Aenuff wrote:

10 heaters, 3 x 3.4Kw + 7 x 1.7Kw spread across 4, possibly 5 - need to
double check, separate rings. No more than 2 x 1.7 and 2 x 3.4s on any one
ring. The building is three phase. We can get economy 7 but no budget for 2
years by which time there should be a budget for an oil fired zoned system
with a couple of boilers covering the 2 main halves of the building.

Even 2 x 1.7 and 2 x 3.4 is marginal:-

Total of 10.2 kW, at 230 volts that's 44 amps, much too much for a
ring circuit.

Even 2 x 3.4 kW is 29.5 amps leaving very little for anything else.

--
Chris Green