Filling in Cert for SubMain help?

[TPES]

Just a few questions on a test scenario, quite hard to explain in writing but hopefully you'll understand.


If a detached building is fed from an older type fuse with SWA, then the detached building is TT'd, (Earth Rod)

what details am i recording on the cert for....

Supply characteristics...
Would i tick TT on the cert as this is the newley installed earthing arrangment for distribution circuit to the garage im testing? or would it be the original Earthing arrangements back at Main CU?

Also maximum demand
PFC
Ze

Would this be taken from the sum main?

Ze for the new Distribution circuit at submain aswell as PFC and Max Demand..?


Characteristics of primary supply overcurrent protective device(s)

BSEN
Type
Current Rating
Short Cct Capicity

Is this the main fuse coming into the Main Dis board at the intake OR is it the fuse within the main CU that is feeding the distribution cct to the Submain?

I could work my way through the whole certificate..

an example of a cert filled in with a distribution cct from main CU, with TT at submain would make it alot clearer for me.

Schedule of test results...
For the SWA feeding submain. how would i get a Zs reading as the earth is not used from the SWA as i am using TT for the submain.

Soz if ive confused you..

 

[cornburn]

Why not do one cert for the swa and all the origin details like normal, then another cert for the TT installation, still with same origin details but both earthing arrangements ticked and your ze etc will be the TT readings?

I don't think there's a black and white answer for funny situations like this (or if there is I don't know it). If you asked 10 sparks to cert that installation I'd be surprised if you got 2 back identical, the red book just doesn't go into that much detail over cert filling in. Do whatever you think makes the most sense to get the information across to anyone reading it

 

[TPES]

May be this is why i have not had many replys.

So you think do 2 certs.

The situation does confuse be abit

 

[Graeme Harrold]

I would dothe main cert for the origin and supply CU detailing the swa circuit, then add another results sheet for the TT part as its a sub-board off of the main CU

 

[cornburn]

I would dothe main cert for the origin and supply CU detailing the swa circuit, then add another results sheet for the TT part as its a sub-board off of the main CU

The NIC forms have the right details on to use an additional sheet too, with zdb etc at the top. Not sure about other forms but the standard IET ones don't have anything that helpful on. As long as it's obvious to anyone else coming along afterwards surely that's what's most important.

 

[dichroic]

Just a few questions on a test scenario, quite hard to explain in writing but hopefully you'll understand.


If a detached building is fed from an older type fuse with SWA, then the detached building is TT'd, (Earth Rod)

what details am i recording on the cert for....

Supply characteristics...
Would i tick TT on the cert as this is the newley installed earthing arrangment for distribution circuit to the garage im testing? or would it be the original Earthing arrangements back at Main CU?

Also maximum demand
PFC
Ze

Would this be taken from the sum main?

Ze for the new Distribution circuit at submain aswell as PFC and Max Demand..?


Characteristics of primary supply overcurrent protective device(s)

BSEN
Type
Current Rating
Short Cct Capicity

Is this the main fuse coming into the Main Dis board at the intake OR is it the fuse within the main CU that is feeding the distribution cct to the Submain?

I could work my way through the whole certificate..

an example of a cert filled in with a distribution cct from main CU, with TT at submain would make it alot clearer for me.

Schedule of test results...
For the SWA feeding submain. how would i get a Zs reading as the earth is not used from the SWA as i am using TT for the submain.

Soz if ive confused you..

I am going to do my best to clarify this situation for you. Please forgive me if it ends up a little long winded.

By the way this situation is not "funny" or "complicated" at all once you fully understand it.

First of all there is only one ZE and that is at the source of the supply, ie where the electricity main fuse and meter is.

You treat the R1+R2 of your distribution cable (swa) like you would any other cable from the consumer unit.

On the schedule of test results it asks you for the type of earthing system. So if the property is on a TN-S system that is what you put on the first schedule of testing. On the second schedule for the garage you will identify it as TT.

You will have 2 schedules of test results. One for the main consumer unit and its outgoing circuits and one for your second consumer unit and its outgoing circuits.

Don't get confused by this situation. You will have one certificate as a standard installation but you will have TWO schedules of tests, one for each board.

I hope this helps.

Regards

Dichroic

 

[pevvers]

On the second schedule for the garage you will identify it as TT.

So where is the box of the schedule of test results to show that it is a TT?

Or is it just from the fact that the Zs, Zdb or Ze (depending on preference! ) on the 2nd schedule is going to be in the TT range?

 

[dichroic]

At the top of the schedule.

See Attached.

Regards

Dichroic

 

[pevvers]

Ah sorry, don't use IET generic forms!

 

[dichroic]

Ahh okay. Presumably you are using NICEIC forms?

They are slightly different so you will need to take your ZS reading at the main switch on your garage CU and note this under ZDB which is for the impedance at you distribution board or consumer unit. There is no provision on NICEIC forms for you to allocate the type of earthing system on the schedule.

So you will note the incoming earthing system on the part : Supply characteristics and earthing systems, and leave it at that.

Regards

Dichroic

 

[pevvers]

Yep, that's what I would do. Simple TN-S at the origin of the supply, and hopefully if someone is working on the TT part they should be knowledgeable enough to know that it is TT. If not, then I doubt they would be doing any testing otherwise!!

Mine wasn't the original post though, so I'm not sure what certificate model that the OP is using, it could very well be the IET standard ones, and therefore he will be able to mark the second sheet as TT.

 

[TPES]

It's the Elecsa EIC Certs, still not 100% on it