ECN Forum Forums Code Related Discussion Canadian Electrical Code Topics #37 marrette only up to 300v?

On friday I had to make a joint with four 12awg wires (347v) so I asked my apprentice to get me a #37. He tells me they're only good for up to 300volts. "Who told you that" I say. "It says so right on the box" he says.
Don't you hate it when the apprentice is right