Jump to content

DONT STAY LURKING AS A GUEST,

JOIN TEF AND BENEFIT FROM MEMBERSHIP:

CLICK HERE TO JOIN.
  •  
     
     
Countdown To Christmas!
 

 
  • 0

hi,this is my first post.


monkey5

Question

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

Link to comment
Share on other sites
 

Recommended Posts

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.

Link to comment
Share on other sites
 
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.

The ones with no Logo I hope :o

Link to comment
Share on other sites
 
Andy™

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

Link to comment
Share on other sites
 
SPECIAL LOCATION

Yes as ian says, the BRB is very much open to interpretation...:|

And at the end of the day, it is the person who is doing the work who will have to make the final decisions.

Proving that ALL essential safety checks have been done and to ensure the safety of any alterations.

IMHO its about being able to justify your choice of documentation.

This is where it is good to be able to debate the various pro's & con's and interpretations with other qualified & competent persons, on forums such as this!:D Applaud Smiley (without having any hissy fit scraps!!! :):^OGuiness Drink)

I guess the bottom line has to be.. "If you are in any doubt do a full EIC!" your bottom end is well and truly covered then.

Also the table the NIC book has an element of interpretation..

Item 'H' refers to replacing items of switchgear on a 'NON like for like basis'..

I tend to read this as if you are upgrading the fuse rating or changing the characteristics (re Zs!)..

such as wired 30A to 32A MCB, wired 15A to 16A MCB etc..

or upgrading light circuit from 6A to 10A maybe?

I understand 'like-for-like' to mean an item with equivalent ratings / capacities,

NOT just a direct identical manufactures make - model etc..

e.g. Like 4 Like?

A Gainsborough 8.0K shower replaced with a Triton 8.0k shower is 'like 4 like', but NOT if replaced with a 9.0k shower?

A 20A 3036 replaced with a 20A 60898 is NOT 'like 4 like' as although they have identical current ratings,

they have different max Zs values in the tables on pages 48/49 of BRB..

But when swapping a 6A type B MCB BSEN60898

and a combined RCBO with 6A type B BSEN61009-1, overload protection.

Both have the same max Zs, (7.67ohm), from the table on page 49.

the time current characteristics ref with reference to PFC are on the same graph... PAGE 249.

So to my interpretation the overload protection & disconnection time characteristics are 'Like-4-Like',

all we have done is just added shock protection as well???

If I had fitted a standalone RCD next the CU and diverted the circuit through that I would also have just done a MWC.

As said the NIC guidance is just as much open to interpretation as the BRB?

you just need to be able to justify your case and reasoning.

:|:)

Link to comment
Share on other sites
 
SPECIAL LOCATION
The ones with no Logo I hope :o

phttt! :_|

The "green forms" are none logo'ed!

Logo'ed ones are pretty colours... reds & purples....:DBlushing

:|

Link to comment
Share on other sites
 
SPECIAL LOCATION
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.

Thats good...

you can use them to show the inspector how you would fill out the documentation...

and it would add the extra bit of boot-licking grovel factor to be using NIC green forms rater than just a-n-other free download forms!:D:)

Link to comment
Share on other sites
 

i would like to use minor work but in the nic eic hand book it states

replacement of individual item of switchgear inc control switch or protective device not in like for like manner eg replacement device has diff characteristics. minor must not be used.

Link to comment
Share on other sites
 

Fair enough, but the overcurrent characteristic has NOT changed (unless the RCBo is of a "C" curve design.

I must admit, I have previously removed a wylex 3036, replaced with a plug-in MCB, and issued MWC. Would continue to do so too, as I believe EIC is somewhat overkill for such a procedure. You`ve left the installation safer than it was; no matter what else is or isn`t done.

While preparing to duck behind my anti-missile shield; the "max Zs" question appears.

Now I ALWAYS use the 80% figure on the cert; for 2 reasons:

1. That figure is lower, as it allows for increased conductor temp., and therefore is not only a better figure for compliance; but also provides a "safety margin", i.e. if your Zs on "cold" cables passes the 80% figure; then, by definition, you`ve passed the 100% figure, which is based on "hot" cables.

2. For those who use NICEIC forms, if you open the front cover of any of the following:

IMN2, DPN4, DCN5, IPN2, ICN2

You will find a table of *****TABULATED***** values, along with a description of use. This clearly states that tabulated values should be used.

Sorry guys - but you`re wrong about 100%. Use 80% instead.

Trailer boy - you should know better :):):)

Link to comment
Share on other sites
 
SPECIAL LOCATION

:YGuiness Drink:YGuiness Drink:_|

OOOOh! Blushing:coat

Told you I would be behind my anti-attack thingy, that Steptoe left for me. :x]:)

In that case, I shall retract my statement, in its entirety (except for the bit about knowing better - that is still open to interpretation IMHO )

O)]:):x

You are a gent sir!:DApplaud Smiley

BUT..

it would have been more fun if we could have had a beer fight to sort it!

Guiness Drink:Y

Link to comment
Share on other sites
 

You want to throw red wine around - be my guest. Admin`ll have a hissy fit - you can`t get the stains out.:P:x]:)

But we are NOT chucking KME`s Guinness at each other - an offence such as that will have you hung, drawn, quartered, slaughtered & the remnants doused in petrol & lit. The ashes would then be stamped on & drowned in water.:x

YOU HAVE BEEN WARNED !X(

Link to comment
Share on other sites
 

I asked this question of ELECSA and they said an EIC would be required not just a MWC. I would imagine NICEIC will have a similar answer too.

Ian.

Link to comment
Share on other sites
 

ok thanks ian,ill take that on board,might just give them a call see if there'll tell me coz want to doing it right,

Link to comment
Share on other sites
 

thankyou for all your replies most hopeful cheers wayne

Link to comment
Share on other sites
 
 

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.

Link to comment
Share on other sites
 
SPECIAL LOCATION
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!:);)

Link to comment
Share on other sites
 

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.

Link to comment
Share on other sites
 
SPECIAL LOCATION
Fair enough, but the overcurrent characteristic has NOT changed (unless the RCBo is of a "C" curve design.

I must admit, I have previously removed a wylex 3036, replaced with a plug-in MCB, and issued MWC. Would continue to do so too, as I believe EIC is somewhat overkill for such a procedure. You`ve left the installation safer than it was; no matter what else is or isn`t done.

Concur, can easily put sufficient info on MWC to verify your alteration is safe without choppin down another rain forest's worth of paper!

While preparing to duck behind my anti-missile shield; the "max Zs" question appears.

Now I ALWAYS use the 80% figure on the cert; for 2 reasons:

1. That figure is lower, as it allows for increased conductor temp., and therefore is not only a better figure for compliance; but also provides a "safety margin", i.e. if your Zs on "cold" cables passes the 80% figure; then, by definition, you`ve passed the 100% figure, which is based on "hot" cables.

2. For those who use NICEIC forms, if you open the front cover of any of the following:

IMN2, DPN4, DCN5, IPN2, ICN2

You will find a table of *****TABULATED***** values, along with a description of use. This clearly states that tabulated values should be used.

erm? no it doesn't

it is generally accepted guidance that your measured values should be below these 80% values, BUT (a) they don't have to be & (B) it doesn't say write this 80% value in the column!

Sorry guys - but you`re wrong about 100%. Use 80% instead.

Trailer boy - you should know better :):):)

phtt!:|:o You been getting too much sun on them exotic holidays you keep going on bud!

sapping all your knowledge there... think you ought to invest in a caravan!]:)

In this particular occasion I shall have to disagree with you...

& IMHO I do know better BlushingO)

It IS the 100% NOT the 80% wot you wright on the cert.

Reasons:-

1/

Last paragraph of the "front cover of any of the following:

IMN2, DPN4, DCN5, IPN2, ICN2" reads thus...

Where the measured value of the earth loop impedance exceeds the relevant tabulated value below, further investigation will be necessary to evaluate the particular circumstances to confirm that compliance with BS7671 has been achieved.

e.g. In certain situations compliance CAN still be achieved with measured values greater then the 80% tabulated values. so by definition the Tabulated values are NOT the maximum permitted for compliance, and in this situation your certificate would have a measured value exceeding the max allowed!:(

2/

The column heading on page 3 of the cert says.

"Maximum Zs permitted by BS7671" which IS what tables 41.x pages 48 49 are!

3/

The NICEIC book inspection testing & certification, Chapter talks about how to fill in your schedule of results etc..

circuit detail's the bullet point for

Maximum Zs permitted by BS7671(ohm) states in its opening sentence...

This column should record the maximum permitted values of Zs, by reference to the limiting earth loop impedance values given in chapter 41 of BS7671, NOT to other tabulated 'corrected' values used for comparison with measured values obtained at ambient temperature.

4/

A couple of years back I was picked up on my annual assessment for writing the tabulated vales on my cert! Captain "NicEic" pointed out the column IS max, Not tabulated... (they do like to find one or to recommendations to give to you during each assessment) he pointed me to page 139 of my inspection book! and suggested if in any doubt about what to write in any of the boxes.. double check in the book, as it covers pretty well most of them!!:)

So I will be continuing to write the 100% not the 80% in the max permissible column!

;)Guiness Drink:x

Link to comment
Share on other sites
 
 
 
Andy™

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?

Link to comment
Share on other sites
 
Apache

Hello and welcome :)

Link to comment
Share on other sites
 

OOOOh! Blushing:coat

Told you I would be behind my anti-attack thingy, that Steptoe left for me. :x]:)

In that case, I shall retract my statement, in its entirety (except for the bit about knowing better - that is still open to interpretation IMHO )

O)]:):x

Link to comment
Share on other sites
 

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.

Link to comment
Share on other sites
 
SPECIAL LOCATION
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!

Link to comment
Share on other sites
 

Archived

This topic is now archived and is closed to further replies.

×
  • Create New...

Important Information

Terms of UseWe have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.