150 panel in house. I want to run a 220 (sub-panel) feed to garage 25 feet away for 10,000 watt electric heater. There's room in the 150 panel. Would 60 amp breaker in the garage meet the 1.25 safety margin?
yes the 60-amp would meet the minimum requirement. In addition, please keep in mind that you need at least #6 copper wire to feed the garage to handle the heat load. The house panel will need a 60-Amp breaker also.