Cable selection for granny flat supply

[sidekick]

Have been asked to use 10mm swa to supply Granny flat with following spec from mcb on house csu.
Think should really be 16mmswa from separate switch in house. Am I missing something.

22 down lightslus 2 outside lights
10 2g sockets and 1 2g outside socket
electric oven
electric hob
electric shower
x 2 extractors
x 2 smoke detectors
3kw water heater
and x 3 poss 4 electric panel heaters

Quite a lot for 10mmswa. will first check with DNO to see if additional supply required and if not will supply separate feed from house via separate isolation switch.

 

[Engineer54]

Almost sure TN-S but need to cut back of kitchen cupboard out to confirm on next visit.

Do WHAT??? ...lol!!

 

[sidekick]

Do WHAT??? ...lol!!

Afraid cupboards have been built in front of cut out.
Just hole showing meter. Could just get torch to shine down and see what looks like TN-S. What fun lol

 

[Engineer54]

Afraid cupboards have been built in front of cut out.
Just hole showing meter. Could just get torch to shine down and see what looks like TN-S. What fun lol

Surprised the meter reader didn't report that situation back to the DNO. How bloody ridiculous is that?? Shame the DNO hadn't been round to fit an update meter or whatever, they would have just put a hammer to the back of the cabinet, ...end of!! lol!!

 

[sidekick]

further to the load requirements of proposed granny flat. Following site visit I found proposed granny flat is 50m from summer house which is itself 25m fro main house.
Therefore, 10mm swa is no good for job. 16mm only allows 14kw current load of 60a before voltage drop puts it outside allowance.
so my question is, dos this Granny flat need its own new supply.

 

[davesparks]

Surprised the meter reader didn't report that situation back to the DNO. How bloody ridiculous is that?? Shame the DNO hadn't been round to fit an update meter or whatever, they would have just put a hammer to the back of the cabinet, ...end of!! lol!!

Lol, you clearly haven't met the modern meter readers! It's a miracle they can manage to find the front door! But more often than not you have to read your own meter and argue the ---- over your estimated bill.

And I think most meter fitters would have just walked away from it and told the boss there was no one home to let them in.

Its ridiculous! It will only get noticed when someone like us has to call the DNO in to fix a fault.

 

[NickD]

Following site visit I found proposed granny flat is 50m from summer house which is itself 25m fro main house.

Guess they don't like Granny much.

 

[Engineer54]

further to the load requirements of proposed granny flat. Following site visit I found proposed granny flat is 50m from summer house which is itself 25m fro main house.
Therefore, 10mm swa is no good for job. 16mm only allows 14kw current load of 60a before voltage drop puts it outside allowance.
so my question is, dos this Granny flat need its own new supply.

And a very good reason why you should never assume anything, until you have seen the job first hand yourself!! So you are now talking about what, a 75m run for the sub-main, may be a little less if a shorter route from the main house is possible?? Think this customer is going to have to dig a little deeper into his pocket to accommodate this installation...lol!!

 

[Octopus]

Give them a price for doing it properly and walk away, they are bound to find a cowboy who will bodge it for them!

 

[GLENNSPARK]

whats the length of run from origin of supply for this feeder?

edit:

sorry...just read some other posts stating this...

 

[GLENNSPARK]

further to the load requirements of proposed granny flat. Following site visit I found proposed granny flat is 50m from summer house which is itself 25m fro main house.
Therefore, 10mm swa is no good for job. 16mm only allows 14kw current load of 60a before voltage drop puts it outside allowance.
so my question is, dos this Granny need its own new supply.

well....if she keeps chuckin cash about like this one...she will:

 

[sidekick]

And a very good reason why you should never assume anything, until you have seen the job first hand yourself!! So you are now talking about what, a 75m run for the sub-main, may be a little less if a shorter route from the main house is possible?? Think this customer is going to have to dig a little deeper into his pocket to accommodate this installation...lol!!

Thanks for that. Am I correct in advising them an additional supply is needed? Can't seem to find another solution. ie No cable selection seems to be adequate from main house.

 

[davesparks]

It is possible to select a suitable cable following the normal calculation process.
I think you mentioned an In of 80A and a distance of 75mtrs so just work from the volt drop to find a suitable cable.
Just don't be surprised when it works out a little bit bigger than 10mm!

 

[GLENNSPARK]

It is possible to select a suitable cable following the normal calculation process.
I think you mentioned an In of 80A and a distance of 75mtrs so just work from the volt drop to find a suitable cable.
Just don't be surprised when it works out a little bit bigger than 10mm!

50mm.....

 

[GLENNSPARK]

if he drops his I B down to 60A...then a 35mm will cut it...

 

[Simonslimline]

1.35 x 60 x 75 Gives an AVD of 6.075 volts. Whithin the 3% allowed.

3 core 35mm2 SWA .