Dorman Smith 3871?

[SparkyBen]

Was just wondering if anybody could help me out?

The dorman smith 3871 Types 1-4 circuit breaker are they acually legal to use? as im trying to do a little research on them. Is there any thing in writing to say they are not safe? In my experience with them i have found them not to trip under fault conditions. Any one else had this problem?

 

[ricicle]

Is this genuine research or are you just trying to justify using some old equipment on a new job?

I'm not being funny - just curious

 

[SparkyBen]

The company im working for use them in 10kva transformers! was looking for a little amo. I know they are not safe have seen it for my own eyes. Just wondering if there is any documentation that any one has seen?

 

[ricicle]

Off the top of my head I can't remember the exact figures for types 1 - 3, but type 4 require 50 times nominal current rating for instantaneous trip.
Good for loads with high inrush (eg trannies) but could be a problem for circuits requiring fast disconnection.
Not sure of the implications of using old BS mcb's but as long as circuit fulfils Zs for device (for required disconnection time) then I can't see a problem (I await correction )

 

[passerv]

BS 3871 had rather low breaking capacities didn't they, although I expect I'll be corrected.

Nice PDF file here.

http://www.beamainstallation.org.uk/assets/pdfs/CircuitBreaker.pdf

 

[securespark]

You would also have to ensure the loop was low enough for the particular breaker.