My central heating unit trips one set of circuit breakers, I've notice that the heating elements each have two sets of breakers, one set of breakers is a 50 amp. The other is a 40 amp. When the heater comes on both heating elements come on and it starts heating the house, about 5 to 10 minutes later the 40 amp. Breaker trips, it takes longer to heat the house but the heater does go off after a while depending how cold it is, I always keep the thermostat at 70, should I replace the 40 amp. Breaker with a 50 amp. Or is there something else that is causing that breaker to trip.

Never increase breaker size above the one designed for the equipment and installed at the factory.

It is possible one of the heaters is saging making contact with another heater causeing the problem

It is possible that you have a weak circuit breaker and a weak one will trip easier.

It is possible that the wiring connections at the breaker or main electric panel are loose allowing a over current condition which will trip the breaker also from the breaker overheating.

There are many posibilities and sorry to say you need a Amprobe meter to start any of the electric tests. You may be able to check the setup for loose wiring but if you do not know what you are doing it is best to leave it to a on site professional.

Merry Christmas