inspection & test, disconection times & maximum zs allowed

[vincef]

Hi,

on a tn system, 238vs, would the disconnection time be 0.4s or 0.2s, i thought as over 230vs it should be 0.2s, but working with another engineer who disdagreed & pointed out tables in bs7671 show 0.4s to 5s?
Also when completing certs should you include the 80% or not in the maximum allowed zs box?

 

[Jay Sparks]

Hi,

You use the max Zs from the regs book for the cert and you only apply the 0.8 to these readings when your comparing your measured Zs results. However you dont need to use the 0.8 rule of thumb when comparing your measured results with the ones in the osg, as these have already been done for you.

Jay

 

[tony mc]

You also use the 0.4 sec for TN systems as Uo is 230 volts .

 

[telectrix]

disconnection time for circuits<32A is 0.4 secs . on a TN system. your 238V is classed as 230V nominal although it's really 240V.

 

[SPARTYKUS]

No it isnt, we harmonised with europe, especially Greece, so it must be exactly 230 all the time.

 

[telectrix]

don't get me going on yewrup. i''lll end up getting a ban, bloody foreign bureaucrats telling us what to do, we need another agincourt, trafalgar, waterloo, el alamein, grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

 

[telectrix]

the foundations of Westminster Abbey are shaking. it's Winston turning in his grave.