Supply to con unit?

[ian t]

Hello to all,
Could do with a spot of advice please.

Is it acceptable to utilise an existing 6mm T&E cable to supply a second consumer unit to be located in an extension, comprising a utility room and a wet room. The new con unit (clients requested) will supply a couple of double sockets, 3 lighting points, an outside socket, underfloor heating (11amps peak load) and a 24v transformer for a shower pump. The 6mm T&E is supplied from a 32amp MCB on the RCD side of existing con unit, and tests ok The second con unit will have split rcd protection (17th edition)
Are ther any implications to having 2 rcd's in line, one for 6mm cable and one for the final cicuit?

Thanks in advance

 

[Spudnik]

Not a good idea to have two 30ma rcd's in line.

Therefore the second location could be supplied from its existing RCD protected way and have a standard board with no rcd to achieve discrimination.

32Amp should be ok however, it is up to you to ensure that the supply will meet demand, being a utility room and wet room.

If its doable, i would try and get a 10mm in there with a 40A upfront.

IMHO.

 

[sivoodoo]

just out of interest, what would be the implications of two rcd's in line?
cheers.

 

[Spudnik]

just out of interest, what would be the implications of two rcd's in line?
cheers.

There would be no discrimination between the 2 30Ma's RCD's.

Im sure there is a reg about it somewhere but dont have my BRB to hand at the mo!

 

[mrloy99]

just out of interest, what would be the implications of two rcd's in line?
cheers.

your one at the main cons unit could be typeS time dalayed

 

[Guest123]

your one at the main cons unit could be typeS time dalayed

Depending on how the 6mm T+E sub-main was installed i.e, if at a depth of less than 50mm from the surface of the wall then and not in earthed metallic conduit, it would need 30mA protection. If surface run in it's entireity in trunking/conduit and labelled etc then TD RCD would be ok.

 

[mrloy99]

Depending on how the 6mm T+E sub-main was installed i.e, if at a depth of less than 50mm from the surface of the wall then and not in earthed metallic conduit, it would need 30mA protection. If surface run in it's entireity in trunking/conduit and labelled etc then TD RCD would be ok.

wot,can you not get 30ma with a time delay?

 

[Guest123]

wot,can you not get 30ma with a time delay?

Well I have to say I've never come across one. Also It would not comply with regs for personal protection being TD. But that all depends on how he installs the sub-main.

 

[mrloy99]

Well I have to say I've never come across one. Also It would not comply with regs for personal protection being TD. But that all depends on how he installs the sub-main.

nor have I,
best to go for one at the main cons unit then.

 

[ian t]

Thanks folks, i think the 6mm will need putting on a separate RCD so it doesn't effect the main house in the event of tripping, but only the extension. I presume that would comply with 314, installation circuit arrangements?