061208 1139 - 46erjoe posted:

I need to install baseboard electric heating units in two rooms I'm
refurbishing. One will need a 48" 2000 watt unit; the other a 36" 1500
watt unit.

The instructions in each box say that I will need to use a 220v
circuit with "amperage according to local code".

Both rooms are next to each other and I'm wondering if instead of
fishing two wires, I can go with one 10/2 30amp circuit and have both
units branching off the main line. What might be the minimum wiring
and amp circuit? What would be safest? What's the most amperage I can
get out of a 10/2 line?

Related question: I've got tons of 12/3 wiring with ground laying
around unused. Can I turn this into, say, 10/2 by simply clamping
the black and red wires together at the panel and at the end point and
then painting the red wire with black marker pen to indicate power? I
hate to waste wire with the cost of copper these days.

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Derating the 20 gauge wire to 80% would be 16 Amps.

Don't even think about paralleling the wiring. If the voltage drop is
severe, then consider running two of the 3-wire cables -- one for each
heater.