Hi. I have an Arcoaire electric furnace, model no. MF20N2600A. It runs for about a minute, maybe less, and then trips the breaker. The unit itself has a 50a breaker. Then it runs to a box on the wall with a 40a breaker. At the main fuse panel it is controlled by a 100a breaker. It is the 100a at the main panel that is tripping. I thought it was odd that the 100a trips but the others don't. So maybe the breaker was bad. I replaced it with a spare 50a that I had lying around and it still trips at the main fuse panel. Are there any things a DIYer with a multimeter can troubleshoot here, or is it time to call an HVAC repairman? Thanks Curt Edit: Forgot to mention that I've already changed the filter.