hi,this is my first post.

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hi, first of all ill like to say thanks to this forum as i have learnt a hell of a lot by some of the posts.

my first question is on a niceic form under "maximum Zs permitted by bs7671" would you write the figure from the red book or the tabulated based on 80% of values ie for a 32a type b would you write 1.44ohms or 1.15ohms

next question what the best way to do a rcd test an rcbo on a light circuit, as testing at lighting point will expose live parts.

and finally if changing an unprotected mcb to an rcbo of same rating (say for a lighting circuit) would this be classed as a minor works?

thanks in advance

wayne

 
1.15 ohm

you can do the test on terminals or RCD if its easier. or wire a temp socket to circuit

EIC. your changing circuit protection.

and welcome to the madhouse. could this be another forum record between joining and first post?

 
hi, first of all ill like to say thanks to this forum as i have learnt a hell of a lot by some of the posts.my first question is on a niceic form under "maximum Zs permitted by bs7671" would you write the figure from the red book or the tabulated based on 80% of values ie for a 32a type b would you write 1.44ohms or 1.15ohms
Maximum PERMISSIBLE as per the big red book... pg 49 1.44ohms

If you have the NICEIC book, Inspection , Testing & Certification (Inc PIR's)

in Chapter 6 which refers to filling out the schedules,

Max Zs is clearly identified as the BS7671 values NOT the corrected 80% rule of thumb values!!

next question what the best way to do a rcd test an rcbo on a light circuit' date=' as testing at lighting point will expose live parts.

[/quote']

See page 91 of On-Site-Guide, 11.1 General test procedure RCD's

Tests made on Load side as near as practical to its point of installation.

Load supplied should be disconnected during the test.

so your light fittings 'SHOULD' be isolated & dead as you are testing at the RCD.

You need to verify that the RCD itself can meet required operating times at specified current....

without any leakage currents due to circuit characteristics having any affect!

and finally if changing an unprotected mcb to an rcbo of same rating (say for a lighting circuit) would this be classed as a minor works?

thanks in advance

wayne
Minor, Yes! ;)

EIC'S are 'New circuits & or Fuse boards',

amendments to existing circuit but NOT a new fuse board is a MWC!
 
hello and welcome to the forum.

Your questions have already been answered far to well by Special so I can not add to that.

 
Some rcbos use the circuit as part of its function. so they wont test without the circuit connected. When this is the case I use the lampholder test thing (cant remember the name soz) that I use fos Zs readings. Its a lot safer when doing things live.

 
i always test RCD's with loads connected where possible (unless it trips on half test, then test 1/2 in isolation). there are many things which could cause an RCD not to operate. testing RCD like that is the same as pouring water on a rod to get reading down. passes whilst your there, but not safe after you leave

 
Welcome wayne .

Max Zs data to be entered is full 100% figure , in your example 1.44 ohms NOT the 80% figure of 1.15 ohms.

Always Test RCBO [or RCD} at the consumer unit and OFF Load, you are testing the operating characteristics of the device,..... testing in circuit can introduce errors.

When changing fom an mcb to a RCBO you are changing the design of the circuit and unless you have documented evidence [ unlikely ] that the overload functional characteristics of the RCBO are identical to those of the mcb being swapped, then it has to be an E.I.C.

 
Welcome wayne .When changing fom an mcb to a RCBO you are changing the design of the circuit and unless you have documented evidence [ unlikely ] that the overload functional characteristics of the RCBO are identical to those of the mcb being swapped, then it has to be an E.I.C.
??

No need for an EIC IMHO! :| :(

Any alteration to a circuit, (e.g. adding an additional accessory), changes the design of a circuit.

But it is ONLY necessary to issue an EIC if you have ADDED A new circuit, or replaced the CU.

For an alteration to a single circuit a MWC is perfectly acceptable. Reg 631.3 page 163.

MWC includes spaces for:-

  • Description of works / address / date
  • Earthing arrangement TN-C-S/TN-S/TT
  • Method of fault protection
  • Protective device TYPE & RATING
  • Earth continuity.
  • Insulation Resistance L/N, L/E, N/E
  • Earth fault loop impedance
  • Polarity
  • RCD operation times
  • Comments & Departures from BS7671.
  • Authorised signature & declaration.

Also included on the NICEIC MWC are:-

  • R1+R2
  • Max disconnection time & Max permitted Zs
  • Wiring system type
  • Installation Method
  • CSA of conductors & CPC

The only extra stuff you would get with an EIC would be :-

  • Equipotential bonding conductor materials & sizes
  • Means of Earthing .. Supplier or Rods (& Locations of earth rod)
  • Supply characteristics Voltage / Frequency / PFC / Ext loop Imp (Ze)
  • Number of live conductors single or three phase, AC / DC
  • Main switch; No of poles / Volt & Current Rating / Location
  • Main supply protective device, Rating & Type
  • Max demand.
  • Short cct capacity of protective device
  • Schedule of Inspections tick boxes.

of which.....

None will have been changed by an MCB-RCBO replacement.?

Obviously an EIC will cover everything, but other than wasting a lot more paper a MWC is perfectly adequate.

If changing two or more circuit characteristics then a EIC would be better than multiple MWC's! :) ;)

 
thanks special location, you have made my mind up about using mwc instead of eic, i was slightly unsure as there seems to be different opinions which certs to use. also had a couple of different replies to what the value of zs is to be entered in cert but was almost certain that it had to be the red book value just wanted to double check. thanks again to all, its interesting getting different replies.

 
None will have been changed by an MCB-RCBO replacement.?

Obviously an EIC will cover everything, but other than wasting a lot more paper a MWC is perfectly adequate.

If changing two or more circuit characteristics then a EIC would be better than multiple MWC's! :) ;)
I would disagree with that, Specs as the "extra stuff" is important especially if you have not installed the original MCB anyway. You need to check all of that anyway before starting the job (bonding, earthing etc...) so why not document it in an EIC (albeit with a single line on the schedule of tests page)? That way, if there is an issue in the future, you can prove you have performed the necessary tests/checks.

This is just my opinion/preference as both viewpoints would seem to be equally valid in BRB land.

Ian.

 
I would disagree with that, Specs as the "extra stuff" is important especially if you have not installed the original MCB anyway. You need to check all of that anyway before starting the job (bonding, earthing etc...) so why not document it in an EIC (albeit with a single line on the schedule of tests page)? That way, if there is an issue in the future, you can prove you have performed the necessary tests/checks.This is just my opinion/preference as both viewpoints would seem to be equally valid in BRB land.

Ian.
Agreed BRB is very much open to interpretation...

but I would say..

"if you have not installed the original MCB anyway"

by that argument every job you go to where you haven't previously installed the CU you must do an EIC for EVERYTHING!!! :_|

e.g. just adding an additional socket or light position onto an existing circuit.

you have not installed the original MCB. The circuit is now longer.

Overall load and max demand would have increased.

so now becomes EIC!! :( :| where would you use a MWC??? ?:|

Whereas the original question was... changing an MCB to RCBO of the same rating?

i.e. 6A type B MCB for 6A type B RCBO...

all Zs limits would be the same...

and the only difference we are adding is an RCD element into the circuit.

or are we suggesting replacing a faulty 6A MCB for another 6A MCB also an EIC?

Or

adding an in-line 30ma RCD onto a lighting circuit, leaving MCB the same is also an EIC?

In the original question the CU for the installation would have had "X" number of circuits...

after the MCB-RCBO change the CU would still have "X" number of circuits, (NOT "X"+1 circuits).

So NO additional circuits added (which definitely IS an EIC), so MWC perfectly adequate....

If you do want to test and document extra stuff.. you can always write it in the comments box...

But no need to waste 3 extra sheets of paper though! :|

90%+ of the "Extra Stuff" relates to the supply charactersitic... which HAVE NOT CHANGED...

ie. No new tails/main switch/bonding/supply voltage-phases-conductors/Main cut out fuse etc.. etc...

Yet from our MWC tests we will know that the

polarity/earth continuity/Zs/Ins Res/RCD times/Cable type conductor sizes etc.. re the amended circuit are all adequate...

so what safety risks are left open?

?:| :|

 
Like for like MCB swap (6A wylex for 6A wylex for example) then yes a MWC but you are not just modifying an existing circuit by not putting an identical device back in you are potentially changing the characteristics of that circuit. For this reason, I have done EIC's in the past, but I do see where you are coming from and may defer what I do next time until I am in that position again.

I guess the argument really comes down to "is it provisioning of a new circuit"? I can see reasons on both sides of this and, as usual, the BRB is far too vague in this.

If the bonding cables are not up to spec (or missing) then that needs fixing even before you start any other work but thats true of any work but my MWC I use have a checkbox for that anyway.

I think the bottom line here (as we are just discussing semantics now) is either would seem to be acceptable and the OP should do whichever he is comfortable with.

Ian.

 
i can see that this is basically the preference of who ever does the work. and i think ill prefer to use mwc for this as on niceic paper work there is all the info i think is needed, but would still check bonding and ze ect. but have just been looking thru the nic eic inspection, testing and certification book and on pg 80 theres a table which under ref H i read it as its not acceptable to use mwc, would this mean that niceic would not except mwc for replacing mcb to rcbo?

 
I think I have that book at home somewhere but if thats what it says then possibly. If you are NICEIC then call them and ask their advice.

Ian.

 
im not with nic eic yet but am planning to go with them in a few weeks so have been using there green forms to familiarise myself with them.

 
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