It is in your best interest to replace the Zinsco panel. Those breakers have a very common habit of not tripping on overload which tends to cause extreme overheating (fire).

I agree with the other coment. If at all possible the panel should be replaced. These panels have several problems with them.

1) The breakers are very unreliable. I have personal expierience with many overloaded circuits (25-30 amps on a 20 amp breaker) that did not trip. I also had a guy cut across a 240v heater wire (that he thought was off) and blew up his wire cutters. He called us out to check out the problem because the breaker did not trip. I found the breaker still on after he had caused a major short circuit!

2) I have many pictures of Zinsco/Sylvania panel damage. The breakers burn up at the connection to the bussing. If anyone would like a copy of some pictures, or copies of some of the personal expieriences with these breakers you can email me at mrelectricoly@msn.com.

PS: you can add a ground bar (as long as ther is room) and relocate the ground wires to it so you have room in the neutral bar for more neutral wires.

PSS: If you are not confortable with this please call a licensed electrican.

Jim Simmons
WA State Master Electrician