Max ZS for BS 3871's

[jimmer]

Does anybody know where i can find the max 100% ZS values for Type 1,2 and 3 BS 3871 mcbs? The OSG only has the 80% ones and just wondered if there was anywhere that had the 100% one so i dont have to re-calculate it.
Any help much appreciated

 

[Spudnik]

The max permissable values are in BS7671.

 

[Des 56]

The old 3871 are superceded by the 60898 So look them up on page 49 of the big red book and use the 60898 values
A B and C which equate to 1,2 and 3 of the 3871

 

[jimmer]

The old 3871 are superceded by the 60898 So look them up on page 49 of the big red book and use the 60898 values
A B and C which equate to 1,2 and 3 of the 3871

So values of type 1,2 and 3 3871 are now the same as 60898 type b,c, d?

 

[Des 56]

So values of type 1,2 and 3 3871 are now the same as 60898 type b,c, d?

No they are obsolete breakers and should be replaced with 60898s
I was saying to use the values of the 60898 instead
If you want the exact values then look at paqge 114 of guidance note 3

 

[Mr Mark Sparks]

jimmer just times the 80% by 1.2 to get 100%

des you can still buy 3871 mcbs crabtree c50 memshield 1 and others
why do you say they should be replaced with 60898?

 

[Des 56]

jimmer just times the 80% by 1.2 to get 100%

des you can still buy 3871 mcbs crabtree c50 memshield 1 and others
why do you say they should be replaced with 60898?

Maybe I am jumping the gun stating they should be replaced,perhaps advise to be replaced, would have been a better phrase
They are not listed in the 17th and it is arguable whether they are compliant or not,even though they are still available
I have pasted a bit of info that relates to this,which helps explain my replies

BS3871, which specified the miniature circuit breakers Types 1 to 4 was withdrawn in 1994 and has been replaced with BS EN 60898:1991 (EN stands for "European norm"), although it is possible that circuit breakers to the old standard will still be on sale for five years from its withdrawal. In due course, it is intended that only types B, C and D will be available, although it will be many years before the older types cease to be used. Short circuit ratings for the newer types will be a minimum of 3 kA and may be as high as 25 kA - the older types had short circuit ratings which were rarely higher than 9 kA.

I dont think it is a safety issue,more of an observation that they are old hat and updated devices would be preferable
regards Des

 

[sixfingers]

Hi Des

Have copy of GN3 and page 114 does not seem to have values on? Copy of GN3 is 2008s!

 

[scotsparky]

sixfinger there is a great table of Bs3871 &bsen60898 Mcb Max Zs readings in the OSG near the back. Havent got the book on me at mo but its there.

 

[Spudnik]

Des,

Not wanting to split hairs, but nowhere in that info does it say that 60898's are preferred over 3871's.

I know they are now becoming extinct, but on an existing install, surely if all circuit criteria are met then there should be no reason why they would not comply?

 

[Des 56]

Des,

Not wanting to split hairs, but nowhere in that info does it say that 60898's are preferred over 3871's.

I know they are now becoming extinct, but on an existing install, surely if all circuit criteria are met then there should be no reason why they would not comply?

I dont disagree with your statement
I am making an opnion (in a poor way may I say)that when something becomes obsolete, then upgrading to the present day standard, could be advised ,otherwise we have to keep reference to information of those older standards for ever and a day
Confirmation of this, was the request in the opening post, for the zs of an unlisted obsolete BS mcb
I say it is arguable whether they are compliant because compliance may be difficult to confirm if they are not referenced

I think the preference of 60898s over 3871s is demonstrated by their ommision from the regs


By the way
My apologies for the page reference
The guidance note 3 page 114 was for my 2006 print (16th ed)

 

[Spudnik]

Understood.

 

[ian.settle1]

No they are obsolete breakers and should be replaced with 60898s
I was saying to use the values of the 60898 instead
If you want the exact values then look at paqge 114 of guidance note 3

You can not use the values of 60898 as the maximum tripping current was different for 3871 types thus a different max Zs.

just calculate the max Zs - 230/max current for breaker as it is found for 60898 MCB's

eg 60898 type B mcb should trip between 3-5 times mcb rating thus for 6A type B 230/30=7.666 as per regs

thus a 3871 type 1( trips between 5-7 times I think) - For 6A mcb type 1 230/42=5.4

 

[thesonandheir]

Hi guys, James here with first post!


Does anyone know the max permitted Zs for a 32A type 4 3871 mcb?

Many thanks to anyone who can help, cheers


James.

 

[scotsparky]

sixfinger there is a great table of Bs3871 &bsen60898 Mcb Max Zs readings in the OSG near the back. Havent got the book on me at mo but its there.

Found it on Page 103