WYLEX WYB “SK” Plug in MCBs

Older, long obsolete range of WYLEX BSEN60898 MCBs for domestic & light commercial use.

Not to be confused with the earlier ‘push button’ Wylex SK plug in MCBs, this type have a resettable toggle similar to more modern MCBs.

These were fitted in their thousands as a quick way to upgrade older wylex BS3036 rewireable fuse boards.

Still coming across a large number of properties, both domestic & light commercial where these are fitted into old BS3036 boards.  The boards to which these breakers fit have no facility for RCD protection and serious consideration should be given to simply upgrading the board, however this guide is given in case you need to know what will get you out of an emergency!

Wylex SK series plug in circuit breakers are 3000A breaking current (3kA) and the range is as follows:

• 60898 Type B MCB = 6A, 10A, 16A, 20A, 32A, 40A,

Wylex WYB “SK” Plug in MCB Specifications

Breaking Capacity According to BS EN 60898 & IEC 60898: 3kA (3000A)

Rated Voltage: 240V AC

Maximum Operating Temp: 55 degrees C (Assumed?)

Part Numbers:

• WYB6 – 6A Type B MCB  (WHITE)
• WYB10 – 10 Type B MCB  (GREY)
• WYB16 – 16A Type B MCB  (BLUE)
• WYB20 – 20A Type B MCB  (YELLOW)
• WYB32 – 32A Type B MCB  (RED)
• WYB40 – 40A Type B MCB  (ORANGE)

Wylex SK Plug In MCB Dimensions (WYB Series)

All Wylex SK plug in MCBs share a common sized body, no matter what the rating

The difference between each rating circuit breaker is that they have a different arrangement of the ‘push in’ blades on the back of the circuit breaker. 

NOTE that the BS3036 fuse cover on the Wylex boards WILL NOT fit once any of the BS3036 fuse cartridges have been replaced for any plug in MCB.  The plug in MCBs are significantly deeper than the BS3036 fuse cartridge.

Each circuit breaker is assigned a different colour based on it’s specific rating.  See the list above for the colour combinations.  These are a ‘throw back’ to the colours used to identify BS3036 fuses, something which these MCBs were intended to do.

The differing colour bases have a unique pin arrangement so that, for example, a 32A MCB will only fit into a RED coloured base.  You could not fit a 16A MCB to a RED base, only BLUE.  This prevented people inadvertently fitting higher rating MCBs to thinner cables.

The height (top to bottom) of the MCB body is: 60mm

The ‘Depth’ which is the total front-to-back measurement (of MCB body): 70mm

• WHITE 6A SK Plug In MCB Blade Width =
• GREY 10A SK Plug In MCB Blade Width =
• BLUE 16A SK Plug In MCB Blade Width = 8mm
• YELLOW 20A SK Plug In MCB Blade Width =
• RED 32A SK Plug In MCB Blade Width = 9.6mm (be aware pin location differs from 40A below)
• ORANGE 40A SK Plug In MCB Blade Width = 9.6mm (be aware pin location differs from 32A above)

Alternative Fitments?

The WYLEX SK plug in series of circuit breakers are designed as easy upgrade fitments to BS3036 rewireable fuse boards, commonly fitted between 1970s-1980s. 

• WYLEX WYB ‘ABB’ plug in MCBs – Direct Swap – blade arrangement on rear is same so can share base plates
• PROTEUS plug in MCBs – Fit same boards, however base ‘blade’ dimensions are different so plastic base plate requires changing (these are same dimensions are GE Mini Trip plug in MCBs below)
• GE Mini Trip plug in MCBs – Fit same boards, however base ‘blade’ dimensions are different so plastic base plate requires changing (these are same dimensions are PROTEUS plug in MCBs above)

WYLEX Manufacturer Site: WYLEXs manufacturer page

BUY Wylex SK Plug In MCBs at the following links, be aware that the 40A MCBs are fetching a premium now that the newer 40A MCBs have ceased production: 

Circuit Breaker Specialists – SK Plug in MCB 40A

Circuit Breaker Specialists – SK Plug in MCB 10A

32A Wylex BS3036 Replacement MCB – WYB32 @ Wentvale Electrical