Connecting Multiple Bemco/Ryefield Boards

To add a twist, they are all being fitted with 24kW 3-phase electric water heaters

Presumably this is the equivalent of an electric combi-boiler, and instant hot water, no storage needed ? Such things are seen on the continent,  I have looked at a few installations like that in Berlin in the early 2000s.


If  it is not also being used for radiators then the BS7671 style diversity assumptions will tend to oversize the combined supplies, as in reality not all flats will run a bath at once (though if it

was supplying radiators you find that will all experience winter at the same time of year. ?)

Equally how many KW of heating are there ?


Still at rather more than 32A per phase just for water, you now need to give each flat at least a 45A 3 phase feed,  maybe 60, which is indeed going to eat up the ways in the Ryfield, but in reality not load them to anything like capacity for much of the time. I think you are going to have to try to get SPEN on-side if you can, as this is clearly going to look a bit odd.


It may be worth thinking about  taking  3 phases to the cooker point (I assume no gas ?)  as  per continental practice,  or you will probably need 100 A fuses per flat, most modern  hobs and so forth have options for splitting the load over more than 1 phase, but I can imagine the fitters from Currys looking a bit non-plussed, given how hard they make it to reconnect just 3 wires.

 

To add a twist, they are all being fitted with 24kW 3-phase electric water heaters

Presumably this is the equivalent of an electric combi-boiler, and instant hot water, no storage needed ? Such things are seen on the continent,  I have looked at a few installations like that in Berlin in the early 2000s.


If  it is not also being used for radiators then the BS7671 style diversity assumptions will tend to oversize the combined supplies, as in reality not all flats will run a bath at once (though if it

was supplying radiators you find that will all experience winter at the same time of year. ?)

Equally how many KW of heating are there ?


Still at rather more than 32A per phase just for water, you now need to give each flat at least a 45A 3 phase feed,  maybe 60, which is indeed going to eat up the ways in the Ryfield, but in reality not load them to anything like capacity for much of the time. I think you are going to have to try to get SPEN on-side if you can, as this is clearly going to look a bit odd.


It may be worth thinking about  taking  3 phases to the cooker point (I assume no gas ?)  as  per continental practice,  or you will probably need 100 A fuses per flat, most modern  hobs and so forth have options for splitting the load over more than 1 phase, but I can imagine the fitters from Currys looking a bit non-plussed, given how hard they make it to reconnect just 3 wires.