH, I don;t know why people are so against this fact.

PME and TN-C-S are not one and the same. FACT.

The regs say that TN-C-S is PME. Now the first half is FACT (that is, the regs say this line) but the statement is not correct.

Just because BS7671 says TN-C-S is PME doesn;t make it so. Argue it all you want, you can;t disprove actual facts.

So perhaps You can enlighten us on Your understanding of the terms? ?:|

 

[sparkytim]

[quote name='Andy

 

[Lurch]

So perhaps You can enlighten us on Your understanding of the terms? ?:|

The answer is in the question. TN-C-S is just having the earth and neutral linked, PME is doing this multiple times. PME is generally delivered on a TN-C-S supply but a TN-C-S supply is not neccesarily always PME, although it probably will be.

 

[sparkytim]

The answer is in the question. TN-C-S is just having the earth and neutral linked, PME is doing this multiple times. PME is generally delivered on a TN-C-S supply but a TN-C-S supply is not neccesarily always PME, although it probably will be.

So how else can a TNCS be delivered then?