Anything I should know about putting GFCIs at a work bench?

[cdev]

Basically, I have two GFCIs and I am wondering if there is anything I should know about their use in an electronics workbench setting? I am not anticipating any dangerous conditions, actually almost everything I fool around with is low voltage -  I'm just planning to replace the current wall outlets with GFCIs, does that sound like a good plan?

[SL4P]

Basically, I have two GFCIs and I am wondering if there is anything I should know about their use in an electronics workbench setting? I am not anticipating any dangerous conditions, actually almost everything I fool around with is low voltage -  I'm just planning to replace the current wall outlets with GFCIs, does that sound like a good plan?

The thing you need to know is that you're smarter than most semi-pro elec techs and engineers.
Make sure you test the devices before you need to depend on them, and keep in mind that you may want a 'dirty' circuit as well for permanent appliances - like phones & heaters etc that are not in the immediate workspace.
Also remember that mains leads that you run over with your chair, or drop the hot iron on - are worthy candidates!

[kizzap]

In case you haven't figured it out yet, a GFCI will only trip on faults (either Line or Neutral) to EARTH. It will happily supply up to the Circuit Breaker's rated current (which can be upwards of 100A depending on the breaker/time). Basically the GFCI will do shit all if you short Line and Neutral together.

I don't know much about the American (and I am assuming you are, happy to be proven wrong), but in Australia you can get RCD(GFCI)/CB combos, which will detect either fault and trip. Might be worth looking into that?

[SeanB]

In the USA ( that you get GFCI outlets anywhere in the world other than the USA I have never seen) so yes, putting them in is a good thing. I would also recommend that the regular outlets are also replaced with AFCI outlets, as they protect against arcing faults as well. GFCI on stuff to the bench, and AFCI on the rest of the room.

[Zero999]

GFCI is called RCD in most other parts of the world.

I've never heard of AFCI.

[Ian.M]

The rest of the world calls them RCDs and they are certainly available as sockets in the UK.   However we rarely bother as 30mA trip current RCD protection for all outlets is now more-or-less mandatory under our wiring regs. (there are a very few exceptions) and it is commonly done using a whole-house RCD on the incoming supply.  This is IMHO dangerous as you loose all the lighting if it trips.

More sensitive individual socket RCDs are prone to nuisance tripping, commonly caused by high level common mode noise, so I'd want at least one outlet that didn't have RCD protection (other than any whole house protection that may exist)

If you are building a serious multi-station workbench, it may be worth getting a high current circuit run to a high current industrial socket behind the bench then having an appropriately rated flexible lead and plug to a consumer unit (sub-panel / breaker box) with individual arc fault RCB0 breakers for each outlet or station on the bench.   That gives you a single point to shut off the whole bench - useful for peace of mind at night, and also the dedicated supply means you have fewer worries about power quality or ground loops. Considering the bench as plug-in equipment, in most jurisdictions you can wire it yourself without a formal electrical inspection, which may not be the case if you replace wall outlets other thanlike-for-like.

[LabSpokane]

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.

[free_electron]

arc fault interrupter in the fuse box. gfci in the outlets.

standard breakers work on a thermal principle. create a short : heat up the internal element and they pop
AFCI are magnetic. create a hard short and the current spike sets of a magnetic system the pops the breaker. so these things react to huge inrush currents. if you have an intermittent arc a thermal breaker may 'average out' the current and not trip. an AFCI will trip because the arc current is much higher.

the american power system is retarded.

in europe you can get GFCI + AFCE + breaker in 1 combo element. my parents home is 50 years old and already has such devices installed. AFCI are just now becoming avaialble in the Us but not mandated by code.

same stupidity as running double insulated wire inside drywall ... one rodent and the house goes up in flames. power cables need to run in conduit.

[ajb]

AFCI breakers are actually mandated in all living spaces (so, basically over the entire home) in many parts of the US now.  GFCIs are still only required in potentially wet locations, typically.  I'd be curious how well the statistics bear out the emphasis on arc fault versus ground fault protection, in terms of actual lives lost to preventable instances of each fault.  Given the lower voltages and commensurate higher currents in the US system versus most European systems the difference in emphasis would seem to make sense, but I don't see any reason why both shouldn't be more widely used.

[AG6QR]

Generally, it's better to have a GFCI than to not have one.  However, they don't protect against everything, so the presence of one is no excuse to get sloppy about safety.

In particular, as Kizzap says, they only protect against faults to earth.

As a consequence, if you're using mains to feed an isolating transformer, a GFCI offers no protection whatsoever to anything on the secondary side of the transformer.  The GFCI merely insures that the line current going to the primary of the transformer is all returned via the neutral, but the GFCI doesn't "see" anything that's happening to isolated secondary.

This sort of situation sometimes comes up on a test bench when someone uses a 1:1 isolation transformer in order to "float" a device under test so that a non-isolated oscilloscope may be used to probe it.  If you clip the scope's ground lead onto something that is close to line potential on the DUT, then other parts of the DUT normally at neutral potential may carry full mains voltage with respect to ground.  Touching such parts of the DUT while touching something grounded could give you a solid shock of mains voltage, and the GFCI won't prevent it.

Of course, without a GFCI, you'd still have the same potentially dangerous situation when using an isolation transformer.  The GFCI didn't make anything worse, unless it made you feel invincible and protected, causing you to drop your guard.

[Zero999]

arc fault interrupter in the fuse box. gfci in the outlets.

standard breakers work on a thermal principle. create a short : heat up the internal element and they pop
AFCI are magnetic. create a hard short and the current spike sets of a magnetic system the pops the breaker. so these things react to huge inrush currents. if you have an intermittent arc a thermal breaker may 'average out' the current and not trip. an AFCI will trip because the arc current is much higher.

the american power system is retarded.

in europe you can get GFCI + AFCE + breaker in 1 combo element. my parents home is 50 years old and already has such devices installed. AFCI are just now becoming avaialble in the Us but not mandated by code.

same stupidity as running double insulated wire inside drywall ... one rodent and the house goes up in flames. power cables need to run in conduit.

Here in the UK the standard circuit breakers fitted in homes are magnetic.

Is it normally one GFCI per socket in your part of the world? 5mA sounds like a very low trip current, if it's for more than two appliances.

RCDs are 30mA here and protect many appliances running from the same circuit. I suppose the higher current isn't so safe but there's less nuisance tripping.

[LabSpokane]

It's normally one GFCI device per string of outlets that need protection. Our outlets are designed to be daisy-chained. In fact, putting more than one GFCI device on a circuit usually doesn't work. Typicallly only the first GFCI In the series will trip regardless of the fault location.

[NiHaoMike]

Some GFCIs and AFCIs have a tendency to false trip under high noise conditions. Buy from a store with a good return policy.

Also, a GFCI will be useless with an isolation transformer.

[Kevman]

standard breakers work on a thermal principle. create a short : heat up the internal element and they pop
AFCI are magnetic. create a hard short and the current spike sets of a magnetic system the pops the breaker. so these things react to huge inrush currents. if you have an intermittent arc a thermal breaker may 'average out' the current and not trip. an AFCI will trip because the arc current is much higher.

I'm almost positive that a standard circuit breaker in the US is both magnetic and thermal, regardless of AFCI or not.

[SeanB]

Older ones are mostly thermal, with only newer ones ( from the 1980's here in South Africa) having in addition to the thermal bimetal a magnetic trip coil. Remember that they only have to trip faster than the wire can overheat. It is only recently that breakers also had to include extra functionality to handle things like small overloads which can overload marginal wiring, and things like user safety and protection against arcing faults in sockets.

[jlmoon]

Not sure why anyone would want GFCI breakers on their workbench unless they're working in their bare feet or standing in a pool of water or if you have a metal grounded bench it might be a great idea.  But for the most part sounds like more trouble than they are worth.
Any slight leakage of suspect equipment you might be working on is going to trip them, adding another unknown to the path of troubleshooting.  I prefer to treat all my bench areas as plug in appliances to dedicated and isolated grounds as to reduce the common mode noise and any ground loops that are easy to create.
 

[cdev]

Actually, I could probably be a poster child for how everything is increasingly low voltage and DC centric.

I just think its a kind of matter of principle to have even more- an extra level of protection.

[gwideman]

Not sure why anyone would want GFCI breakers on their workbench unless they're working in their bare feet or standing in a pool of water

I realize this is rather an old thread, but to answer this point:
You are right to observe that the GFCI will only trip on current that "escapes" from the Line-Neutral path.  That can easily happen if you inadvertently create a path from any live part of the device under test to a grounded terminal or case of some test equipment, for example a scope.

As to a grounded workbench surface -- this sounds like a terrible idea. The user would almost always have some body part in contact with that surface, so any single arm touching a live part of a circuit will always give a shock. Ie: The "One hand rule" would become useless.

[Psi]

This is not GFCI/RCD related but make sure your work-bench/work-room has a master power switch. 

So you can flip one switch off and walk away with everything powered down.
Accidently leaving something on is quite a high fire/safety risk with electronics.   Hot air/ soldering irons/ pre-heaters / solder pots / reflow ovens / high current circuits ...  All things that get HOT and are able to catch on fire and burn your house down.   

If you are in the room you can easily stop problems from becoming fires, but if your asleep in another room or out of the house you can't.

Just last month my hot air gun slipped out of its holder and was point blank pointing at my wooden desk.
It had already made a rather large burn hole in the desk and was well on its way to starting a fire before i noticed the problem and stopped it, and i was in the room.

[JustMeHere]

So I had a house that had no earth but a GFCI panel to get it up to code.  (Well the bathrooms still had to be grounded, so I had to pay for that.) 

These things trip when less power comes back in N than goes out on Load. 

N is connected to Earth in the panel.  So it's I'm not sure it can "fault" to Earth.  It can become disconnected.   

I did ultimately run a grounded line to my office.  That circuit would trip every time lightning would strike too close.

[paulca]

My office and workbench are on several RCDs.

The whole house is on a 100mA trip at the 'tails'.  The workbench circuit is power off an inverter with mains transfer switch and RCD.

Install them, forget they are there.  Maybe, maybe they might save you, but never rely on them.

EDIT:  I tested my main RCD in anger accidentally one day.  I pulled the fuse for the lights with the intent on cutting the light feed wire for the garage out of the 240V circuit and converting it to 12VDC.

Fuse out I cut through the 1.5mm T&E and Boom, power off.  Why?

The cutters shorted N to E, enough potential exists in the voltage drops to cause current to flow.  Trip.

[EPAIII]

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.

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.

[watchmaker]

In my "lab" area (corner of the basement) the bench is powered by (2) 12 output switched 120 v strips.  These are in turn plugged directly into a GCGI/AFI which is wired to the panel protected by a whole-house surge protector.  After burning up two microwaves in Maryland lightning storms, I learned the value of the latter.  Also, I found one of my switched machine tools smoking.  Had no problems for ten years after that.

I do use an ESD mat/strap on a wooden bench (doors on saw horses, I am a "farmer" at heart); in defense, my setup is temporary as I figure out what I need (MORE space!).  But I avoid (emphasis on avoid) probing over 120 vac.

This set did save me when I was troubleshooting a BK501a and I knocked the collector of a high voltage transistor to the grounded frame.  The GFCI/AFI reacted in time to save the device and scope and the one-hand rule protected me.

The central switching at the bench is highly convenient, inexpensive, reduces electricity usage, and adds another layer of equipment protection.

As to whether the ESD protection is overkill and risky, I accept current industry practice.  This is all as an extremely raw amateur.

[soldar]

arc fault interrupter in the fuse box. gfci in the outlets.

standard breakers work on a thermal principle. create a short : heat up the internal element and they pop
AFCI are magnetic. create a hard short and the current spike sets of a magnetic system the pops the breaker. so these things react to huge inrush currents. if you have an intermittent arc a thermal breaker may 'average out' the current and not trip. an AFCI will trip because the arc current is much higher.

the american power system is retarded.

in europe you can get GFCI + AFCE + breaker in 1 combo element. my parents home is 50 years old and already has such devices installed. AFCI are just now becoming avaialble in the Us but not mandated by code.

same stupidity as running double insulated wire inside drywall ... one rodent and the house goes up in flames. power cables need to run in conduit.

I believe you are confusing things.

European and American circuit breakers both can be tripped by a bimetallic element heating up and by a solenoid. The heat element is slower acting and the magnetic element is faster acting. Between the two elements they provide a certain trip time as a function of the overcurrent.

GFCI are generally provided in America at the outlet level whereas in Europe they are generally in the general panel. Each option has its pros and its cons.

And AFCI are ARC Fault Circuit breakers, totally unrelated to the previous ones.

Edit: https://www.realpars.com/blog/circuit-breaker

[AVGresponding]

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.