How many times to test?

[Rockingit]

I've a new build in it's death throws of 2nd fix and it's testing time, but there's an interesting twist: The DNO are due to replace the supply transformer, and have to, for various reasons I won't bore you with as on other threads already. So by my reckoning there's diddly point in doing any of the live tests until that's done as the characteristics and therefore results will be completely different.

But obviously the place needs energising so do I do the entire thing twice or just split it into two shifts and do the live tests afterwards? Obviously, I'll satisfy myself that the place is safe to be left and will have done SOME live tests, just not necesssarily all of them and all the paperwork. There's a total of FIVE DB's and sub mains so it's quite a lot of testing needs doing.

Thoughts?

 

[mickys86]

I would probably do the dead tests, RCD test pefc pscc and ze now. Your only really missing out Zs But the other tests don't take that much time and I'd rather know it was done properly

 

[johnboy6083]

I would fully test the sytem first, and then use your R1+ R2 when its renergised after the change over. Obviously Zs at each DB for cascading reasons. You know the max Ze they are required to adhere to for supply type, so you can use that to leave the system energised.

 

[Rockingit]

I would fully test the sytem first, and then use your R1+ R2 when its renergised after the change over. Obviously Zs at each DB for cascading reasons. You know the max Ze they are required to adhere to for supply type, so you can use that to leave the system energised.

I did think of just using the meaured R1R2 and doing the maths, but the Zs figures will be different again due to a host of other earthing paths. I'm expecting to see Zs/Zdb figures way below the Ze on account of having supplementary bonding to about 50m2 of steel plate buried 4m deep in the foundations!

Do RCD trip times vary dependant on supply voltage? Never really thought about it!

 

[johnboy6083]

Your Zs will only ever be lower than the calculated method. The only thing that can get worse is PFC, Ze and polarity can be reversed

 

[needasparks]

Just a question, what would you do if they changed the transformer a month after you have finished. would you go back ?

 

[Spazz]

How would you know if they changed the transformer? I doubt they will inform you.

You issued an EICR on the completion of the work to state it was in good/safe working order when you installed it (like you MOTed the Installation)

If you go back a few days later to a few months/years later its a PIR am I not wrong?

If the client wants a PIR then they have to pay for it


If the DNO change anything dont they have to make sure its safe when leaving - they are not hardly going to leave a supply of 500v going down the 240v side - and if they did it wont be your fault it would be theirs!

Same as if the earth value was to high - their fault not yours!

 

[trev]

You're issuing your cert and schedules as at the day you carried them out mate. imho it matters not a jot that the DNO are changing things at some point in the future, like needasparks says what if they changed the transformer/supply cable/earthing system a month or even a year after you did your testing?
In your position I'd get it done, out of the way and billed

 

[Rockingit]

The reason that the transformer is being changed as the DNO have required it in order to satisfy the demand for the property as there's a ground source heat pump and various other bits been installed. I can't actually energise the entire installation anyway until it's done otherwise there will be fat fuses popping, but the DNO are on a 6-8 week lead time to do the work and it's due for handover by the end of the month. Don't ask how it's gotten into this bun-fight but it's not MY doing!!

I think what I'll do is energise what's needed for now, and do the full tests as it is today and issue the EIC as a new. When the thing eventually gets swapped over and the rest can get turned on then I'll go back and do everything again, issue a replacement EIC as a modification. As you say, the dead tests won't have changed in a few weeks so that's a copy and paste job.

Test the same job twice? Double bubble.

 

[Rockingit]

How would you know if they changed the transformer? I doubt they will inform you.

You issued an EICR on the completion of the work to state it was in good/safe working order when you installed it (like you MOTed the Installation)

As per above ^^^, the issue is that the changeover is REQUIRED in order to sign the place off. It should have been done months ago but has been delayed due to politics, and it's ME that's placed the order on behalf of the client, so yes, I'll know straight away. It's costing the client £4.5k to have 'their' pole upgraded.

 

[Deleted member 26818]

To be honest, the only live tests that you are required to record are those at the origin of the installation (Ze, PFC and RCD).
You don't have to record both Zs and R1+R2 on the schedule of test results.
I wouldn't have thought it would be too dificult to just print out a new front page when the Transformer is changed.

 

[Rockingit]

To be honest, the only live tests that you are required to record are those at the origin of the installation (Ze, PFC and RCD).
You don't have to record both Zs and R1+R2 on the schedule of test results.

Haven't got the book with me at the moment, but I'd always thought that you did simply as it's on the model form? I'm all for trying to find some short cuts on this job!!

 

[Deleted member 26818]

Yes, sorry, getting mixed up with PIRs, you do need to record the value of Zs for an EIC.
However, as you are most likely aware, Zs can be calculated, by adding the declared value of Ze to R1+R2.
I believe the OSG states that use of the value declared by the DNO is the prefered method?

 

[johnboy6083]

what spins says regarding using declared values is good if you have used the standard circuits in the OSG, which use declared values of Ze as a starting point. If you have carried out the design yourslef, and have any circuit which has a Zs aproaching maximum, then yoyu will have to manuallycheck that each one will still comply. In practice i know that the Ze will probably stay the same, or decrease, but its your name on the ticket.