In article , indago wrote:

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

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...

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

You mean 12 gauge / 20 amp, of course.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.