bs3871 zs value ?

[burntwire]

Can anyone tell me the zs value for a bs3871, 32 amp, b type mcb ? or where it is in the 17th, cos I cant find it !!

 

[burntwire]

Ive been told there isnt a type b, but it says B32 on it !

 

[ericmark]

If you take the 48/In divide by 240 times 230 then you get the 46/In given in new 17th Edition so 46 divided by 32 gives 1.4375 ohms Table says 1.44 ohms same applies for example Type 1 so 57.5/In so 1.796875 ohms for 32 amp using excel you can quickly make a table.
Eric

 

[dingbat]

If you take the 48/In divide by 240 times 230 then you get the 46/In given in new 17th Edition so 46 divided by 32 gives 1.4375 ohms Table says 1.44 ohms same applies for example Type 1 so 57.5/In so 1.796875 ohms for 32 amp using excel you can quickly make a table.
Eric

Blimey, make it hard for yourself why don't you?!!

The Zs values are calculated by Uo/Ia, as can be seen from the equation on page 48 of the 17th Edition.

If you have the old values, they were calculated using 240V , whereas the new ones are calculated using 230V, so simply multiply the old values by 230/240 (multiply them all by 0.96 and you'll be close enough.)

 

[GaryMo]

Looking at Easycert, the software I use to create certificates and reports, it has a BS3871 B32 at 1.44ohms.

EDIT - I'm not convinced they have it correct though as I believe a type B is the same as a type 1, a type 1 has instantaneous tripping characteristics of 2.7-4.0 x In.

That would mean 230/(4x32) = 1.79ohms

Guide to circuit breaker standards

 

[burntwire]

thank you both very much for your replies. Do you recommend easy cert ? I currently hand write all my test certificates, however i'd like a more proffesional system. Can I use these with Elecsa ? or do i need an elecsa logo on test sheets i produce ? (im registered with elecsa )

 

[Spark123]

I must admit I thought the type B came in with BSEN60898 devices, the old BS3871 being type 1, 2, 3 or 4.
The 1.44ohms you get from the easy cert is the same as whats in the regs for a BSEN60898 type B device.

 

[GaryMo]

Yes, I noticed that.
I also though BS3871 MCB's came as types 1-4 only but the document I posted above says otherwise.

 

[GaryMo]

Do you recommend easy cert ? I currently hand write all my test certificates, however i'd like a more proffesional system. Can I use these with Elecsa ? or do i need an elecsa logo on test sheets i produce ? (im registered with elecsa )

Yes, I would recommend EasyCert. Have a look at Tysofts homepage and download the evaluation to have a feel for the software.

Tysoft EasyCert

We're with the ECA and I don't have a problem adding the ECA logo to all certificates or reports I produce.

 

[RF Lighting]

Guess what?

I've got a photo of one

 

[ericmark]

The MCB is designed to magnetically trip at a set multiple of the designed thermal over load current. So putting it in simple format.
Type Multi fig x/In 240V x/In 230V 32A 240V 32A 230V
Type 1 X4 = 60 or 57.5 Max ELI=1.875ohms 1.796875 ohms
Type B X5 = 48 or 46 Max ELI=1.5 ohms 1.4375 ohms
Type 2 X7 = 34.28571 or 32.85714 Max ELI=1.071429 ohms 1.026786 ohms
Type 3-C X10 = 24 or 23 Max ELI=0.75 ohms 0.71875 ohms
Type D X20 = 12or 11.5 Max ELI=0.375 ohms 0.359375 ohms
Is that any better then. Sorry seems it don't like tables or ohm sign! Fancy having an electrical forum that can't accept an ohm sign!
Eric

 

[securespark]

Yes, I'm with RF here. Type B/C/D breakers were introduced under the old standard BS 3871, alongside Types 1-4.

Although there was not a Type A, as "A" denotes the unit of current measurement.

 

[pompeygit]

Even easier turn to page 111 of the new GN3

 

[Spark123]

P111 of GN3 gives max measured values, not max tabulated values.
There is a factor of 1.24 difference. (1.24 given for a 60ºc temp difference between max and measured)