Can I connect a household heater to a 240V garage outlet?
A 220/240v single phase outlet (they are the same)  is not what you would want to plug a 120v 1500w heater into. If that heater is tripping a 15 amp breaker there is something wrong as it should only be drawing 12.5 amps. 
Most mobile power outlets are 120v 30amp or 240v 50 amp. In either case it would be a code violation to plug this heater in because both breakers are two large (even an adapter cord is used on the 240v)