Square peg round hole.......

[Michaelwgroves]

I'm looking at running 25mm SWA to supply secondary CU to future proof HMO design. See my previous threads for details House of Multiple Occupancy Design - https://www.electriciansforums.co.uk/threads/house-of-multiple-occupancy-design.124817/

My issue is a 100A CU and SP Distribution boards seem to only have 16mm neutral terminals from what I can find. So I'm stuck, can you buy bigger terminals, if not what about placing Henley block in CU/SP Distribution board to run main neutrals. At the risk of being scalded, dare I say drill out to accommodate 25mm ?
Otherwise only solution would be to buy 3Phase which seems like massive overkill for what I'm looking to do.

 

[Pete999]

I'm looking at running 25mm SWA to supply secondary CU to future proof HMO design. See my previous threads for details House of Multiple Occupancy Design - https://www.electriciansforums.co.uk/threads/house-of-multiple-occupancy-design.124817/

My issue is a 100A CU and SP Distribution boards seem to only have 16mm neutral terminals from what I can find. So I'm stuck, can you buy bigger terminals, if not what about placing Henley block in CU/SP Distribution board to run main neutrals. At the risk of being scalded, dare I say drill out to accommodate 25mm ?
Otherwise only solution would be to buy 3Phase which seems like massive overkill for what I'm looking to do.

May seem daft, but why 25mm2SWA? without being rude or condescending have any cable calculations been done? What is the distance of the cable run? what method of install? you say 100A but that is the rating of the CU.

 

[Michaelwgroves]

Pete, take a look at my HMO post, it'll them make sense. I didn't want other post to get distracted.

 

[Pete999]

Pete, take a look at my HMO post, it'll them make sense. I didn't want other post to get distracted.

Just seen it

 

[Pete999]

Pete, take a look at my HMO post, it'll them make sense. I didn't want other post to get distracted.

Still can't get my head around it Micheal, you must have calculated the Max Demand, it can be a lot lower than you may think, as already said in your previous post

 

[Leesparkykent]

Taking a distribution circuit from the CU is poor design as it will not achieve discrimination. If you insist on doing it then you could use a 25mm to 16mm reducing pin.

Un-insulated Reducing Pin - SWA - http://www.swaonline.co.uk/cable-terminations/copper-pin-terminals/uninsulated-reducing-pin

 

[123]

No Electric Showers, Hob is gas...why do you need 25mm?
Why take the SWA to a consumer unit, it's not a good setup to have a sub board fed from an MCB imo.

 

[Michaelwgroves]

All fair comments, which I tend to agree, but better suited to HMO thread.

Can I use a reducing pin, does that not reduce down to 16mm capacity,although at the point I need 25mm I can simply cut it off. But that only works in CU, if I use SP Distributionim from outset I’m still restricted to 16mm?

 

[Leesparkykent]

All fair comments, which I tend to agree, but better suited to HMO thread.

Can I use a reducing pin, does that not reduce down to 16mm capacity,although at the point I need 25mm I can simply cut it off. But that only works in CU, if I use SP Distributionim from outset I’m still restricted to 16mm?

The max size OCPD device is going to be 63A if your using 60898's...The CCC of 16mm SWA is above that anyway...I assumed you selected 25mm for voltdrop.

 

[westward10]

I would never consider running 16.0 swa final circuits from a consumer unit let alone 25.0, forgetting discrimination it is a bad idea. You need a more substantial board if you go down this route with BS88 fuses or 947-2 devices.

 

[Leesparkykent]

I would never consider running 16.0 swa final circuits from a consumer unit let alone 25.0, forgetting discrimination it is a bad idea. You need a more substantial board if you go down this route with BS88 fuses or 947-2 devices.

Exactly my thoughts.

 

[westward10]

You would have to be a pretty slick cable dresser to form 16.0 or 25.0 conductors which are xlpe insulated so they were not placing undue stress on terminations and the devices, impossible I would say. That is assuming the devices fit once you have made off all the cables to the enclosure.

 

[ipf]

You would have to be a pretty slick cable dresser to form 16.0 or 25.0 conductors which are xlpe insulated so they were not placing undue stress on terminations and the devices, impossible I would say. That is assuming the devices fit once you have made off all the cables to the enclosure.

Yes. It would be a case of individual switched fuses, or equivalent, local to supply position for me. If cost is the main factor, there could be problems doing things by the book...but, that's how it should be, imo.
Is a 100amp single phase suitable? A 3 phase supply would solve a lot of problems.

 

[Strima]

Yes. It would be a case of individual switched fuses, or equivalent, local to supply position for me. If cost is the main factor, there could be problems doing things by the book...but, that's how it should be, imo.
Is a 100amp single phase suitable? A 3 phase supply would solve a lot of problems.

There's a lot of single phase circuits that are a bugger to balance which suppliers don't like and tend to charge the customer more money for.

 

[123]

With no Electric Showers, Heating, or Hob...not sure why 3 Phase would be needed?