Mine ran last Saturday afternoon for 1.25hrs from a Local P/O I came home an she was running about 20 minutes later she re'transferred, cooled down, then shut off. Went out an recorded the ending run time change, in the log. Around here it's normal for her to run 2-4 times a month for up to 3-4 hrs at a time do to weather or people who can not drive. It's a 25kw so it will pull the whole house an shop at once.
Once you know how a device, system, ect operates, finding the root cause in the event chain is easy. Until then, you will always be chasing/repairing the effects. Learning is a life time event, if you want to outsmart, whatever item you want to repair.