reply to Caddyroger
Re: 2 different amp size breakers on one circuit You mean your breaker panel is supplying the furnace with 1x 60A and 1x 30A, while the breakers on the furnace receiving those circuits are 2x 60A?
Well that would be your problem right? The furnace needs 2x 60A and draws too much power for the 30A breaker in your panel.
You'll need to replace the 30A with a 60A breaker and replace the 10AWG wire with 6AWG.
Make sure the two 60A breakers in your panel are on different legs.