Hi,

I was under the impression that 240 V devices used the neutral leg for 120 V to switches and other inputs that humans might touch and also for the internal blower fan. That is not the case here. Everything about this device is 240V. The picture below shows the schematic for this garage heater. I happen to have some 10 gauge 4 wire SOOW on hand. L1 will be black, L2 will be white and E will be green wire. I will fold the red wire back. Is this acceptable?

 

Most of the world doesn't have US style split-phase power, so there is no 120VAC unless its created inside the unit in most of the world.

 

For North America 240V, usually L1 and L2 are black and red wires. Insulate the white wire, not used or needed.
White is "neutral", which is not used in NA 240V circuits unless there is a split phase control, like you mention....

 

I happen to have some 10 gauge 4 wire SOOW on hand. L1 will be black, L2 will be white and E will be green wire. I will fold the red wire back. Is this acceptable?

AWG10 SOOW is good for 30A.

your load has current draw
5000W/240V = 20.83 A.

and the image shows document saying min AWG #10 is needed.
so as long as cable voltage rating is ok (300V or 600V), this is acceptable.

 

AWG10 SOOW is good for 30A.

your load has current draw
5000W/240V = 20.83 A.

To add to this; with a 10 gauge wire at 30A you should have a 30 amp breaker. 50 amps will not adequately protect the wiring if there's a short circuit.

 

yup...

 

I was under the impression that 240 V devices used the neutral leg for 120 V to switches and other inputs that humans might touch and also for the internal blower fan.

Sometimes. In many appliances (240V for US markets) there might be a timer, clock, light bulb, maybe a fan that lives from line to Neutral. It is very hard (years ago) to find a 240V light bulb. The timer in a dryer is often 120V.
I have repaired dryers where the timer and light bulb ran from Line to Ground. This will trip the GFI breakers in new houses.
There is some truth to what you say. I think when the US made appliances, they sometime used 120V fans in both 120 and 240 heaters to reduce the number of types of fans in stock. Because appliances are made for a worldwide market there are probably more 240V fans and very little 120V fans now.