Post
by ericmark »
Wed May 07, 2008 1:41 pm
I will also point out Part P and think it would be unwise to try to complete this work as DIY but will try to answer your questions.
At this time RCD's of 30ma are only required on sockets which may be used outside and showers etc in bathrooms.
Depending on earthing arrangements RCD's of a size found by calculation may also be required.
From 1st July 2008 most items will need RCD protection and safety circuits i.e. lights will not be allowed to use same RCD as sockets and most houses will need at least three earth leakage devices very possible more.
It was considered unwise to run fixed heating appliances like ovens and hot plates from RCD's but under the new regulations these items will need re-wiring in special cable if they are not to be protected by an RCD. As a result I would say protect everything with an RCD.
As to which type either you can get three way split boards with two double pole RCD's and also room for some single pole RCBO's or you can fit RCBO's to every circuit (Except in caravans) the latter is preferred but expensive. Special RCD's are available for power tools etc where with a power cut they will trip so stopping drills etc restarting after a power cut and bouncing down the bench these are called Active most RCD's are passive that's where power cuts don't trip them there are also automatic resetting which will auto test the line and if clear try to reset three times but at nearly £300 each I think insurance on the freezer would be cheaper! Most RCD to protect personnel are ratted at 30 milliamp but sometimes for gardens etc we use 10 ma to avoid tripping the main one.
Once fitted they all must be tested at 50% rated valve to show they will not trip at 100% and must trip and at 500% and must trip in 40ms to measure this special meters will be required and together with the meters required for insulation resistance and to calculate volt drop earth loop impedance and prospective short circuit will cost around £750 here I will return to Part P if you follow the links and down load from page 23 it shows you the forms you need to fill in. If your in Scotland you don't have Part P you have another set of regs which are even harder to comply with even requiring building control to sink a socket in the wall.
Is there anything you should know. Well passing C&G 2391 and C&G 2382 would be a good start most electricians can learn what is required in about 6 months study where they originally started in the days only an apprenticeship was required. I have know others get through Radio Hams etc. But unless you have some formal electrical training before you start I would not expect to pass.
