Unbalanced Delta Heater Circuit

It has been a long time since I have had to figure this calculation, so maybe someone could refresh my memory. I am hooking up some single phase heaters to a three phase source. The line current was easy enough to figure if all three phases are equal, ie. A-B=10A B-C=10A A-C=10A then line current is ~17.3A on each line.

What if I add a fourth heater to one phase (A-B=10A, B-C=10A, and A-C=20A) what would be the resulting currents in each line A,B, and C? I know B would stay the same but how do I calculate the increase in A and C. If I was to simply add the 10A to each line the the value would be 27.3, but if I average the current into the node then multiply by 1.73 the current is 25.98. Or is there another way to calculate it that I haven't though about?

I am feeding these heaters from a 30A breaker, so I know I could only add one extra heater if my estimates are right. I don't plan on adding one, just trying to figure out if I could.

Thanks Guys

Here's my analysis:

Damn, I knew I would have to resort to Trig . It does make sense though, just been awhile since I have done those kind of calculations.

Thanks for the analysis.

I would ask your engineering department.
you could post this question on an electrical website www.mikeholt.com

it's been way to long for me to answer.

regards,
james