[PSUBS-MAILIST] Re: SAFETY, Carsten's electrical failure

[David Buchner <buchner@wcta.net>]

Carsten, 

You recently wrote something about relays failing in your earlier boat, where you had neglected to protect the circuit with a fuse [I find that I've deleted the messages from that day, and can't locate it after a quick look, so I don't have the specifics here to quote].

I'm always interested in real-life stories of malfunctions and fires and troubleshooting, whether in subs or cars or houses. They lend an understanding that goes beyond just "following the code because it's the code." I want to know just what I'm protecting against.

For example, I'm always disappointed when a newspaper tells of a house fire that "apparently started in the kitchen wiring," and they DON'T tell you that it was an old brittle 18-gauge extension cord running the refrigerator from a concealed receptacle with a broken faceplate, crammed full of dust and cooking grease and mouse droppings. And that it had been making arcing sounds for the last few years whenever the frig motor started, and they never got around to checking it out...

So I'm interested in knowing a little more about this relay problem. First, your using two in parallel to handle twice the amps made sense to me too -- so why didn't it work? Second, I'm having a hard time at the moment seeing how a relay could burn out in a way that does something besides give you no thrust (coil doesn't work anymore) -- or leave you unable to STOP thrusting (contacts welded together). Apparently, it caused a short circuit. Do you know how? Did a chunk of metal inside the case come loose and fall across two contacts?

Thanks for any light you care to shed on this.