EIC for submain db rewire

conrad · Mar 17, 2018

Part Rewire to do, small shop on a large premesis 4 lights, 2 sockets, 2 spurs...The existing DB(DB4) which is staying, is fed via 32A mcb from a sub main DB3. Fed by 63 A mcb in another DB2 which then goes to DB1 which is connected to origin. Took a while to chase through as all DBs are in seperate buildings. My question is how far would you go on the EIC in terms of inspect and test details of each protective devices and cable sizing in line etc as job will more difficult obviously access and isolating testibg at each point in 4 seprate buildings.

Strima · Mar 17, 2018

One schedule of inspections and test results stating which DB the DB you're working on is fed from with Zdb etc.

davesparks · Mar 17, 2018

How can you certify something as compliant when there is such an obvious discrimination issue?

The Ghost · Mar 17, 2018

davesparks said:
discrimination issue

Could you enlarge on that a bit please?

Toneyz · Mar 17, 2018

Are you saying DB 1 is the main DB this feeds DB2 which feeds DB 3 which feeds DB4 which you are wiring new circuits to?

Octopus · Mar 17, 2018

The EIC for the rewire of the submain needs to cover "both ends" of said submain.

Whats the zbd at the last CU?

conrad · Mar 17, 2018

3 phs Cutout. All brown singles 35mm ish main earth looks 10mm appears to be undersized for installation. Ze 0 24
MainDB at cutout in main building feeds
DB1 seperate building 40 meters away
feeds
DB2 in an external outbuilding
Feeds
DB3 another outbuilding. Zdb 0.70 TNCS.

Toneyz · Mar 17, 2018

So DB4 which you are installing new circuits to is fed from DB3 via 32A MCB. What is the Zdb at this DB?as max Zs for a C 32 MCB is 0.68! and that's the 100% figure.

Ian1981 · Mar 17, 2018

Sounds like submains fed from submains which is a discrimination nightmare

conrad · Mar 17, 2018

DB3 is the one im wiring new circuits from... so 0.70. Type 2 crabtree mcb 32A.

westward10 · Mar 17, 2018

What type of Crabtree mcb is it. I agree discrimination is to pot but sometimes you can only work with what you have. If main protective bonding is required at your premises is the cpc of the supply cable to DB4 of a suitable csa to support bonding. I would check the supply cable from DB3 to 4 is adequately sized and whether fault protection is maintained by the supply protective device at DB3.

conrad · Mar 17, 2018

But i havnt checked cable sizes at each point in line to DB3. Again being in different buildings its alot of work to actually do, before doing the job you are being paid to do. Eg if the db1 or db2 had an underated cable or any other issues then connecting anything after these wouldnt be acceptable.

conrad · Mar 17, 2018

By that logic you would also want those details from Main DB, DB1 and DB2 as theyre all inline.

westward10 · Mar 17, 2018

I would only confirm the size to DB4 from DB3 is adequate.

conrad · Mar 17, 2018

EIC for submain db rewire

conrad

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Strima

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davesparks

The Ghost

Toneyz

Octopus

conrad

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Toneyz

Ian1981

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conrad

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westward10

conrad

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conrad

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westward10

conrad

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