Supply to an annexe.

[Megaohm7]

I went to look at a job yesterday. It's an annexe that is joined to the house. The client requires a feed for an electric shower 8kw, a ring final,0 a lighting circuit, a feed for an under sink heater and a supply for a halogen hob. It's a granny annexe basically. There is a 16mm swa already in place and it terminates at the service head. my original thought was henley block the tails and switch fuse to protect the swa going into the annexe. The existing house supply is TNC-S and the main fuse is a 100a 1361 type 2. I know to allow for diversity but is still a considerable load to add to the main fuse on top of the existing installation.Any ideas would be greatly appreciated. :Neil

 

[Theorysparky]

whats the demand in the main house ???

 

[kme]

+1.

Need to know that, before you can determine what the proposed addition will do to the max. dem.

If acceptable, then the SWA sounds possible, dependant on length, and Zs (DB) at annexe end.

 

[Megaohm7]

Sorry chaps. The main house has 2 ring final circuits a shower circuit 8kw, 2 lighting circuits, immersion, and cooker circuit. so thats 3x 32a, 1x45a, 2x6a 1x16a.

---------- Post Auto-Merged at 18:35 ---------- Previous post was made at 18:34 ----------

Sorry chaps. The main house has 2 ring final circuits a shower circuit 8kw, 2 lighting circuits, immersion, and cooker circuit. so thats 3x 32a, 1x45a, 2x6a 1x16a.

10mtrs run on the swa..

 

[kme]

A second 8 KW shower; AND will be 3 rings plus cooker - thats a bit heavy. ; without doing the calcs.

 

[Theorysparky]

quick calcs would give worse case scenario for the main house as 60 amp

how many living in the main building ?????

 

[Sidewinder]

If the "Granny" is moving from main house to Annexe then same No. of peeps, but, the chance of duplicate showers & cookers.

Could be worth a punt as long as you make them fully aware of the possibilities of main fuse failure if they use the 2 showers & 2 cookers at the same time etc. etc.?

---------- Post Auto-Merged at 18:53 ---------- Previous post was made at 18:49 ----------

The other option is to use the criteria in Table 3.3 of the IEE "Electrical Installation Design Guide".

For individual dwellings 0.4x the total PERMANENT connected load.

i.e. NOT the socket outlets.

This is along the lines of the DNO calculations, but IIRC theirs is 0.35x TCL.

 

[Megaohm7]

There will be 2 people in the main house and it's the mother in law who will be in the annexe but at the moment she is in the house. so 3 people in all.

 

[Sidewinder]

Meg,

See above!

 

[batty]

Very unlikely they will blow 100 amp main fuse with just the three of them.

 

[Megaohm7]

I doubt it too now to be honest. That's what diversity is all about after all. Just want to be sure really.