overcurrent device

[sparkymatt1987]

on the schedule of test results, what is the kA overcurrent device short circuit capacity? Is it 33.0 kA as the installation is protected by a bs1361 type II fuse in the main cutout?

 

[Guest123]

It depends to which device you are referring. It it's under the section of 'characteristics of primary supply device' and it is a BS 1361 type 2 then yes it would be 33KA.

Each device is different though, with the ratings usually marked on MCB's for instance as an 'M' number or a number in a box i.e 6000 or 10000 etc etc.

 

[Deleted member 26818]

No, it would be the breaking capacity of whichever overcurrent device you are refering to, most commonly 6kA or 10kA.

 

[malcolmsanford]

Yes for a class II and 16.5 for a Class I

 

[Deleted member 26818]

Isn't 16.5kA the rating for a type tested DB?

 

[Guest123]

Isn't 16.5kA the rating for a type tested DB?

Almost....it's 16KA in accordance with BS 60439, annexe Za.

 

[Guest123]

"Part 3 of the Standard, BS EN 60439-3, deals with the particular
requirements for low voltage switchgear and control gear
assemblies intended to be installed in places where unskilled
persons have access to their use. This covers the supplementary
requirements for enclosure distribution boards suitable for indoor
use containing protective devices intended for use either in
domestic applications or other locations where unskilled persons
have access. Control and/or signalling devices may also be
included.
These distribution assemblies are for use on AC supplies, with a
nominal voltage to earth not exceeding 300V. The outgoing
circuits include short circuit protective devices, each having a
rated current not exceeding 125A with a total incoming load
current not exceeding 250A.
In the UK, such equipment is referred to as a ‘Consumer Unit’
and as such is covered by this Standard. However, additional
requirements from annex ZA of the standard call for the
assembly to have an additional test; this is known as the
‘conditional withstand test’. The condition is that the consumer
unit must withstand a 16kA short circuit fault when protected by
a 100A HRC fuse to BS 1361 type II. Further requirements are
addressed by this annex:
• Means of isolation to be via a manual double pole switch
disconnector
• Rated current of consumer unit is determined by current
rating of incoming device.
• Outgoing protective devices can be MCB’s, Fuses and/or
RCBO’s."