Fuse type and rationg for BS3871 push button MCBs

[jmaddock]

I have just been doing some work on a CU which has BS3871 push button MCBs and all I can see on the things is Wylex SK and 6A, how do I tell the type and the breaking capacity

 

[Deservices]

I think they are a type 2 which is similar to a type b MCB, but don't have the info with me it's in the 17th edition book.

 

[NEZ2490]

• OSG Page 57 TABLE 7A​
  
  
  
  

 

[tony mc]

Must be a different OSG to mine have a look at page 71.

The push button 3871 were replaced by BS EN 60898 and have a Ics with a letter M followed by a number 1 1.5 3 etc giving you the rated SCC capacity in ka!

 

[somersetsparks]

The push buttons are usually B-types for which no Max EFLI's are given in the book. I think some of them are only 1Ka and are usually marked S1A for 1Ka etc.

 

[somersetsparks]

Just had a quick look - the 5A are M1 rated 'type B' 15-45A are M2 rated.

 

[jmaddock]

Just had a quick look - the 5A are M1 rated 'type B' 15-45A are M2 rated.

Thanks for the info I could not find it for looking

 

[NEZ2490]

Must be a different OSG to mine have a look at page 71.

The push button 3871 were replaced by BS EN 60898 and have a Ics with a letter M followed by a number 1 1.5 3 etc giving you the rated SCC capacity in ka!

Sorry was quick reply on way out of door you are correct in your advice. oops :90:

 

[fuzzybreeches]

You don't see these often, but I was having a look at a lighting fault today, and found these Wylex BS3871 push button MCB's. I remember the electrician who trained me saying that these had been made illegal, as they were prone to malfunction (i.e. delayed cutoff time, or inappropriate activation). This was why Wylex brought out the ones with dolly switches.

I've tried a bit of research on the Net, but found no info at all. Apart from this thread, and a similar one on the IET forum.

Can anyone add to this little mystery, or is it an urban legend?

 

[Deleted member 26818]

Urban legend.

 

[rattlehead85]

Nothing wrong with push button ( pop out) MCB as long as they pop when the little test button mechanism is operated, there is no sticking of the button and it re-latches then they are suitable for continued use. Just make sure your Zs values do not exceed the tolerance of the device.