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CU replacement
RCW
6 Posts
Question
What testing should be undertaken when replacing a CU?
Should the property have a EICR before the replacement is carried out?
 
11 Replies
mapj1
2170 Posts
Legal minimum, on completion, before energisation, it should be checked to be safe .

To BS7671, expect a set of tests results for each circuit for IR and either R1+R2 dead test, or maybe the Zs before it was turned off, and some notes about wire sizes suitable for the breaker that protects them.

It is not a regs requirement, but in reality to do some sort of check before removing the old one is a very good idea, as it saves time afterwards trying to fault find with the power off. Especially true if RCD protection is being extended to circuits that did not have it before, as there is a tendency for this to reveal hitherto unknown issues that mean with the new board you cannot get the RCD to stay on. Typically it all works just fine until it fires off at 5 o'clock on a Friday, or after lunch on Saturdays, just after you have put all the tools back downstairs in the truck.
Farmboy
192 Posts
Have a look at Best Practice Guide 1 by Electrical Safety 1st, it's all in there with handy flow charts at the back:
https://www.electricalsafetyfirst.org.uk/professional-resources/best-practice-guides/

Also see guide No 4 re EICRs.

F
Chris Pearson
1531 Posts
This begs the question, "why do you want to change the CU? Surely it must be on the recommendation of an EICR.
Farmboy
192 Posts
Chris Pearson:
This begs the question, "why do you want to change the CU? Surely it must be on the recommendation of an EICR.

Consider a homeowner who looks at their rewireable fuse board and wants a consumer unit, with CBs, just like they've seen elsewhere , so they don't have to fiddle with bits of fusewire - and don't know anything about eicrs.

ebee
721 Posts
I always insist on doing an EICR prior to CU change. It`s only fair both to me and the customer
Chris Pearson
1531 Posts
Farmboy:
Chris Pearson:
This begs the question, "why do you want to change the CU? Surely it must be on the recommendation of an EICR.

Consider a homeowner who looks at their rewireable fuse board and wants a consumer unit, with CBs, just like they've seen elsewhere , so they don't have to fiddle with bits of fusewire - and don't know anything about eicrs.

If it's that ancient, is the rest of the installation likely to be satisfactory? Best to know in advance if a complete rewire is required!

RCW
6 Posts
The current consumer unit is not that old, the property was rewired in 2003

The reason for change is damage to the CU plastic case  (it’s the older split type with one RCD) plus the meter tails are 16mm T+E   
Chris Pearson
1531 Posts
Well then, an EICR is overdue. Much of the inspection and testing will have to be done in the course of installing the new CU, but most of it doesn't have to be done twice. If you have the EIC for the re-wire, so much the better.
Alcomax
194 Posts
ebee:
I always insist on doing an EICR prior to CU change. It`s only fair both to me and the customer

Exactly as ebee says.  An EICR is a snapshot in time. The greater the period elapsed the chance that something has changed increases. If for example, it is a "distress change", then perhaps go ahead and inspect/ test as is needed, but for your own protection do a Report first. Things that are a deal breaker you do not want to deal with once you have ripped the old one out. You are then at the point of no return.

Perception is everything in contracting and whispers become "fact. Many customers view a Consumer Unit change as a cure for all ills, many then presume the whole install is "new" and all sins have been "absolved". At the end of the day the same erroneous perception can be derived by simply replacing all the accessories for new ones........builder stylee. The murky part of the electrical industry uses a new CU as a whitewash for a badger install, very much the case in rental for example.

UKPN
127 Posts
"whitewash for a badger install" In 2020? surely not!

Regards. UKPN⚡
ebee
721 Posts
I once got asked by another trade "X has been charged £xxx just for a new consumer unit, is that expensive" my answer was "well if that is actually all that has been done then yes it could be, but if anything like a proper decent inspection and perhaps a few corrections along the way has been done, as in my opinion it should be, then it could well be a very reasonable price"

You would not expect your motor mechanic to fit new brake linings if your wheel is hanging off without a "lets fix this wheel first then we will do the linings" comment would you?

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