Doing a lot of EICRs at the moment and have came across what I'm sure is a common enough problem. In an off grid rural cottage I have a TT system, Diesel Generator that runs and charges batteries when they are below 10 percent or so.
Ra is about 150 Ohms... was about 3 ohms for Ze before main earth was disconnected from electrode.
Now table 53.1 tells me that a 500mA RCD would be acceptable in this instance, not that that would ever be the case as everything is protected by 30mA RCD albeit one main one for everything. ( An exception to this is the circuit from generator to Invertor IN circuit and Invertor OUT i don't believe is on an RCD. Invertor out is a 25A MCB which limits the entire supply which is a second 2 way DB in the shed that house the generator doing 2 sockets and then onto an 8 way main RCD board in the house.
My question is basically most mcbs 20 amp and above are failing max Zs readings ( In most instances not by much ).
Because it is a remote holiday let it has a very small amount of sockets and no kettle or any other appliances supplied and all heating cooking is gas/oil. I maybe have the luxury of sticking a couple of rings onto 10A mcbs in which case they pass but not sure if table 53.1 negates the need for this?
SO long as the RCD trips within 200ms can this be passed so long as deviations from BS7671 are noted?
Example readings are 16A MCB 2.5 Ohms which is 2.2 max and 32A MCB 3.5 Ohms which is 1.1 max. all other 6A circuits pass.
Appreciate advice as its not something i have dealt with too much over the years.
( Sorry for waffling on also cheers! )
Ra is about 150 Ohms... was about 3 ohms for Ze before main earth was disconnected from electrode.
Now table 53.1 tells me that a 500mA RCD would be acceptable in this instance, not that that would ever be the case as everything is protected by 30mA RCD albeit one main one for everything. ( An exception to this is the circuit from generator to Invertor IN circuit and Invertor OUT i don't believe is on an RCD. Invertor out is a 25A MCB which limits the entire supply which is a second 2 way DB in the shed that house the generator doing 2 sockets and then onto an 8 way main RCD board in the house.
My question is basically most mcbs 20 amp and above are failing max Zs readings ( In most instances not by much ).
Because it is a remote holiday let it has a very small amount of sockets and no kettle or any other appliances supplied and all heating cooking is gas/oil. I maybe have the luxury of sticking a couple of rings onto 10A mcbs in which case they pass but not sure if table 53.1 negates the need for this?
SO long as the RCD trips within 200ms can this be passed so long as deviations from BS7671 are noted?
Example readings are 16A MCB 2.5 Ohms which is 2.2 max and 32A MCB 3.5 Ohms which is 1.1 max. all other 6A circuits pass.
Appreciate advice as its not something i have dealt with too much over the years.
( Sorry for waffling on also cheers! )
