so I had a fire sunday morning...

[MrMobodies]

I remember Bigclive did a teardown video of one with movs that did explode:




I think when they wear out (some have leds to show that the mov is working) either bin or dissect them of their movs but I see they are in a lot of other stuff as well.

[jmelson]

I'm glad you're OK.

It obviously wouldn't help in a situation like yours, but this does make me think about what type of fire extinguisher I should be keeping in my electronics lab (I currently don't have any).

Anyone got any advice?

This is not the best for electronic gear, or anything that still has power on it, but I got a bunch of retired air over water extinguishers years ago on eBay.  They have a couple gallon tank that you then pressurize with an air compressor.  It has a gauge that shows the air charge is still there.  The only time I used it, some turkey fat caught fire in our oven.  I sprayed the water against the back of the oven, to create a shower of water droplets, not right on the fire.  It put it out within one second!
I used about 2% of the contents of the extinguisher.

Anyway, these things have to be retired from commercial use after 5 years, but they are built like a tank.  (Huh, well, actually, they ARE a tank, of a sort.)

Jon

[Brumby]

The only time I used it, some turkey fat caught fire in our oven.  I sprayed the water against the back of the oven, to create a shower of water droplets, not right on the fire.

Your approach showed some understanding of the dangers of a fat fire.  Spraying such a stream directly on the fire is the normal reaction - and this would have had created a bigger problem.


* A general comment to anyone considering acquiring a fire extinguisher - do your homework, get the right one, think carefully about where you put it and know how to use it.

[coppercone2]

 ithink your actually steam-clogging the fire by breaking the fire tetrad with oxygen with what you were doing, in addition to evaporative cooling.

It's a solid strategy for equipment/turkey protection, its how fire fighting ends up working in ships (you clog the compartment with steam to prevent combustion moreso then cooling it, you slowly cool it from the outside (sometimes if its possible) so its safer).

obviously no good for protecting people, and keep in mind hot enough steam will ignite stuff too. You don't want too much steam if you are trying to rescue people or they will get cooked or suffocated.

https://www.newscientist.com/article/dn4738-fighting-fire-with-a-steam-machine/

https://www.quora.com/Has-steam-been-used-to-fight-fire-It-displaces-air-and-is-not-lost-to-the-ground

[IanMacdonald]

I've three smoke detectors in the building, but of course that won't help if there is no-one in. This has got me thinking that a spare optical smoke detector (the type that doesn't give so many false alarms!) interfaced to a contactor might be an idea. One approach would be to have it trip the bench RCD by injecting a small ground current. So if power's been left on, the appearance of smoke kills the power. Could add a small delay so that the trip can be cancelled if the smoke is not a danger sign.

Maybe a kickstarter idea that could sell to a lot of hobbyists, not only in electronics?

I have some MOV-containing extensions, think a job for this evening will be to rip them out. They are useless gimmicks anyway.

[Red Squirrel]

I do eventually want to look at building a modular home automation system that would essentially work around the idea of contactors and dry alarm points.  Could then make it do all sorts of stuff such as take specific actions if smoke detector goes off. Maybe even turn off water main if a leak is detected. Stuff like that.   

[coppercone2]

I don't think their useless gimicks, I think they should be standardized with some kind of integrity monitor and sold like fuses in some kind of module that can be replaced in various consumer electronics. Or just make the entire filter/fuse/MOV assembly that is standardized for consumer equipment and protect everything. 

They do clamp spikes after all...

What you can do is trick them out with more MOV's (their cheap) in parallel so long you don't hit the leakage, or put a GDT in series with the MOV.