C50 Crabtree Circuit Breakers Specifications

Crabtree Electrical Industries Limited of Walsall, near Birmingham in central England sold miniature circuit breakers like the C50 series for use in homes and small commercial and industrial installations. The company filed its last active return in 2008 and was dormant until 2010 when it went into voluntary liquidation. The Crabtree line of circuit breakers with similar specifications as the old C50 line is today offered by Electrium of the UK, a Siemens company.


The original C50 line of circuit breakers is no longer carried by Electrium but there is an active secondary market in new and used breakers. The distribution boards populated with C50 breakers were very popular in the 1950s and 1960s and many are still in use since their quality was very high. They were manufactured to the British Standard BS 3871 which is now obsolete but Electrium carries replacements manufactured to current standards.

Specifications of the Original Breakers

The C50 Crabtree circuit breakers were a complete line of miniature circuit breakers designed for distribution board mounting. They were available as single pole breakers for branch protection or three pole versions as main breakers. The rated voltage was 250/440V or 240/415V. Branch breaker current ratings included 5A, 7.5A, 10A, 15A and 30A while main breakers went up to 60A. The interrupting rating of all these breakers was 3000A (coloured handle) or 4500A (white handle). The breakers were rugged, easy to install and had a special mechanism which reduced nuisance tripping. Working on the distribution boards was sometimes a challenge as, even with the breakers switched off, there were live parts which could be touched.

Modern Crabtree Equivalent Breakers

According to the Electrium catalogue, the new Crabtree miniature breakers have a similar operating mechanism as the original C50s but the case and way of mounting is different so that they are not interchangeable. The brand is now the Crabtree Starbreaker and the breakers have similar specifications as the original C50s but the interrupting rating is now given as 6000A. Electrium has a complete line of home electrical equipment under the Crabtree name but equipment wholesalers still carry the old C50 line, either new from their original stock or used from decommissioned old installations.

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