Minimum values of insulation resistance

Extract from the old forum...


Keith,


As I'm sure you're well aware , it is a requirement of BS7671 that any socket outlet that may be used for portable equipment outdoors to be protected by a 30mA RCD, I interpret this as all sockets on the ground floor of a building. What you describe sounds unusual, I would suspect that the leakage current of the connected equipment is too high & therefore causing nuisance tripping.


Electricity Supply Regulation 26 indicates that the level of earth leakage current should not normally exceed one ten thousandth part of the installation maximum demand (for example, 10 mA earth leakage current for an installation with a maximum demand of 100 A). Data processing equipment is likely to have a higher leakage current than this, so special regulations become necessary. Foremost is the requirement that where earthing is used for functional purposes (to allow the filters to do their job) as well as protective purposes, the protective function must take precedence. When the earth leakage current is high, serious shocks are likely from accessible conductive parts which are connected to a protective conductor which is not itself solidly connected to the main earth terminal.


Where an installation having more than one item of stationary equipment with earth leakage current exceeding 3.5 mA is protected by an RCD the sum of the earth leakage currents due to data processing equipment must not exceed 25% of the device tripping current.


It would be interesting to know what the actual measured earth leakage current was on each cct & did the RCBO's pass the 15mA test with the load disconected?


Regards,


Alan


ahr35181


Posts: 492

Joined: 18 January 2003

 

Extract from the old forum...


Keith,


As I'm sure you're well aware , it is a requirement of BS7671 that any socket outlet that may be used for portable equipment outdoors to be protected by a 30mA RCD, I interpret this as all sockets on the ground floor of a building. What you describe sounds unusual, I would suspect that the leakage current of the connected equipment is too high & therefore causing nuisance tripping.


Electricity Supply Regulation 26 indicates that the level of earth leakage current should not normally exceed one ten thousandth part of the installation maximum demand (for example, 10 mA earth leakage current for an installation with a maximum demand of 100 A). Data processing equipment is likely to have a higher leakage current than this, so special regulations become necessary. Foremost is the requirement that where earthing is used for functional purposes (to allow the filters to do their job) as well as protective purposes, the protective function must take precedence. When the earth leakage current is high, serious shocks are likely from accessible conductive parts which are connected to a protective conductor which is not itself solidly connected to the main earth terminal.


Where an installation having more than one item of stationary equipment with earth leakage current exceeding 3.5 mA is protected by an RCD the sum of the earth leakage currents due to data processing equipment must not exceed 25% of the device tripping current.


It would be interesting to know what the actual measured earth leakage current was on each cct & did the RCBO's pass the 15mA test with the load disconected?


Regards,


Alan


ahr35181


Posts: 492

Joined: 18 January 2003