Came across a Dorman Smith Loadmaster DB today on a domestic. I had a good look at the info on a breaker but I'm sure it didn't state what type it was (i.e. 1/2/3/4 or B/C/D)

The breaking capacity was M1.5 which doesn't seems to correspond to any of the info I have found on line or from previous threads which seem to suggest that they are generally M3. Does this help to identify the type designation of 3871 that this is?

Any help much appreciated as want to make sure I get my facts straight!

That would appear to be a BS3871 MCB rated at 1.5kA. Any other information on the breaker? A lot of these were the dreaded Type 4 types.

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John Peckham

http://www.astutetechnicalservices.co.uk/

Unfortunately not John, that's the trouble!

Definitely 3871 1.5kA but no other ino on it.

The original loadmaster was type 4 and breaking capacity of M3 (except 5A), toggle was 8-10mm wide (pic: http://www.dormansmithswitchge...ts/loadmaster_mcb.gif) and ratings of 5, 7.5, 15, 30, etc


See here for zs values: http://www.dormansmithswitchge...dmaster_datasheet.pdf

The loadmaster series 15 was type 3 and M4.5 breaking capacity and the toggle was 15-20mm wide (pic: http://electricsoutdoors.co.uk...ges/5076dc31f2cf0.jpg) and ratings of 6, 16, 32 etc

Zs values for type 3 are the same as type C but see here http://www.dormansmithswitchge...master-LXV_Zs_data.pdf for manufacturers data

Loadmaster was used in late 60's / 70's. series 15 came in later on in 80's. However breakers got mixed and matched, boards that are marked as series 15 often contain a mix of the two types, as series 15 is no longer available, but some ratings of original loadmaster are still made

Check your thermal withstand if using reduced CSA cpcs on the loadmaster breakers

Thanks for the info. Phoenix. I was thrown a little by the 1.5 rating on the 5a as that's the only one I checked and it didn't correspond with any of the info I'd found. I did see the data sheet and it is that series.

Cheers.