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. 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. However, just to add a little confusion, some MCB's were discontinued whilst under the MEM brand but due to complaints from customers, specifiers and electrical wholesalers the company had to start manufacturing again. Some of these products are branded Delta and from 2003 some of these products are branded Eaton when they company was bought out yet again. In the late 1980's Crabtree were looking to replace the outdated (but still widely used) C50 range.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. 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.The older RCD does seem to be affected by spikes, so likely a SPD would stop it, but a consumer unit is a type tested distribution unit, and to retain the type testing only items recommended by the manufacturer can be used, even if they seem to fit. 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. 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.

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. 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. 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.

Memera 2000 – There are several different styles of MCB's in this range but all will fit any Memera 2000 board. 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. 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. 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. Otherwise, I'm not quibbling the need for proper spur to garage, which will separate off two freezers from kitchen, but how do you people feel about this diagnosis? My own insulation tests with mega meter to each unplugged appliance have found no resistance issues, which given he found no wiring issues, leaves no obvious cause except as he thinks maybe too much total freezer earth leakage. Intermittent faults like tripping can send you mad as we all know, is this a good course of action?

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. So question one does it pass when tested with a RCD tester? If so what makes you think it is faulty? I am sure the one in my old house was tripping due to surges when a neighbour was welding. Two identical RCD's would hold for 18 months without a problem, then trip for seeming no reason for couple of weeks, then again two years no tripping.

Residual current circuit breakers - with overload protection (RCBOs)

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: but mounted above the old Wylex fuse boxes, however done before the rules changed as to electrical equipment in the control of an ordinary person. But still today we have isolators before the CU to comply with HSE rules an live working, so not sure if we can still mount SPD or RCD in separate box before or after main CU? 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. For the person who asked about Smartmeter, yes one fitted in last year and quite close to CU (2 meters?). Though similar episode of nuisance tripping preceded its installation and went away of its own. What are you thinking about this?