General > General Technical Chat
Anything I should know about putting GFCIs at a work bench?
JustMeHere:
--- Quote from: EPAIII on May 01, 2024, 09:59:28 am ---Why on earth would you deliberately provide 1/2 of a circuit that could kill you?
In addition to years as an electronic hobbyist, I worked over 45 years with all types of electric and electronic equipment, including high powered (high Voltage) commercial transmitters. In all of that time the worst shock I ever got was when about 40,000 Volts passed through my body, through my shoes, and into the grounded, METAL workbench I was working at. I know that was the path it took because I found the burn holes in my hand and on the bottom of my foot.
IMHO, the last thing you want is a grounded workbench. And I think I know what I am talking about. I don't even like those grounded mats for the top of the bench that are supposed to prevent static damage. When I find one I either disconnect it or toss it away. In that same time period I have never seen anything damaged by static discharge. Those mats serve NO PURPOSE.
Oh, and when you see a Voltage specification on a probe, BELIEVE IT. That 40,000 V also went through or around a meter probe I was using. The meter, a Simpson 260, was OK.
--- Quote from: LabSpokane on April 07, 2015, 06:28:50 pm ---The US standard GFCI is designed to trip about 5mA, not 30mA. They are an excellent idea. Consider grounding your workbench, etc if it is metal. I specifically chose metal pegboard mounted to Unistrut so that I would have a solid ground in case devices mounted there faulted.
--- End quote ---
--- End quote ---
I heard a story just like this yesterday....bench was grounded. Worker was tired. Had one hand on the bench and accidentally brushed a welding rod across his forehead trying to wipe sweat away. Zap.
If only his project had been grounded, he would still be here.
jonpaul:
55 yrs experience in power electronics to 75 kV and 12 kW.
Never needed GFI or AFCI breakers.
Nor grounded metal bench
120V mains >>10A Variac >>1:1 isolation trsf (Signal 2 KW 120/240 dual DU-2) >>bench, DUT
Scope is earthed to ground and DUT/SMPS floats.
The Arc Flash breakers are junk and usually false trip on EMI.
GFI needed ONLY in wet environ, eg bathroom, toilet, kitchen.
IF your workspace is in a bassement eg. damp concrete floor,
1. Get thick rubber matt
2. Wear rubber sole shoes
3. Yes ONE GFI per line of outlets may be useful.
Be safe,
Jon
Kasper:
--- Quote from: jonpaul on May 02, 2024, 04:40:11 am ---
The Arc Flash breakers are junk and usually false trip on EMI.
--- End quote ---
Mine sometimes trip when I turn on table saw or mitre saw. It is very annoying.
paulca:
--- Quote from: AVGresponding on May 01, 2024, 04:39:26 pm ---The most important thing to remember when you have GFCI/RCD/RCBO protection is that THIS DOES NOT MAKE YOU SAFE. It only reduces your risk.
--- End quote ---
Like an airbag in a car.
nctnico:
--- Quote from: EPAIII on May 01, 2024, 09:59:28 am ---I don't even like those grounded mats for the top of the bench that are supposed to prevent static damage. When I find one I either disconnect it or toss it away. In that same time period I have never seen anything damaged by static discharge. Those mats serve NO PURPOSE.
--- End quote ---
You couldn't be more wrong about anti-static mats. ESD damage is real and I have first hand experience with that. Several decades ago I build & sold PCs (using the same brand & type of components) and I used an ESD safe workbench for that. But at some point I didn't have enough space so I assembled a PC at a regular desk and carpet on the floor. Long story short: within a year I had to replace every part of that PC. One thing after another broke. I never had that problem with any of the PCs I built at the ESD safe workbench. That was an expensive lesson.
And I do make it a point to run my workbench mains from a GFCI / RCD. All test equipment is grounded so basically you can grab ground at any point on a typical electronics workbench. Equipment gets older and could develop a ground leak or so. So when something mains related fails then at least the GFCI will trip instead of letting the situation get worse and pose a shock hazard to me.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version