minor works high Zs Values

[dean7828]

test, cant seem to post????

 

[Flanders]

The above post as worked

 

[dean7828]

ok cool, this will be the second attempt,
i have a circuit tested to be too high Zs Values for the existing protective divice, its an addition to an existing radial circuit, however the new addition is protected by a 13a spur, the max permitted Zs value for the BS1362 is acceptable.


my question is this! is it acceptable to use a BS1362 as the circuits overcurrent protective device for the modified circuit when completing a minor works cert, cant say I have never given it much thought until now????

 

[Flanders]

OK so the extra part of the circuit you have added from the 13 amp FCU sounds acceptable as long as the BS 1362 fuse will disconnect the circuit in 0.4 of a second the problem you have is that you have fitted the 13 amp FSU on the circuit that the OCPD supplying that needs to disconnected the circuit within 0.4 seconds if is does not then it is unsafe , If there is 30mA RCD protection you may be able to get away with it , but it Is not good practice just the really on an RCD for fault protection

 

[telectrix]

looking at it logically, if the 1362 fuse will diss. in 0.4 secs for the extension part of the curcuit, and the Zs at the FCU is within the max. for the OCPD at the origin of the circuit, then it should comply. tin hat firmly on.

 

[Flanders]

I agree with you Tele but if the Zs at the FCU is to high for the OCPD for that circuit then the OP has a problem

 

[dean7828]

I agree with you Tele but if the Zs at the FCU is to high for the OCPD for that circuit then the OP has a problem

hi thanks for the reply, yes the Zs is well within at the point of the spur, its just the new circuit which is high, it will require investigation but should do for now.

 

[Brightspark2]

Your circuit starts from the fcu so that is the OPD information you add into your minor works.

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[Simonslimline]

When you tested Zs, was it a low current no trip test?

 

[Octopus]

Your circuit starts from the fcu so that is the OPD information you add into your minor works.

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This could start an interesting debate!

 

[Flanders]

This could start an interesting debate!

so if its a new cicuit ,not an addtion or modification to a circuit then an installation cert may be required
Athough even saying it ,an eic seams over the top for such a small job , but thems the rules

 

[Octopus]

so if its a new cicuit ,not an addtion or modification to a circuit then an installation cert may be required
Athough even saying it ,an eic seams over the top for such a small job , but thems the rules

I think the definition section of bs7671 is required here. Think it says a circuit starts at a fuse board our similar

 

[Brightspark2]

I think the definition section of bs7671 is required here. Think it says a circuit starts at a fuse board our similar

An assembly of electrical equipment supplied from the same origin and protected against over current by the same protective device.

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[dean7828]

When you tested Zs, was it a low current no trip test?

i tested both high current and low current but both was high,

 

[TJ Anderson]

Can't see any problem with that at all. list BS1362 as OCPD and list cable size from the load side of spur. If Zs is low enough for fuse rating and cable protected then it is definately ok.

 

[Flanders]

hi thanks for the reply, yes the Zs is well within at the point of the spur, its just the new circuit which is high, it will require investigation but should do for now.

Yes as you say may nead investigation to find if the Zs is is high due to a poor connection or if infact it is similar to the calculated value for the characteristics of the cable you have installed if the test reading works out to be correct then it sounds to me that there is nothing wrong with your installtion andyou can fill in the minor works as you suggested

 

[Risteard]

What I have done before is list the protective device (e.g. BS 1361 HRC fuse) for the circuit on the Minor Electrical Installation Works Certificate, then in the box asking what work was carried out I will declare that it is connected to a Fused Connection Unit protected by whatever rating of BS 1362 fuse, and that the maximum Zs for 0.4 second disconnection is whatever (depending whether 3A or 13A).

Then there really can't be any comeback as you have clearly explained this on the Certificate.