Various electrial questions

Piers Finlayson · 2010-02-28T18:16:44+00:00

I'm contemplating a serious rewire/CU replacement and had a few questions:- I'll be using SWA to feed the CU some distance from the incoming supply. I've read the excellent terminating SWA article on the wiki, but it is unclear about exactly what size SWA can be cut using bolt croppers. I'll probably be using 10mm2 or 16mm2 SWA - is it reasonable to expect bolt croppers to be fine for cutting these sizes?- Is my supply TN-S or TN-C-S?While I have seperate PE and N entering my building, the PE and N are connect together on my property. I have two wires (11kV?) coming onto my property, which terminate on a larger transformer on a telegraph pole. I can see the PE is provided from underground at the pole, and is connected to the N supply from the transformer. So my thinking is that I'm TN-S if the transformer is considered the power source, but TN-C-S otherwise. Thoughts?(Yes, I have asked my electricity supplier, but they have suggested that I contact the DNO. I haven't yet summoned up the energy to do this.)- I'm considering using a metal CU. From doing a bit of research online it may be a requirement that the supply to this CU is protected by a 100mA time delayed RCD. However, I'm unclear as to whether this is only a requirement for TT systems or whether it's applicable to my scenario. I'll be digging out my 17th ed regs later, but can anyone let me know whether the RCD is a requirement here?- I'm considering a three phase CU, and using this as a single phase CU. I'm unfamiliar with the internal construction of these CUs - is there generally any problems with using a TP CU as a single phase one? (The main obvious issue I've seen is that for the model I'm looking at a DP incoming switch is not available - so I'd have to use a TP one and leave one pole unused.- Finally, any recommendations or brands to steer clear of? I've been looking at the Hager Invicta 3.Thanks,Piers

Feb 28, 2010 26 Replies

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John Rumm 16 years ago

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Still surprisingly expensive for something that can be assembled with a DIN enclosure and off the shelf parts. Still I suppose you do get plenty of wiring room in the pre built versions.

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ARWadsworth 16 years ago

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> Still surprisingly expensive for something that can be assembled with a

I have been fitting these

when needed. I pay around £20 from my wholesalers inc VAT. The 25mm tails go straight into the terminals with no bending required. I have found on line suppliers wanting £50+ for the same item.

Adam

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Piers Finlayson 16 years ago

Ah, OK. The SWA will be after the break before make switch for the genny, which in turn will be after this CU.

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John Rumm 16 years ago

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What sort of fuse do they take? Are the boxes available in other ratings?

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Tim Watts 16 years ago

John Rumm wibbled on Monday 01 March 2010 22:05

Often BS88, at least the ones I've come across. Not sure about that specific one but it's likely.

100A, 80A and 60A seem to be the standard ratings.

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ARWadsworth 16 years ago

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>>>>> Still surprisingly expensive for something that can be assembled with a

It comes with a HRC fuse. They do a 100A switch but it comes with an 80A fuse! I assume that it is to allow some diversity against a 100A supply fuse.

See page 4 of

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ARWadsworth 16 years ago

Additional info

It uses these fuses

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