"new granny flat"

[mdgibbs32]

Hi All
I have been asked to look into putting in a CU in a garage that is likely to be converted into a granny flat in the near future. Planning on using 10mm or 16mm SWA cable (buried to 600mm) as no real idea what load is going to be if it is converted so want to take worst case into consideration. Owner has said he is going to install gas heating but i cant guarantee that, or what shower is going to be used etc etc.
Plan on installing a small split load CU in garage but cant make my mind up whether to attache to existing CU in house or whether to split into the tails via henley block. All experianced advice gratefull received. Thanks

 

[Engineer54]

Depends on what the present supply in the house can safety allocate to this future granny flat. i can't see you needing more than a 10mm supply cable. i can't see a granny needing more than a 8KW shower, if gas isn't used for heating and water. Nothing stopping you in the first instance taking the supply from the existing CU for garage purposes, which can be changed to Henley blocks at a later date...

 

[MDJ]

Hi All
I have been asked to look into putting in a CU in a garage that is likely to be converted into a granny flat in the near future. Planning on using 10mm or 16mm SWA cable (buried to 600mm) as no real idea what load is going to be if it is converted so want to take worst case into consideration. Owner has said he is going to install gas heating but i cant guarantee that, or what shower is going to be used etc etc.
Plan on installing a small split load CU in garage but cant make my mind up whether to attache to existing CU in house or whether to split into the tails via henley block. All experianced advice gratefull received. Thanks

if you do split the supply with the tails from henley blocks to the main consumer unit rather than feed the new dist board to the granny flat from the existing DB, don't forget you need to add a main switch, you need 1 main switch to isolate everything, and IMO for what it's worth here I would suggest a 10mm2 3 core armoured, I doubt a 16mm2 would be required for an area that small considering gas heating will be used, JMO.

 

[mdgibbs32]

thanks guys, sometime i overthink things and then cant decide best rout to go when in reality both are right lol
much appreciated

 

[sparks1973]

Depends on what the present supply in the house can safety allocate to this future granny flat. i can't see you needing more than a 10mm supply cable. i can't see a granny needing more than a 8KW shower, if gas isn't used for heating and water. Nothing stopping you in the first instance taking the supply from the existing CU for garage purposes, which can be changed to Henley blocks at a later date...

i`d go for a 16mmCSA...and give em 60A....(depending on all the usualls of course..VD etc)....

 

[Engineer54]

i`d go for a 16mmCSA...and give em 60A....(depending on all the usualls of course..VD etc)....

Jesus, ....what are you expecting in this maybe granny flat/come garage to warrant a 60A supply?? The main house will probably only have an 80A to start with... lol!!

 

[sparks1973]

Jesus, ....what are you expecting in this maybe granny flat/come garage to warrant a 60A supply?? The main house will probably only have an 80A to start with... lol!!

dont get me wrong here eng...i understand the issue you may have....
but you can protect the 16mm csa sub with 60A opd...you aint gonna get blowing bullits as you quite rightly say it will never get there......but use the fuse to protect the cable.....

 

[Engineer54]

dont get me wrong here eng...i understand the issue you may have....
but you can protect the 16mm csa sub with 60A opd...you aint gonna get blowing bullits as you quite rightly say it will never get there......but use the fuse to protect the cable.....

Sorry, i just don't understand your reasoning for a 16mm sub on a 60A supply for at best a granny flat.

 

[sparks1973]

i understand it may seem extreem....and as the O/P has stated it may be that a 10mmCSA is adequate...theres a few `maybe`s` goin on here...such as the KW rating of shower.....and the choice of leccy...or gas for water heating....

 

[sparks1973]

don`t forget the max usage will be dictated by the bullet at the source head....together with expected usage...and design current for finals....

 

[Engineer54]

i understand it may seem extreem....and as the O/P has stated it may be that a 10mmCSA is adequate...theres a few `maybe`s` goin on here...such as the KW rating of shower.....and the choice of leccy...or gas for water heating....

Unless this garage is a good distance away from the main house, it just isn't going to warrant a 16mm cable and certainly not 60A supply. You'll be lucky to see 40A being drawn on a normal family 2 bed house 99% of the time, so for such a small area, for one person, It'll just be a total waste of time, hassle and money....