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Advice Please - Mains cartridge fused Isolator switch or MCB and isolator Switch.
Former Community Member
I manage a residential mobile home park with homes that individually have mains supply TT coming to a meter box recessed into a breeze block shed. The tails then come from the meter into the shed and into an old style bakelite rewireable 40a fused isolator switch. There is then an outgoing 10mm SWA cable running from the isolator switch underground from the shed to the home and then into the consumer unit for the home (total run approx. 8 to 10 metres). Having had an EICR for one of the homes I have been adviced that these isolator switches will need to be replaced as the swa cable is not properly terminated (it is not glanded in to the isolator switch and the wire stranded sheathing is twisted together and connected to the earth block.) My question is can this isolator switch be replaced with an 18th edition 3 way metal enclosure with double pole isolator switch and 40a mcb or should it be replaced with a 60a (or 40a) cartridge fused double poled mains isolator switch. Additionally would it a be a good idea to put a 60a RCD into the shed and either use a five way enclosure (in place of 3 way enclosure) or a 2 way enclosure fed from the cartridge isolator switch. All the homes have a standard consumer unit containing either a 60a or 80a RCD and 3 to 5 suitable MCB's (32a, 16a, 6a).
The original description of this installation is not very clear and complete. On the sites near to me I have observed caravan or residential homes connected via a local "hook up point". The hook up point comprises a 30 mA R.C.D. and a meter and M.C.B., plus a 16 Amp blue socket. These points are normally rated at 16 Amps, but recently the site owners have been de-rating them to B10 M.C.B.s at the hook up point. The submain supplying these can be TN-C-S. but at the hook up point this is converted to TT, the C.P.C. not being continuous into the caravan or residential home. With the caravan or residential home there may be a conventional consumer unit with 32 Amp M.C.B.s for ring finals or showers or cookers etc. These are installed by the makers not realizing that reduced current supplies may be available. The owners soon realise just what can and can not be used together. The Consumer unit is fitted with an R.C.D at 30mA sensitivity. The caravan earthing is TT and an earth rod is installed at the hook up point.
I like that idea that two R.C.D.s protect the installation.
Of course this permanent residence mentioned in the O.P. may be considered to be a permanent home and be supplied directly by a submain. In which case P.M.E. earthing may be possible and will comply. 708.411.4
The original description of this installation is not very clear and complete. On the sites near to me I have observed caravan or residential homes connected via a local "hook up point". The hook up point comprises a 30 mA R.C.D. and a meter and M.C.B., plus a 16 Amp blue socket. These points are normally rated at 16 Amps, but recently the site owners have been de-rating them to B10 M.C.B.s at the hook up point. The submain supplying these can be TN-C-S. but at the hook up point this is converted to TT, the C.P.C. not being continuous into the caravan or residential home. With the caravan or residential home there may be a conventional consumer unit with 32 Amp M.C.B.s for ring finals or showers or cookers etc. These are installed by the makers not realizing that reduced current supplies may be available. The owners soon realise just what can and can not be used together. The Consumer unit is fitted with an R.C.D at 30mA sensitivity. The caravan earthing is TT and an earth rod is installed at the hook up point.
I like that idea that two R.C.D.s protect the installation.
Of course this permanent residence mentioned in the O.P. may be considered to be a permanent home and be supplied directly by a submain. In which case P.M.E. earthing may be possible and will comply. 708.411.4
