Dorman Smith faulty RCBO's???

[adslev]

Right fellas advice/ wisdom required!!
Im currently testing a large installion 20x 16way 3ph boards. Anyway the majority of the circuits are protected by bs 61009's, Dorman Smith to be exact.
However when i do my Zs test the rcbo trips. Its the new megger 1730 so this shouldnt happen, been on the phone to megger themselves and their technical department haven't been much use. Have any of use experienced similar problems? When testing circuits protected by mcb's 60898's it gives me a reading so im getting a little frustrated, especially as my first 1730 imploded on its first outing! Hoping its not the tester as i could do without the hassle and its the rcbo itself thats at fault, have tested quite a few of these as well which don't trip at 1x its rating, the ramp test brings up 33mA or there abouts so I personally don't like them. Sorry for going on but its been a long week
Thanks for any input as it would be greatly appreciated!!

 

[topquark]

Well, any that ramp test at 33mA are no use to man nor beast (back to the wholesalers for replacements). The only other way to record your Zs would be to calc from Ze+(R1+R2) and record that.

 

[adslev]

yeah came across quite a few that were useless 6 in the same board in fact ranging from 31mA to 33mA, have been using the cal for the time being but tbh I enjoy carrying out the Zs test, maybe strange but it gives me extra peace of mind that everything is as sholud be!