Mini circuit breakers are triggered by overcurrent - electrical current that exceeds a designated safe current and makes use of a relatively robust mechanical mechanism designed to minimise failures and false alarms. Moulded case circuit breakers ( MCCBs) have a very similar function to MCBs but they also have a higher capacity. MCBs are all sub-100-amp devices and are designed for low voltage circuits, so their trip curves cannot be adjusted. By contrast, MCCBs feature adjustable trip characteristics, which means that they can be used with higher voltages – as much as 2,500 in some instances. What is the Difference Between MCBs and ELCBs? Residual current devices ( RCDs) are a different form of electrical safety equipment. While MCBs have a general function, RCDs are specifically built to protect against the frequently fatal risk of electrocution from touching exposed wires or incorrectly earthed cables. They operate directly within electrical circuits to detect faults and cut off potentially hazardous currents.

All MCCB's in MEM's Memshield 2 range or Bill's Talisman Plus range are branded as such. Even though Eaton bought out Delta in 2003 they maintained the old branding until they came out with the latest range, Memshield 3. Even though they are using the Memshield brand all breakers are now marked as Eaton. Still Confused? MEM first started manufacturing circuit breakers in 1965 and were one of the UK's biggest names in circuit protection. Now they go under the trade name of Eaton but still use the MEM name on some products. Memera 2000AD – These have a narrow terminal and only fit boards specifically marked Memera 2000AD. They won't fit in older boards. ELCBs (earth-leaking circuit breakers) use earthing as their primary method of controlling electrical current and preventing electrocution. They work by detecting any stray voltage on the enclosure of a device and then breaking the circuit if it exceeds a designated level. They perform a similar function to RCDs, but the latter detect stray voltage directly and so are now more favoured by electricians. What is the Difference Between MCBs and RCDs? An MCB is designed to protect against both overloading and short-circuiting. These are detected differently using separate processes. Overload protection is provided by the bimetallic strip using thermal operation, whereas short-circuit protection is provided by the tripping coil via electro-magnetic operation.Specifications matter more than brand when choosing MCBs, so in theory, you can use any component that is compatible with a particular device. However, mixing brands in the same installation is not recommended as it makes testing less reliable and can invalidate warranties and installation guarantees. Why are MCBs Preferred to Fuses? In the late 1980's Crabtree were looking to replace the outdated (but still widely used) C50 range. What they came up with was the Polestar range and it was a great success in commercial and industrial applications. Qwikline II -This range superseded the original Qwikline but the range was not as broad with only types B & C available and a breaking capacity of 6kA. These only come as single pole. Later versions were branded as Schneider but are identical to the Square D. They will also fit Loadcentre boards.

Bill Switchgear was probably one the oldest British electrical brands and was especially known for bigger switching devices like triple pole fuse switches and switch fuses and LV panelboards. The company was aquired by Delta in 1973 who also owned another well known brand, MEM.A new range of Polestar was launched in 2012 and called Polestar Compact. Although the new range was 16kA rated due to advances in technology it was significantly slimmer and is not interchangeable with the older style.

Memshield 2 – These are also a commercial breaker and come in types B,C & D. These also will fit into all Memera 2000 range boards. Initially the range was made to BS3871 standards so Types 2 & 3 were available from 6A up to 63A in single and triple pole. RCBO's were also available but they were initially referred to as MCB/RCD units as the term RCBO was not really established as yet. Confused? Well it gets worse because by the time that Delta/Eaton decided that they needed to manufacturer some of the older products to keep the peace with customers the British Standard BS3871 had changed. Previously all MCB's had been marked with a ‘Type' (either 1,2,3 or 4) but BS3871 had changed so that Type 1 MCB's were no longer used and Types 2,3 & 4 were now Types B,C & D. Domae – This was the final range of MCB's branded as Square D. Unusually they are not the push-fit type which was what Square D was really known for. This range just uses a standard din-rail clips and was a ‘competitive' product aimed purely for the domestic market. Later versions were branded Schneider but are identical to the Square D. Memshield 1 – These are a commercial breaker and come in various types (Type 2,3,B,C & D) depending upon the age. Most are M9 rated.

The Polestar range of breakers was unique because they had a higher than usual fault rating of 16kA where standard breakers at the time were 6kA and 9kA. What this meant was that Polestar could be used in areas where a high kA was required without having to use Moulded Case Breakers (MCCB's) or HRC fuse carriers. Crabtree Polestar breakers are also unique in that they are much wider (25mm) than a standard mcb (18mm). This extra width was needed for the bigger arc splitter to allow for a higher kA rating. Fortunately the situation with Bill and MEM MCCB's is not as confusing. Firstly MCCB's are made to a different standard to MCB's, BS60947-2. Whilst that standard has been updated to allow for new technologies it still remains as the current British Standard. To test an MCB after installation, you will need a suitable portable voltage meter from a reputable manufacturer. Electricians also recommend manually inspecting the switching mechanism of MCBs before installation; typically, a greater degree of pressure is needed to open and close more reliable models. Can You Mix MCBs? Square D was bought out by Schneider in 1991 and although they changed the appearance of the circuit breakers the later versions will still fit the older boards. Not all pods are the same, some have long leads for triple pole boards and some have short leads for use in domestic boards. Also worth mentioning that the pods will fit the Memera 2000 range of MCB's as well but only the part numbers that start ALB or ALC.