So in theroy you should measure the earth loop impedance before changing them. Personally I think the possibility of wrong size fuse wire is a higher risk than having the wrong ELI so even if I could not measure it I would still change them. 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. 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. 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. As with MCB's all MCCB's were manufactured by Delta and either branded MEM or Bill. They are identical apart from the logo and and a slight difference in the part number. You won't find any branded Delta, they never used that branding on any moulded case breakers.

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. Loadcentre – This was a new range introduced by Schneider but using the brand name of Square D. This is more of a commercial range with types B,C & D available (B type only in single pole). They have a breaking capacity of 10kA and. Later versions were branded as Schneider but are identical to the Square D. These will also fit the Qwikline II boards. After 1994 the British Standard of BS60898 came into effect and the range was changed to Types B, C & D and now included double pole mcb's as well. RCBO's were now being widely used and theses were available in Types B & C although it's rare to see Type B in use as most installations were commercial. So now you have a range of circuit breakers that are either branded MEM,Delta,Bill or Eaton. They may me marked either Type 2,3,4 or Type B,C,D. Some have a printed wrap around label and some have silk screen printing direct on the MCB. How many of these doctored fuseboards still exist without these metal fuse covers, justifying a recall? I am thinking of the fatalities in a Glasgow care home, thought to have been caused

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Memera 2000 – There are several different styles of MCB's in this range but all will fit any Memera 2000 board. In theroy you should test the loop impedance before changing. A 30A fuse will after many hours blow with 32A and in seconds with 100A and there is a curve linking the two. However with a 32A MCB there are two devices built into one. The thermal part works similar to a fuse but is slower than a fuse at high current so there is also a magnetic part which with the B rated MCB will trip between 3 and 5 times the thermal part so looking at 160A to trip it. To ensure a short circuit will trip the magnetic part we have to measure what the prospective fault current will be. Since ohms law comes in here we can actually measure the impedance (AC resistance) and that for a B32 should be 1.37Ω which allows for the volt drop of 5%. I have copies of a recent EICR and a follow up quote, these by a proven, registered electrician and are for a church, (C & G 2391 anyone?, and not the watered down version). The particular body is not relevant in this case, but the EICR is UNSATISFACTORY, one reason given is that fuses are not now permissible. ? There are around 5 Wylex fuse boards with plug in MCB's, these have gaps all around them because the original screw in covers over the original fuses, have been removed, being too shallow, so invalidating the IP integrity. 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.

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. More relevant, should suchlike electrical inspection reports only be carried out by a registered INSPECTOR, who must have a separate, periodic assessment?. 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. Delta decided to keep the brands MEM and Bill separate until 1998 when they finally phased out the Bill brand. What most people don't realise is that all the products that were manufactured were identical in both brands. Delta manufactured the products and either labelled them MEM or Bill. Qwikline – This is the most common Square D breaker and the part numbers will always start QO. Available in types 2,3 & 4 with M6 or M9 breaking capacities for early BS3871 breakers or types B,C & D with 6kA or 10kA breaking capacities. These styles have the push-fit electrical connection and push-fit mechanical connection. These are available in single, double and triple pole.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. 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. 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. 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. You can also buy MCB's pre-fitted with a pod in both the Memshield 2 and Memera 2000 ranges. These are usually just the 30mA size but field fit versions are availble is the following sizes:

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.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. 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?