Supply requirement for heaters

I urge not calculating with too much precision. If the heater is designed 220 volts, and is connected to 250 volt supply, it will draw significantly more current then calculation suggests.

I urge the use of OCPD and cable rated for 125 amps. Also consider that the heater may be replaced with another of a similar NOMINAL rating, but slightly higher actual  loading, within the lifetime of the electrical installation.

Well the plot thickens! NGrid came out and discovered a brand new LUCY box with 3 x 200A fuses still in their packets ready to go. From this box there are 4 x meter tails in trunking which rises to the next floor. We had a look just before Xmas and found that they enter a metal enclosure equiped with 3 x CTs and associated wiring but with no meter fitted. The tails pass through this box into what was a brand new Square D I-Line Speed D Size I series B panel board equipped with MCCBs of various ratings and an incomer MCCB rated at 180A. NOTE: NGrid said that this supply wasn't even on their asset list and they had no idea it had been put in. My guess at the date of installation is something like 1994.

This opens up a few more possibilities.

We can either, fit a 100A MCCB and run some 35mm 4 core SWA to a suitable outlet for the heater, or, we can go up to say, 50mm 4 core and uprate the MCCB to say 150A, then hang a 4 way TPN dist board at the other end, one way of which can be used for the heater. The latter proposition in terms of costs going forward looks to be more attractive because there is a proposal in the offing to also fit a lift, and a supply will be needed for that, which brings me onto my next question about requirements for lift supplies in general which I will post seperately in another thread.

Well the plot thickens! NGrid came out and discovered a brand new LUCY box with 3 x 200A fuses still in their packets ready to go. From this box there are 4 x meter tails in trunking which rises to the next floor. We had a look just before Xmas and found that they enter a metal enclosure equiped with 3 x CTs and associated wiring but with no meter fitted. The tails pass through this box into what was a brand new Square D I-Line Speed D Size I series B panel board equipped with MCCBs of various ratings and an incomer MCCB rated at 180A. NOTE: NGrid said that this supply wasn't even on their asset list and they had no idea it had been put in. My guess at the date of installation is something like 1994.

This opens up a few more possibilities.

We can either, fit a 100A MCCB and run some 35mm 4 core SWA to a suitable outlet for the heater, or, we can go up to say, 50mm 4 core and uprate the MCCB to say 150A, then hang a 4 way TPN dist board at the other end, one way of which can be used for the heater. The latter proposition in terms of costs going forward looks to be more attractive because there is a proposal in the offing to also fit a lift, and a supply will be needed for that, which brings me onto my next question about requirements for lift supplies in general which I will post seperately in another thread.