The unit trips the breaker. It doesn't do it all the time, but more then not. The specs on the back of the unit state min/max 45/60 amp. The old unit only used a 30 amp. Can I replace the 30 amp with a 45/50 amp without burning down the house or causing other electircal issues?

So are you saying the old unit was replaced but the wiring was not??

If the new unit calls for a 45A breaker minimum what wold posses the installer to keep the 30??

You need to tell us the "Minimum circuit ampacity" and the "Maximum fuse or breaker size".

Not "min/max, 45/60". Be specific.

If the minimum circuit ampacity really is 45 amps then a strong NO, you cannot simply increase the breaker size. You MUST run a new circuit.
While you're at it find another A/C guy.

A pair of #6's, and 10 for ground would work on 50 or 60 Amp Breaker.
If it was 30 Amps, wiring may need upgrading. Don't put On a Breaker larger than the wire can handle.
If existing wiring was #6, you Lucked out.