I'm pricing out a job for a local plant. They had a gas heater go out and they are wanting to replace it with an electric heater to seee if there are any savings.

They are installing three sets of two 25kw heaters(480v). This is 60.1 amps per set. This is for 1 machine with the pontential of adding 5 more.

I'm feeding them from a busbar to a breaker panel to the heaters. I'm going to size my wire according to this number #6THHN.

Do I need to size my wire feeding the breakers at 180 amps or can I derate?

If I add another machine am I then up to 360 amps? Or five machines and 1080amps?

Thanks for your expertise.

I don't see any reason why you could use anything less than 100% of connected load and if this is continuous load it would be 125%.

Thanks Greg, I was going the wrong way with my size.