1) If you have chronic problems with electronic timers, then circuit is suspect. Buy cheap circuit analyzer and plug into same outlet. Try timer on different outlet on different circuit breaker. Change Load (lamp, fan) to see if same problem occurs with different load.
2) Maximum load for GE 15091 is 600 watts incandescent. There is no HP rating, so timer probably not made for motor loads since motors draw high initial amperage. For heavier duty timer, with 1250W incandescent and 1/3 HP, select Woods 59201.http://www.amazon.com/Woods-59201-Appliance-Grounded-3-Prong/dp/B001Q9EFTQ
3) I have tested GE timers. They are made well.
The 15091 is sold under different brand names, so it is successful design that's been around a while.
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Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.