Circuit Breaker blogging

What a wonderful day today was... [set sarcasm=off] We had a power outage last evening that came back around 2:00am this morning. I didn't bother to go down to the store as the power had been off for only about three hours -- the freezers are well enough insulated that they can be without power for a good ten/twelve hours. Well, around 11:00am today, we noticed that the internal temperature was 25 degrees and rising and that a lot of the food was starting to thaw. Well crap! Total loss was around $800 at our cost for the food plus an unknown amount for the emergency call to our refrigeration people. What had happened was that when the power came back on, the starting surge of the compressor tripped the circuit breaker. This is a 40 amp breaker and the nominal running current of the compressor is around eight to ten amperes but the breaker was failing. Circuit breakers are designed to fail conservatively -- if you have a 40 amp breaker and it starts to fail, it will trip at lower and lower currents. This is by design as if the breaker failed the other way, you could have an equipment malfunction and the breaker would not trip causing potential overcurrent and fire hazards. Talk about hoist by one's own petard... Anyway, the food is still fine, it never got to unsafe temperatures, it just cannot be refrozen. It is sitting in our walk-in cooler and the Bellingham Food Bank will be getting a lot of nice Pizzas, Juice concentrate, Fruit, Veggies and Box Meals tomorrow morning.