3036 mcbs

Robo1401 · Dec 12, 2011

Hi there, i was wondering if anyone could help me out quickly, BS3036 fuses that still use the original carrier but have been replaced with plug in mcbs....any idea on the BS number of these? Cant find em in the regs book and trying to find max Zs...? Cheers

Deleted member 19807 · Dec 12, 2011

should be marked on the mcb's could be either 3781 or 60898

Robo1401 · Dec 12, 2011

First thing i checked but nothing on em

cbw · Dec 12, 2011

This type is as Hifly suggested a standard B Curve 60898

needasparks · Dec 12, 2011

As other said, if its switch type wylex its B type 60898 or if its the older push button type its 3871 (believe was type 2)

MarkieSparkie · Dec 12, 2011

I assume you mean BS3781 cartridge fuses and MCBs NOT BS3036 semi-enclosed rewirable fuses.

Time curves for BS 3871 devices
The time/current curves for BS3871 MCB's you're looking for are in 16th edition of the wiring regulations BS7671:1992 AMT 2, BYB, or earlier.
Time/Current Characteristics:
BS3781 40A Type 1 MCB, 0.1 to 5s = 160A
BS3781 40A Type 2 MCB, 0.1 to 5s = 280A
BS3781 50A Type 1 MCB, 0.1 to 5s = 200A
BS3781 50A Type 2 MCB, 0.1 to 5s = 350A

The older style MCBs were BS 3871, and were numbered Type 1, 2, 3 and 4.
The characteristics for the old type are similar but not the same as for the new BS EN 60898 versions.
Type 1: 2.7 - 4 In, Type B: 3 - 5 In.
Type 2: 4 - 7 In, Type C: 5 - 10 In.
Type 3: 7 - 10 In, Type D: 10 - 20 In.
Type 4: 10 - 50 In.

During the change over of the standards, manufacturers were allowed to use the new BS EN 60898 designations on the old BS3871 devices, if they were within the limits specified.
For instance a Type 1 is within the specifications for Type B.
Types 2 and 3 are within the specifications for Type C.
However Type 4 is outside of the specifications for Type D.

The value of Zs in BS7671:1992 AMT 2, are at a nominal voltage 230V as required in later versions. However, be careful when using the Zs values from old versions of BS7671, the nominal voltage will be 240V. The voltage is relevant because the current required to disconnect in the correct time divided into the voltage gives the ZS max values for the CPD. A nominal voltage of 240V will therefore result in a proportional higher Zs max, than now allowed. If you have the old Zs values divide them by 240 then multiply by 230 to get the new values.