Maximum Zs

[riccer]

I am filling out my first domestic electrical installation form to the 17th edition.

And I cannot seem find out what the maximum Zs permitted by BS 7671 value is.

Could you please help me with this.

 

[willosparky]

maximum Zs or maximum Ze

 

[ian.settle1]

I am filling out my first domestic electrical installation form to the 17th edition.

And I cannot seem find out what the maximum Zs permitted by BS 7671 value is.

Could you please help me with this.

Zs for what type of protective device?

As said in one of your previous postings if you don't know what you are doing leave it alone before you hurt your self or kill someone else.

 

[Ballcock]

I am filling out my first domestic electrical installation form to the 17th edition.

And I cannot seem find out what the maximum Zs permitted by BS 7671 value is.

Could you please help me with this.

After the un-helpful replies you have received, you will find what you need in App. 2 of the on-site guide.

hope this helps

 

[Amp David]

Use the index, thats what its for, that is if you've got a copy of the regs?

 

[solo2771]

Maz Zs varies wth the type of protection used ie fuse, mcb
we were told to use the tables in the regs book and as a rule of thumb multiply it by 0.8.
If using mcb's the higher the value the lower the max Zs

 

[Mac]

I am filling out my first domestic electrical installation form to the 17th edition.

And I cannot seem find out what the maximum Zs permitted by BS 7671 value is.

Could you please help me with this.

17th Edition Maximum Ze & Zs Values Good luck mate.Too many grumps on the forum

 

[Ballcock]

Use the index, thats what its for, that is if you've got a copy of the regs?

Didn't you once have to learn?
I joined this forum with the hope of passing on some information, and in turn learning a bit , yes that's right, I'm an electrician of 25 years that's still learning.
Wouldn't you rather someone had the sense to ask, instead of diving in and getting hurt?

Yours
Vinnie

Apologies for the language Mods, sometimes it's the only way

 

[scotsparky]

Try page 103 on OSG the figures are pre calulated at 80%

 

[pevvers]

The fact that it says maximum Zs permitted by BS7671 should give you a clue that the corrected 80% values should not be used for this column.

All the tables that you require for this column you'll find in part 4 of BS7671.

 

[Spudnik]

This forum is for EVERYONE to use, therefore i would respectfully ask that answers are kept civil.

If you do not wish to help then DO NOT POST.

 

[brucelee]

17th Edition Maximum Ze & Zs Values Good luck mate.Too many grumps on the forum

just want to say cheers for posting this link mac its a good reference.saves time pouring over regs a lot quicker , easier to find what your looking for nice one mac

 

[promaxia]

with the new requirments 17th all consumer units require mcbs to bs 60898 or rcbos to bs 61009.BS 7671 deals with the magnatization effect of the breakers.Its not rocket science to know off your head the values of the 9 sizes of breakers 6,10,16,20,25,32,40,50,and 63.learn all of these on b type then for c type its half and then for d type its half again.What is valuable to know that for any circuit with a dissconnection time of 5 sec.ie 40a 50a 63a and a sub distribution circuit yoy can use the thermal characteristics of the breaker .this would be a departure from bs 7671 but its still within electricity at works regs 1989.

 

[wislum]

Hi Riccer,
I have trained a number of so called electricians and the have come up short on testing most think they know it all and cant be taught anything new. Those generally fail the 2391 at least 3 times. What I am trying to saqy is IF IN DOUBT ASK which is just what you have done and good on you for it.
The answer to your question is use the figures in the big red book page 48 and 49 for table 41.2 forfuses with a dis time of 0.4secs and table41.3 for MCBs and table 41.4 for fuses with a dis time of 5 secs. The 80% isue is the reading you get must not exceed that 80% of Max figure to be safe( 80% allows for sme correction factors such as temperature)

I train and I am still learning the only way to adapt to changes

 

[sugarman]

I am filling out my first domestic electrical installation form to the 17th edition.

And I cannot seem find out what the maximum Zs permitted by BS 7671 value is.

Could you please help me with this.

look on page 49 of our big red book my friend ,,,,looking under what type of protective device you have,,,,ie....a 60898 type b mcb rated at 32amps is ,,,,,1.44 ohms.....
check it out...... good luck..