3phase tt supply setup

[Lee321]

anyone got any ideas on how to arrange it?

in regards to the mains. i.e after the meter and before final circuits

need rcd and i see a challenge (yes its a searching question)

consideration of demand and cable sizes and ratings not needed at this stage although i will say its typical and under 100amp supply

 

[M107]

Meter > TP rcd in insulated enclosure > DB

 

[Andy™]

[quote name='Lee

 

[Lee321]

thats what i was bothered about. pvc enclosure + 3ph rcd's readily available or needing to make bespoke enclosure?

 

[Sidewinder]

Exactly as you would a 1ph but using 3ph gear instead.

 

[Lee321]

thx's again chaps fast replies.

yes side but are pvc enclosure with 3ph equipment in mind readily available?

 

[steptoe]

sorry guys,

wont it need a 4p RCD?

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[quote name='Lee

 

[Sidewinder]

Yes polymer enclosures for 3ph gear are readily available.

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Oh & Steps, yes a 4p RCD is what I said in my post.

 

[Electroglow]

I always use a 4 pole rcd on any earthing system... Makes more sense

 

[M107]

Where I posted TP that was supposed to indicate three phase rcd as in a 4 pole rcd...........Sorry or the confusion.

 

[Lee321]

its the enclosure that matters adds to cost as it could have been incorporated as the incomer on 3 ph db but you know whats next

 

[Electroglow]

Or is metal install a rcd before the dist board

 

[Lee321]

sorry glow not understanding that?

edit got it.

thats my point, adds to the cost/foot print, as far as i know all 3ph db's are metal

 

[Electroglow]

Incoming supply > rcd > in to dist board

100ma then 30ma or ppl may say different..

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It's a cost they have to pay to bewith in regulation I'm affraid lol

 

[Lee321]

yes mate thats what i wanted to avoid.

 

[NozSpark]

IIRC you don't "have" to RCD the tails so long as they pass through an insulating gland (not grommet strip) or insulating gland plate,

But your final circuits are more than likely to require RCD protection anyway

 

[Lee321]

you cant protect the casing though noz! ???

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you could triple insulate by adding sleeving for bolt and braces but just not allowed

 

[NozSpark]

You're not protecting the casing, you're protecting the tails

 

[Lee321]

hmmm not a prevention of the case becoming live then? so what is doing that?

prevents fire too

 

[Sidewinder]

Wow now, not all TT systems must have an RCD.

There are exceptions.

You also MUST be careful as to the loads you connect to them.

I have been working today on a site which if it were TT could never run as the loads would immediately trip a 30mA rcd.

What is your Ra on the install?

What is your earth electrode?