That moment when you blow a circuit breaker... - Page 1
Forum section: electronics / general

author: Phaedrus
author_rank: Frequent Contributor
timestamp: June 16, 2014, 10:27:40 pm
content: Anyone else have it happen to them often, when they're working on a project or testing something, when suddenly there's a *SNAP*, the lights go out, and all your equipment turns off? Then the sinking feeling as you wonder if you're gonna have to call the insurance company?Yea...Just had a 1kW PSU fail with a dead short across the AC input. Good thing I have spare fuses for my power meter... And thank christ nothing important was damaged.

author: David_AVD
author_rank: Super Contributor
timestamp: June 16, 2014, 10:31:34 pm
content: That's why you should have a separate breaker for the work bench power.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: June 16, 2014, 10:41:19 pm
content: We've got a 40A circuit specifically for our electronics lab. I think the lights are actually on a different circuit, they didn't go out this time (though they did go out once in the past for some reason). If I could isolate different equipment on different sub-circuits that would be awesome: power meter(s) and PSU under test on one circuit; DC loads, PSUs, scopes, etc. on another circuit; and the lab PC on a third circuit. Unfortunately management won't spring for an electrician right now.

author: djacobow
author_rank: Super Contributor
timestamp: June 16, 2014, 11:02:09 pm
content: I wired my own shed/workshop and one of the things I most regret, is not putting separate equipment / DUT circuits above the bench. I only have one 20A circuit feeding the bench area. Dumb, dumb, dumb. There is a separate lighting circuit, though, so I can still see my way to the breaker panel.

author: tom66
author_rank: Super Contributor
timestamp: June 16, 2014, 11:20:38 pm
content: Why would a breaker popping damage things?I've popped far too many, no damage yet -- at least nothing directly attributable.Things like hard discs in computers, maybe heating elements cooling too rapidly (my hot air station being a potential example), or stuff like that?

author: Tinkerer
author_rank: Frequent Contributor
timestamp: June 16, 2014, 11:21:40 pm
content: The most recent one was at work. A certain engineer(no, not me) wasnt watching what he was doing and blew a small crater into a connector shell.

author: David_AVD
author_rank: Super Contributor
timestamp: June 16, 2014, 11:34:30 pm
content: If you do use separate breakers, make them MCB/RCD combo types instead of the upstream breaker having the RCD. Otherwise a ground fault will still see everything go out.(RCD = GFI in USA I think)

author: Phaedrus
author_rank: Frequent Contributor
timestamp: June 17, 2014, 01:41:09 am
content: Quote from: tom66 on June 16, 2014, 11:20:38 pmRapidly switching off 30A @120VAC is going to give you one hell of an inductive transient before voltage drops to zero.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 17, 2014, 02:46:59 am
content: Quote from: Phaedrus on June 16, 2014, 10:27:40 pmReal circuit breakers don't go "SNAP!",they go "KA-BLAMM!!" & shake the whole building!

author: johansen
author_rank: Super Contributor
timestamp: June 17, 2014, 02:54:50 am
content: i just melted the glazing off a patch of ceramic tile on top of my aluminum work bench when an errant ground wire twisted around and hit the 120vac line on a terminal strip.funnything is, the ancient 20 amp breakers in my shop, never tend to blow unless i overload them for a long time, like 30 amps for 20 minutes.its always the 60amp breaker that feeds the entire shop that blows instantly. must be magnetic or something.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 17, 2014, 05:47:32 am
content: Quote from: johansen on June 17, 2014, 02:54:50 amSeems a little long for a 1.5x overload, but not really outlandish...Think of a fuse as guaranteed OK at rated current, guaranteed to blow in a reasonable time frame (seconds) for at least triple that current!Tim

author: KSP
author_rank: Regular Contributor
timestamp: June 17, 2014, 09:51:26 am
content: We have an RCD on every single bench. Computers get plugged into the wall, and equipment to the benches. This really limits what goes out in the event of a fault.I advise this setup

author: Skimask
author_rank: Super Contributor
timestamp: June 17, 2014, 10:59:34 am
content: So, the electrician said I blew a circuit breaker.I said " just fix the damn wiring and leave my personal life out of this..."

author: TerraHertz
author_rank: Super Contributor
timestamp: June 17, 2014, 11:24:17 am
content: Quote from: djacobow on June 16, 2014, 11:02:09 pmQuote from: David_AVDOhhh.... poop. Over the last couple of weeks I've been doing a long-overdue upgrade of the wiring in my workshop. Fairly major rework. Just about finished everything now.And yet the idea of having an entirely separate DUT outlet on the main workbench, with its own RCD & breaker totally didn't occur to me. Apparently I'm getting stupid in my old age.It's a very good idea, thanks.Hmmpf. To rub it in I even happen to have a spare single phase RCD, and there are exactly three spare slots in the main panel to fit the RCD and breaker. Sigh. More threading cables through walls. Great.

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2014, 05:45:09 pm
content: You think you got problems, I have been doing some renovation at work, and have had to coordinate turning off entire systems as needed to disconnect for temp working. Computers were easy, announced over PA that there would be a shutdown in 5 minutes, and to log out NOW. I am sure some were still playing sol when the power went out...... Did my thing and turned power back on 5 minutes before closing time. Will see tomorrow how many complain the computer does not work ( no idea what that button on the front does) and that I broke their computer. I made sure the server stayedc up in the interim, as that cable was not part of the affected area. Tomorrow alarm cabling to move and repair where the bash and crash builders have been. Got a big box of redundant lights and fittings as well, and a taker for them.

author: djacobow
author_rank: Super Contributor
timestamp: June 17, 2014, 08:23:58 pm
content: Quote from: TerraHertz on June 17, 2014, 11:24:17 amYeah, it's a bummer realizing you just a missed opportunity, My walls are now closed and I can't get myself to tear up sheetrock just for this purpose. It sounds like you can still get cables in your walls. That's good news, right?

author: G7PSK
author_rank: Super Contributor
timestamp: June 17, 2014, 08:38:59 pm
content: Self adhesive trunking, and run it over the surface, do right and it hardly notices, I have just used it to run cat cable in the house following the skirting boards and door jams. Saves one hell of a lot of chasing.

author: David_AVD
author_rank: Super Contributor
timestamp: June 17, 2014, 09:10:09 pm
content: If anyone comes up against the problem of not enough DIN slots left in their switchboard to add RCDs, don't forget hat you can get RCBO (combo units) in single pole width size now. I got my house redone with these so every power circuit has its own RCD. That way there was room to add the new dedicated circuits for my games room and Christmas lights.

author: nctnico
author_rank: Super Contributor
timestamp: June 18, 2014, 01:06:14 am
content: I'm using an extension cord from the washing machine outlet for testing high power stuff. I had some 'mishaps' in the past and it sucks to have to find my way down 2 staircases in the dark to switch the electricity back on.

author: TerraHertz
author_rank: Super Contributor
timestamp: June 18, 2014, 01:56:41 am
content: Quote from: SeanB on June 17, 2014, 05:45:09 pmWith the main workshop wiring undergoing alterations, it had to remain all disconnected at the main switch (in another building) most of the time. Fortunately, my machine tools shed (an old fibro garage) has separate power and a walk through connection to the main workshop. So this is what the floor in that passage has looked like for the last couple of weeks. Behold, extension cords.