I have a new stelpro electric heater 240v to install. The wall wire is also a 240v, it has been tested. 2 blacks wires and a green one are coming from the heater. The wire from the wall has only one black one white and one green wire. The heater green wire goes with the green wall wire (ground). What about the rest of the wires? Thanks
They don't make cables with black/black/green
Since /2 cables do not come in black/black/green as a color combination, and running neutral to a heater that will never need it is rather pointless anyway, the previous installer ran a regular /2 cable (black/white/green) and used the black and white as the two hots.
So, with the power off, connect one heater black to the black from the wall, the other heater black to the white from the wall, and the greens together and to a box grounding pigtail if the box is metal. While you're in there, put a wrap of black electrical tape on the white wire from the wall to mark it as a hot and save the next installer the trouble.