New lab - no grounded outlets

[staxquad]

live, neutral and grounded cable (~$30/10M?) from it's own breaker (or glass fuse?) in the fuse (breaker) box  (if there are spare) to that lab room, add as many sockets as required, voila (Bob's your uncle), or revamp your electrical   

done already, and while you're at it, add a few outlets in the house here and there as required (and some indoor and outdoor GFCI)

power trip

don't fart around, do it once correctly

Our ground (Ontario Hydro dictated) is the 1/2" copper water pipe from the city supply (now 3/4") and comes through the basement wall at floor level (8 ft deep outside).   A clamp secures a thick bare copper ground wire on that pipe that goes back to the breaker panel.  Only 2x hot and a neutral wire from Ontario Hydro connect to the breaker panel after passing through the meter.   

[edavid]

Has anyone tried using a neutral ground resistor (or some other clamp circuit) to absorb the Y capacitor leakage?  Does this violate code?

[alm]

Yes, I'm pretty sure this is a code violation in most countries. The neutral should have the same insulation and creepage as the live wire, because wires can get switched or neutral wires can become open.

Hint: what's the voltage on a neutral wire if the neutral connection to the power distribution transformer gets cut somewhere? This is a resistive divider with an extremely high resistance between equipment ground and earth, and a relatively low resistance of all the parallel equipment connected between live and neutral.

Grounded three pin and ungrounded two pin electrical outlet systems are each individually safe as long as they are used consistently and not mixed in the same room or workplace. The two pin system is (was) considered safe as long as the outlets are in a dry room with no exposed metal pipes or other earthing points within reach of the sockets. As soon as you introduce one earthed or grounded item into the environment the whole setup becomes unsafe.

I guess that they didn't ground water pipes or radiators back then either?

You might be able to derive a ground from something like a metal water pipe or cable TV connector. Use a 100W or so bulb to check the ground impedance and if that's good, add a GFCI/RCD. (If you don't like the idea of doing DIY mains wiring, an off the shelf solution is a plug in GFCI and a surge protector with coaxial connectors.)

This is a code violation in most places. What happens if a metal pipe gets replaced by plastic during maintenance? What if some poor plumber disconnects a pipe and then gets shocked from the leakage current of all Y caps in the equipment you have connected? Keep in mind that he/she is most likely working in a wet environment. I wouldn't trust a TV cable either, the ground connection should be able to carry enough current and have a low enough impedance to trip a breaker in case of a short, or at least until the GFCI trips. I expect the coaxial shield to burn up very quickly if you connect it to 115 V / 230 V (which is what happens in case of a fault it's supposed to protect from).

[Stonent]

Some of the long outlet strips you can buy have an external grounding screw, you could try to run that to a safe location.

[IanB]

I guess that they didn't ground water pipes or radiators back then either?

I imagine they did, but you would not be allowed to have exposed metal pipe in a room with two pin outlets. It must be impossible to come into contact with any kind of earth in a space where two pin outlets are used.

[madires]

I guess that they didn't ground water pipes or radiators back then either?

I imagine they did, but you would not be allowed to have exposed metal pipe in a room with two pin outlets. It must be impossible to come into contact with any kind of earth in a space where two pin outlets are used.

Then the people living in that house need to float 5cm above the floor :-) The building itself is earthed! It's not a good conductor but most times a few mA can flow. If the wall socket has no ground the few mA won't maybe trigger the RCD but could be enough to hurt you. A grounded wall socket makes sure that there's a good ground connection for a broken device, i.e a hot metal case would trip the breaker or trigger the RCD quite fast. As I wrote before we have also to consider the outside world. One tap of the pole/substation transformer is earthed/grounded (this is the neutral wire).

[IanB]

Then the people living in that house need to float 5cm above the floor :-) The building itself is earthed! It's not a good conductor but most times a few mA can flow.

It's not that bad. In a dry indoor room with wooden floor there is no path for a dangerous leakage current to follow. In my misguided youth I worked quite obliviously with a live 240 V bare wire while kneeling on the concrete floor of an outdoor garage and felt nothing at all (I forgot to unplug the circuit before working on it). I only remembered it was live after I accidentally touched the wire to earth and tripped the breaker.

The resistance of dry building materials is megohms and no current large enough to feel will flow through that. (For instance with 1 megohm you would have about 240 µA.)

[Monkeh]

You might be able to derive a ground from something like a metal water pipe or cable TV connector. Use a 100W or so bulb to check the ground impedance and if that's good, add a GFCI/RCD. (If you don't like the idea of doing DIY mains wiring, an off the shelf solution is a plug in GFCI and a surge protector with coaxial connectors.)

Please nobody listen to this guy.

[duskglow]

It's not that bad. In a dry indoor room with wooden floor there is no path for a dangerous leakage current to follow. In my misguided youth I worked quite obliviously with a live 240 V bare wire while kneeling on the concrete floor of an outdoor garage and felt nothing at all (I forgot to unplug the circuit before working on it). I only remembered it was live after I accidentally touched the wire to earth and tripped the breaker.

When I was young, I accidentally touched a live 120V prong while standing on a linoleum floor while wearing shoes.  I felt it.  It was not pleasant.  I suffered nothing more than feeling like my finger was buzzing.

Obviously, though, this is playing with fire.  I am astonished that with the number of televisions I messed with with the power on I never got thrown across the room.

[IanB]

When I was young, I accidentally touched a live 120V prong while standing on a linoleum floor while wearing shoes.  I felt it.  It was not pleasant.  I suffered nothing more than feeling like my finger was buzzing.

I suspect you also were making contact with the neutral prong with another part of your finger. That would explain why only your finger was buzzing and not your whole arm.

An electric shock traveling up your arm makes your arm muscles contract involuntarily in a way that is highly unpleasant, like having all your muscles cramped at once.

[nukie]

Now I understand why I got zapped by the perfectly working 2 mains pin SMPS 12v. Bloody painful but not as shocking as 240v, stupid design!

[jmacqueen]

I have felt the result of screwed up ground wiring or lack of grounding on a customers brand new house while doing plumbing when I unfortunately discovered a 240v potential between the wet garage floor and the water inside/case/chassis of the 240v water heater by becoming a quite decent path to earth for it with just a touch, put my lights right on out in an instant and felt like a truck just hit me. Scared me to death when my vision came back, scared the customer even worse, and after I got off the phone with her building contractor there was an electrician on site before I left.

Personally I would drive a couple of 8 foot copper clad grounding rods outside the house and get a proper ground wired into the house or at least the lab from there. I just got finished wiring up my own home several months ago , a 1950's farm house I bought and had moved to the property I bought to retire to. First thing I did was drive a couple of ground rods outside by the incoming power and tied neutral and the breaker box chassis to good earth ground, and made sure I had a good earth ground run to all outlets in the house.

[staxquad]

I guess that they didn't ground water pipes or radiators back then either?

I imagine they did, but you would not be allowed to have exposed metal pipe in a room with two pin outlets. It must be impossible to come into contact with any kind of earth in a space where two pin outlets are used.

My house was build in 1939, only had 2 pin outlets with copper water pipe ground (coming from the town supply, 8 ft underground), exposed copper piping throughout the basement with outlets nearby.  Nobody knowingly would stick metal things into a socket, holding it with their bare hands while touching a grounded metal pipe with the other.  If they did they would win a Darwin award.  The wiring was under code.  The house is now 3 prong, with copper water pipe ground still, (upped amperage, new meter, panel, outlets, etc)

[duskglow]

The house I grew up in was built in 1894.  It was not only under code, it was dangerous.  When the furnace or washing machine would start, the lights would dim appreciably.  Sadly, we were renting so we couldn't get it fixed.

That was not the most dangerous thing.  The most dangerous thing was when the solenoid on the furnace gave out, and the landlord wouldn't fix it.  So my father (genius) stuck a jar and block of wood under it to hold it open.  To start the furnace, he'd open the valve and stick a flaming paper right in the gas stream.

When the landlord finally got around to fixing it, the repairman was astonished that the house hadn't blown up yet.  He ended up replacing the furnace.  That original furnace, I think, was 1940s vintage.  Or earlier.

I got the electrical parts from it when they scrapped it, so not all was lost.  That was a hefty transformer.  I probably would have killed myself if I'd had the nerve to power it up.

[Tepe]

In fact, almost every house in this country has 2-wire AC plugs

Assuming "this country" is the same one that I live in, I will add that of the eleven homes I have lived in, only the latest one has some outlets with PE and it only has them in the kitchen. As Paul wrote, this is very common for the 220V (now 230V) outlets. The 380V three phase outlets (now 400V) do have PE, but you don't tend to have those all over the house

Historically, PE seems to have been frowned upon in this country. In "Elektriske installationer", Eriksen & Hansen, 1960, the authors wrote that opinions varied strongly on the subject of PE in household installations  and while some countries like England and Norway held that all metal parts of an installation that was not live had to be grounded, others, including Denmark, have been more reluctant in making such a requirement.

If you go back in time in the literature, you will sometimes encounter rather strong opposition to grounding and discussions of whether the use of it makes installations safer or more dangerous.

Like it or not, this is the reality we live with here. And, yes, the typical mini tower pc in a metal box with an SMPS can tickle you if you touch it and a radiator at the same time. That is also something many of us have to live with.

[Paul Price]

Consider these points:

It might be so much easier and cheaper to install a single GFI interrupter in you fuse box of your building than to spend tens of thousands of bucks to rewire your house.

Tepe says it clearly, "Assuming "this country" is the same one that I live in, I will add that of the eleven homes I have lived in, only the latest one has some outlets with PE and it only has them in the kitchen. As Paul wrote, this is very common for the 220V (now 230V) outlets. The 380V three phase outlets (now 400V) do have PE, but you don't tend to have those all over the house "

You might have different opinions about this topic but reason must replace sophomoric and rude name calling as a way of establishing your opinions as the only correct authority.

You must consider that there are different ways to practice safety and in fact, these different ways do work well and are used by not just me but thousands of electronic service people in this big world. And the same non-grounding, GFI wiring standards are the standard for electrical connection  and the safety of household wiring in some countries, other than the one you are living in.

If you go about and ground everything in your work area with a good earth AC mains power ground...you might think you've eliminated any chance of shock hazard from improperly wired or properly wired equipment. But if you have one hand resting on the metal 3-wried grounded power strip on your work bench or holding anything else grounded with one hand and then accidentally touch a live AC mains somehow connected wire in a piece of equipment that you are working with, then you are exposing yourself to a possible lethal shock. If your grounded equipment or grounded metal power AC outlet strip was not grounded you would not be in such mortal danger, especially if I have a GFI interrupter in the AC power circuit in your building or house.

The best approach I have to this safety problem is to use an isolation transformer only on the  equipment D.U.T. and stay away from using dangerous earth grounds anywhere else on the workbench. This way neither I nor the equipment can be connected so as to get a shock from the AC mains.

Sometimes assumed safe practices may in fact create more danger in some situations.

 I say think about what I have said and remember  that you have a choice and a responsibility, as I have, to carefully decide why and under what conditions some safety methods are safe or not.

[Paul Price]

Maderes, You ask what kind of equipment...please see https://www.eevblog.com/forum/beginners/lc-power-supply-capacitor-value-question/msg251423/#msg251423

[westom]

When I was young, I accidentally touched a live 120V prong while standing on a linoleum floor while wearing shoes.  I felt it.  It was not pleasant.  I suffered nothing more than feeling like my finger was buzzing.

  Some building materials including linoleum, concrete, and some wall paints are electrically conductive.  Just another reason why two wire power circuits may need a GFCI/RCD.

  However the OP is talking about a lab.  Those unexpected electrically conductive material can create workbench confusion.  Just another reason why a (third wire) safety ground (and not just a GFCI or RCD) is important when doing lab work.  To avert confusion created by stray currents.

[madires]

If you go about and ground everything in your work area with a good earth AC mains power ground...you might think you've eliminated any chance of shock hazard from improperly wired or properly wired equipment. But if you have one hand resting on the metal 3-wried grounded power strip on your work bench or holding anything else grounded with one hand and then accidentally touch a live AC mains somehow connected wire in a piece of equipment that you are working with, then you are exposing yourself to a possible lethal shock. If your grounded equipment or grounded metal power AC outlet strip was not grounded you would not be in such mortal danger, especially if I have a GFI interrupter in the AC power circuit in your building or house.

Metal power strips with the metal gounded? Never saw any over here, i.e all power strips are plastic. I think it's designed that way to stay safe with very old buildings without a dedicated PE. BTW, in any case we should know what we're doing if dealing with HV. 

The best approach I have to this safety problem is to use an isolation transformer only on the  equipment D.U.T. and stay away from using dangerous earth grounds anywhere else on the workbench. This way neither I nor the equipment can be connected so as to get a shock from the AC mains.

The isolation transformer isn't fool proof either. Don't close the loop inside the DUT :-)

You must consider that there are different ways to practice safety and in fact, these different ways do work well and are used by not just me but thousands of electronic service people in this big world. And the same non-grounding, GFI wiring standards are the standard for electrical connection  and the safety of household wiring in some countries, other than the one you are living in.

The goal is to know how the local mains wiring works and to adapt your safety measures accordantly. But a proper grounding might be required for an ESD-safe working space, measurements of low values or connecting different T&M gear.

[jpb]

Metal power strips with the metal gounded? Never saw any over here, i.e all power strips are plastic. I think it's designed that way to stay safe with very old buildings without a dedicated PE. BTW, in any case we should know what we're doing if dealing with HV. 

Metal sockets with metal conduit are quite common in workshops and labs in the UK. In fact I have used them (via an RCD) on my workbench. I did so to cut down on the amount of mains electrical noise, but I think the idea generally is that they are tough against mechanical damage such as accidentally putting a power drill through one and because they are visible you know where the cable runs are.

[vk6zgo]

You must consider that there are different ways to practice safety and in fact, these different ways do work well and are used by not just me but thousands of electronic service people in this big world. And the same non-grounding, GFI wiring standards are the standard for electrical connection  and the safety of household wiring in some countries, other than the one you are living in.

Indeed,but you are falling into the same trap----many thousands of people throughout the world have used "PE" wiring & the associated equipment without any problems.
In fact,back in the day,many homes had domestic radios with "figure 8" power cables sitting in the kitchen in close proximity to earthed refrigerators,kitchen sinks,etc.

In Australia,these were all quite safe,as they used transformer type power supplies,so the Mains were pretty much restricted to the on/off switch & the transformer primary.

If they failed,they may well have been tested using bench test equipment such as VTVMs & Signal Generators,all of which were earthed.

The incidence of fatal electric shock to Radio servicemen was  vanishingly small.

Of course,these days,Test equipment is still earthed,but much domestic stuff is not.
What we DO have is RCDs as a mandatory fitment to any new wiring,so I reiterate,GFI/RCDs & PE wiring
are not mutually  exclusive.

Most of the panic about Electrical safety is overdone,at least as far as Engineers & Techs are concerned.

Over some 40 years in Radio & TV Broadcasting,I have known  about 4 people who died accidentally__
One crashed a "Pitts Special" stunt plane, two others died in falls,& one was washed off the rocks while fishing.

Electrocution?---not one!

[alm]

I would not want an ungrounded metal conduit with mains wires in unknown condition (how often do you open it to inspect the wires?) near my bench. A grounded metal conduit will trip the breaker or GFI/RCD if a wire ever makes contact. I don't like to rely on my carpet (which incidentally was not UL tested for mains isolation) to limit the current through my body.

How do countries like Denmark, which apparently consider using equipment with a three-prong plug in a two-prong socket, treat the difference between IEC protection classes? In many countries where grounded outlets are common, equipment either needs a ground connection (class I), or has to apply to more stringent double insulation standards to reduce the chance that any single fault will bring the user into contact with dangerous voltages. Double insulation is getting increasingly popular because preventing contact with mains wires is considered safer than blowing the fuse in case of contact.

Can you just design equipment to the lower class I creepage/clearance standards without providing a ground connection in countries like Denmark? Do manufacturers like Agilent or Rigol test their equipment for safety and EMC/EMI without ground connection before marketing it in Denmark? Are there building code requirements about a minimum impedance to ground, just like the maximum earth ground resistance required in other countries?

[david77]

What exactly are we talking about here? Does the OP's house really use electric sockets without PE connection like this one



Or is it just an older installation using sockets with PE contact but only two wires (L and PEN, TN-C) to connect them?

In the first case I'd say get an electrician in and have the house/flat rewired ASAP.
I'm not going to say that the second variant is state-of-the-art but there is usually no immediate danger - if the installation is in good condition and nobody practiced their DIY skills on it. There must be millions of homes across Europe still wired like that.

In both cases I fail to see what a GFCI could do to improve the situation as there is no separate (TN-S/TN-C-S) PE connection back to the breaker panel. Here in Germany a GFCI is not allowed in a TN-C installation as it would cut the PEN conductor, thus cutting the earth return path wich is strictly forbidden.

One could consider splitting the PEN (2nd case scenario, TN-C system) directly at the workbench and installing a GFCI there powering dedicated sockets just for use on the electronics workbench, while leaving the rest of the house/flat alone.

All this depends very much on local regulations, though. And it is certainly allways a good idea to have a GFCI at least for the bathroom and kitchen.

[vk6zgo]

The things we call RCDs in Australia are really core balance relays.
They compare the currents flowing in the Active & Neutral lines.
These currents should be equal in value.

If they are not,current is flowing back to the Neutral line some other way,(via something connected to Earth,& hence the Neutral at the entry point),so the device becomes unbalanced & trips.

It does not require any connection in the Earth circuit,so can be used with sockets lacking an Earth connection--although such sockets are not used in this country.

They would not work with a Mains supply which was totally floating from the power station to the power socket on your wall(inclusive)-----but I don't think such supplies exist,otherwise Paul's GFI would not provide him any protection either.

[somlioy]

OP already stated that his house has a RCD. Tho if the house has a bad local earth it might need to be improved. The requirement is a cutoff within 0.4s, max 30mA. RCDs are there to protect you from contact voltages below 50VAC.
Splitting PEN at the workbench is NOT allowed i Norway. TN-C is only allowed up to the first fuse box. After that, TN-S and nothing else. Anyway OP already stated that his house is fed by a IT-system (i.e no neutral/PEN).

If your house has a open wiring you could be unlucky. Electricians usually snipped the earth wire if they didnt use it.
Or maybe the wiring is hidden? THere might be enough room in the pipes for a PE-wire.