Testing & Recording Results Of Sub Mains

[TPES]

Just after some help on recording the results really. I suppose it will be the same for a single phase sub main in domestic premises as it would be in a factory with a number of 3 phase sub mains. Im guessing..

If your adding circuits to a submain what exact parts do you test and how do you record the results on test sheets?

Do you treat the sub main just as you would the Primary CU and do all your readings from that one Unit or do you do tests from the supply cable coming into the submain?

What details are filled in under "supply characteristics" is it the supply directly feeding circuits from submain, or is it the main supply in the primary CU that feeds the submain.



What is the correct way to record your results.. An example of a test sheet would be appreciated, just to see how its laid out.

 

[Des 56]

I measure the Z DB from the sub main
Although there could be parallel paths it is not always possible to record ZE
There is facility on most certificates to record that the dist board is not at the origin of the installation and space for the results of the sub main are provided there

 

[Mr Mark Sparks]

this is an ongoing issue the ze and origin details should be taken at the meter possition but this is often not easy so either treat your local cu and submain as the "installation" or record what you can and note lim on the cirt for areas not tested........never take a guess

 

[chocolate]

Technically, your test certificate should include all information from the the point the supply enters the building up to and including whatever work you did.

So if you add a new supply for DB3 which is to be fed from DB1, which in term is fed from DB MAIN ( where the intake position is ), your supply characteristics relate to DB MAIN. Your 1st shedule of inspections/test results for the circuit feeding DB1. Then a 2nd schedule of inspections/test results for your new supply from DB1 to your newly installed DB3. On the 2nd schedule of test results, your Ze ( which many prefer to call Zdb, as it isn't at the source of the installation ) is what you measure at the supply side of the main switch for DB1 when it is switched off.

Sounds crazy ?????

But ( as per regs ), that's what is expected to produce a full certificate.

 

[ryanryan]

as we are on the topic of industrial supplies..

installing a new DB..

from a 11kv ring..

to sub station C for example..

supplying a 800a sub supply to to panel C 2..

suppling panel board C2/3...

i would like to suplly a 100a 3PN DB>>>>>

Am i responsible for all of the Pre DB install?

 

[chocolate]

I would say you are responsible for whatever circuit you install, to ensure safety, upto the main intake position for that industrial site - where the main earthing conductor is.

If you install a DB anywhere, you are saying that you are happy with the earthing / bonding / loading , etc.

 

[micspark]

Good day Gents

I find this subject frustrating as I am testing a sub DB which is a new installtion,it is the 6th sub DB in the network of DB's which starts at a 800A supply.What do I put for my supply characteristics?Is it the 800A details at the source of the network or the supply details of the breaker feeding my new board?Help or examples of test and inpection certificates would be much appreciated as I am getting so many different answers.

 

[rich.250]

Yes supply characteristics is the DNO's fuses.
As said before I would have a schedule of results for each DB upto where you are.
Although I'd only test the sub feeding what your doing. I wouldn't test all circuits.

 

[malcolmsanford]

I think the new SoTR form as made this much clearer to be honest.

If your using the generic type based on the ones in the BGB then it states Zs at DB so your pretty much there with that one.

I normally do the tests for the sub main on one line and then if there is any final circuits also involved leave a few spaces and put them on the SoTR as well.

As for the EIC well in your case it would be virtually impossible to do a Ze at origin I would imagine, If there is by chance an existing result, then you could measure one if possible and compare, though of course you would have parallel paths, which would affect the result. But at least you proved there was a path.

You could just put by inquiry, which would be for instance a TNC-S @ 0.35ohms, personally I would only do this if it was unsafe to take a Ze reading at the time.

You could wait until there may actually be a time when you can isolate the whole installation and do a correct reading, but that is highly unlikely in large complexes.

If you do either of the first 2 then you need to highlight this on the EIC under comments on the existing installation

As for supply characteristics and earthing arrangements that should IMO be at the origin of the installation(s)

 

[micspark]

Thanks fo the useful information,so you say I would have test results fo all boards and only test the circuit feeding my new db?Would I just attain the results off the existing test sheets for the other boards?

Regards Mike

 

[micspark]

The way I would sum up my understanding is that I would use the supply characteristics of the DNO,test the new cable feeding the new installation having one SOI and two SOT's. Thanks for the help forgive my questions I am just trying to get it 100% correct first time.

 

[malcolmsanford]

You only test the work you have done.

If your running in a new 25mm SWA sub main for a new DB then that is what you test on the SoTR the sub main. You take your Zs @ DB Ipf @ DB polarity and phase rotation (if required)
and then you do your testing on the circuit R1+R2 or R2, IR, polarity Zs etc etc.

On your EIC you need to then complete the certificate as it asks.