High Ze - DNO added an RCD!

IQ Electrical · Apr 4, 2011

ESQCR doesn't actually specify any max Ze values, the values are broad targets from an 'engineering agreement'.

Amazingly, there is no 'regulation' to force a DNO to comply with the 'engineering agreement' values!

Chr!s · Apr 4, 2011

I cant actually believe this, the ESQCR requires the DNO to maintain the Ze below the maximum of 0.35 for 100a TN-C-S system if they are supply the earth facility

ESQCR mentions no max figures for tncs

This can not be acceptable as a permanent solution, if it was my job I would kick up a fuss about it and if nothing was done have their rcd removed and fit an s type 100ma as my main switch

Not too much you can do about, you could TT it.

Is it an S type RCD? they have fitted?
If not why bother to fit the 17th edition split ccu`s as there is now no dicrimination with the supply
Are they going to pop around once a quarter and press the test button on their rcd

The ESQCR requires equipment of the dno and suppliers to ensure their equipments meets BS 7671, so an s type would ensure this.
If you have a 100 fuse and your ZE is 0.55 ohms this may be down to network parameters, but this wouldn't comply with BS7671, so they stick an rcd in to comply