Filling out niceic form first time

[chrisgjudd]

Hi you guys have been really helpful. i am on my initial major with the niceic doing a consumer unit replacement on my father in laws house who is 86 years old.

The earthing arrangement is tt, i have put in a 17th edition contactum cu which means all is rcd protected the house being split up by the 2 rcds. certain features of the nic form baffle me i.e should i measure the electrode resistance or put lim, if i have to measure it what is the best way, i have a megger 1552. Also on the cut out is 1361 60/80a i take it it means it could have either fuse, how can a green horn such as i see which one.

cheers chrisgjudd:x

 

[steptoe]

cut out fuse,

NOT VERIFIED

you dont have the authority to cut the seal and confirm the size type or anything else to do with it. for all you know it could be a bit of 4mm copper across it!!!

as for the spike, its not really that simple to measure it if you dont have the right kit, there is a cheat way of doing it but although it will give the correct ans mr nic would deffo NOT be impressed if i told you how and he asked you to show him. :|

 

[kme]

If the MFT can take Ra reading, which (dim & distant memory says it can) ; surely he can do what would effectively be a Ze test to the rod to determine Ra? I`ve intentionally written this "as is" for obvious reasons; as I`m not mentally capable of laying out the H&S/EAWR side of it. (too much stella)

But I am right, aren`t I?

 

[norv]

In the Inspection, testing & certification book it shows 2 methods of testing Earth Electrode Resistance. Method 1 is using an earth electrode test instrument & method 2 is using an earth fault loop impedance test instrument, i.e doing a Ze measurement. They say this maybe used "as the approximate value of the resistance of the installation earth electrode"

 

[steptoe]

yes, it can be done using an MFT, but where are you going to find the voltage at to do it?

to test the spike you must remove the Earth conductor from the installation,

therefore you cannot turn on the power to the installation as you have now left it without an earth.!

CATCH 22

I actually do it this way usually, but I wouldnt be confident of Mr NIC approving of it,

ie, having the juice flowing with no Earthing conductor in place, never mind having it proved.

 

[M107]

Take the Ze reading as you normaly would & use that as the Ra, it is an acceptable method, used it myself on Wednesdays assessment with NICEIC.

As for the cutout, put down 1361 but in the current rating do as steptoe says enter "not verified".

 

[kme]

Steptoe:

If the installation is de-energised, with the earthing conductor removed from the MET (irrespective of earthing system), your voltage comes from incoming side of main isolator, surely???????

My NIC inspections have always gone ok using this method.......?

 

[steptoe]

Steptoe:If the installation is de-energised, with the earthing conductor removed from the MET (irrespective of earthing system), your voltage comes from incoming side of main isolator, surely???????

My NIC inspections have always gone ok using this method.......?

past lot of TT systems I have done have all had double pole isolators fitted as part of DNO equipment inside the meter box and been sealed.

are NIC OK with this method then?

want sure TBH, its not really an official method, is it???

I was always taught the 3 spike method, but to use this Ze way to get an average.

(ie, if I couldnt be ****d doing it correctly),



hey, we all learn something new here.

 

[Nicky Tesla]

Take the Ze reading as you normaly would & use that as the Ra, it is an acceptable method, used it myself on Wednesdays assessment with NICEIC.As for the cutout, put down 1361 but in the current rating do as steptoe says enter "not verified".

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But remember to leave the earth rod disconnected when you do or you will get a really good reading from the water mains and the gas supply pipework. And if the niceic notice you have an earth rod showing only 0.8ohms on your cert, they will know you have tested it wrong.

It says in the regs not to use supply pipes for earth rods, but if they are connected as they should be for main equi bonding, then if a fault occurs the vast majority of the fault current will go down the pipework, simply because a far lower Ze is at the pipework eg 0.8ohms compared to 100ohms at the rod.

 

[kme]

-----------------------------------------------------------------------------------------------------------------------------------But remember to leave the earth rod disconnected when you do or you will get a really good reading from the water mains and the gas supply pipework. And if the niceic notice you have an earth rod showing only 0.8ohms on your cert, they will know you have tested it wrong.

It says in the regs not to use supply pipes for earth rods, but if they are connected as they should be for main equi bonding, then if a fault occurs the vast majority of the fault current will go down the pipework, simply because a far lower Ze is at the pipework eg 0.8ohms compared to 100ohms at the rod.

Unless the supply pipe is alkathene. Which is one of the reasons the 17th production was altered from the "draft for public comment". The DPC stated that a water pipe COULD be used as a main earth. It was withdrawn after many of us pointed out that utility companies are increasingly supplying their service via alkathene.

Under which premise, the water bond could have a reading in the Kohms range (variant on the resistance of the water itself; which in turn varies relative to it`s hardness; and, to a point, it`s pressure).

No-one in their right minds is going to put a TT Ra down as <1 ohm. It simply wouldn`t make sense.

 

[M107]

Unless the supply pipe is alkathene. Which is one of the reasons the 17th production was altered from the "draft for public comment". The DPC stated that a water pipe COULD be used as a main earth. It was withdrawn after many of us pointed out that utility companies are increasingly supplying their service via alkathene.Under which premise, the water bond could have a reading in the Kohms range (variant on the resistance of the water itself; which in turn varies relative to it`s hardness; and, to a point, it`s pressure).

No-one in their right minds is going to put a TT Ra down as <1 ohm. It simply wouldn`t make sense.

Doesnt the 17th state that a water service pipe can be used as an earth...but has conditions attatched ? something to do with private water supply I think.

I've not got the book here so cant check.

 

[Mr Sworld]

Doesnt the 17th state that a water service pipe can be used as an earth...but has conditions attatched ? something to do with private water supply I think.I've not got the book here so cant check.

Lets quote the regs!

'542.2.4 A metallic pipe for gases or flamable liquids shall not be used as an earth electrode. The metallic pipe of a water utillity supply shall not be used as an earth electrode Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against it's removal and it has been considered for such use'

So I suppose a pipe from a private borehole could be used but it would of had to be designed to be used as an electrode when first installed.