New lab - no grounded outlets

[Emil]

This turned into a very interesting topic

After reading all the replies, I think I need to provide some more additional information about the installation.

The house has a ground connection. Several rooms in the house have grounded sockets (bathrooms, kitchen, laundry room), however the living room and the bedrooms do not. I will use one of the bedrooms for my lab.

The electrical installation is in compliance with code as they were at the time it was built. (All grounded sockets would be required for new construction.)

The sockets in the rooms without ground does not have the PE connector. The sockets looks like david77's picture.
There is an GFI/RCD in the fuse box. It should trigger in <=100ms at 30mA.

It's an IT, not a TN installation. There are two conductors with 230V between the conductors and 115V between either conductor and ground. There is no neutral conductor.

Thor-Arne mentioned that ground wire may be installed and that they just used ungrounded sockets. I have been told this is not the case, but I have not opened any sockets to check. If I'm wrong about this, installing grounded sockets will be very easy.

[IanB]

I would not want an ungrounded metal conduit with mains wires

Surely an ungrounded metal conduit with mains wires would violate every electrical code on the planet?

I don't think you would ever come across that in a properly installed system.

[Tepe]

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.

That's where it starts to get fun. The current "Stærkstrømsbekendtgørelsen" incorporates the IEC classes and also states that class I appliances must be equipped with a special plug with a PE pin or have other means of establishing a connection to the installation's PE. Yes, the PE that you may or may not have in your house wiring. To make matters even more fun, the Safety Board actually writes that you may connect such a three pin plug to a two pin outlet with an extension cord having a three pin female connector at one end and a two pin plug at the other. Voila! But only if your outlet is of the non-PE variety, of course.

RCD (called HFI and HPFI here) is required in all homes but not in, for example, kindergartens. New installations are required to use a PE wire; except if the residence is from before April 1, 1975. You may replace a non-PE outlet with a new non-PE outlet. That doesn't count as a new installation.

You have no less than three choices for your new three pin outlet should you decide to get additional outlets installed, just to make sure the future will be even more fun:

The one to the right is the traditional type.

Can you just design equipment to the lower class I creepage/clearance standards without providing a ground connection in countries like Denmark?

I don't know.

Do manufacturers like Agilent or Rigol test their equipment for safety and EMC/EMI without ground connection before marketing it in Denmark?

Highly unlikely. They don't sell home appliances, so why should they?

Are there building code requirements about a minimum impedance to ground, just like the maximum earth ground resistance required in other countries?

I don't know about that either.

[madires]

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.

The RCDs over here do exactly the same, no PE is connected to them.

[alm]

[complex story about the Danish electrical system snipped].

Wow, sounds like they are trying to combine international standards with several different local conventions. I guess you can't very well go back and rewire thousands of old houses, but combining two very different safety strategies seems a bad idea to me.

Highly unlikely. They don't sell home appliances, so why should they?

Fair enough, but it would be useful for the people using them at home. They may include a statement like 'Only for use in labs by trained engineers', though.

[Tepe]

Wow, sounds like they are trying to combine international standards with several different local conventions. I guess you can't very well go back and rewire thousands of old houses, but combining two very different safety strategies seems a bad idea to me.

While something fishy does seem to be going on (what's the sense in going from having one type of outlet with PE to having the choice between three different ones?), I think most residential installations are TT with the mandatory RCD and adding PE to the outlets should be okay.

[megajocke]

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.

I can not answer for Denmark nor Norway, but it seems the situation there is similar to Sweden. In Swedish installations an area (usually a room) has either grounded outlets or ungrounded outlets, but according to code is not allowed to have both. New installations are required to use grounded outlets and RCD/GFCI.

Class II appliances use plugs that fit in both types of outlets and are allowed in both grounded and ungrounded areas.

Class 0 appliances have plugs that only fit in ungrounded outlets and are only allowed in ungrounded areas. The thinking is that there are two safety barriers: one is the internal single isolation barrier of the appliance, and the other one is the relative inaccessibility of ground in the environment, preventing a closed current path. Such appliances may no longer be legally sold.

Class I appliances may be used in both kinds of areas. In an area with grounded outlets, the protective earthing is relied upon as the second safety barrier, while two-layer safety is provided in exactly the same way as for Class 0 appliances if used in an area with ungrounded outlets.

So basically you are allowed to use an appliance in an area if its plug fits. Of course there might be other restrictions, such as appliances designed for indoor use only.

Can you just design equipment to the lower class I creepage/clearance standards without providing a ground connection in countries like Denmark?

That would be a Class 0 appliance, and selling them are no longer allowed in Sweden. Among other things, it would not be possible (without illegaly modifying the plug or similar) to use such equipment in a modern installation which has only grounded outlets. A Class I appliance needs to have the grounded cord and plug, regardless of where the user is going to plug it in.

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?

Sweden allows equipment designed to the Harmonized European Class I and Class II standards to be sold. There is no additional requirement. The safety of Class I equipment in ungrounded areas is no worse than Class 0 items in the same areas. As for ground impedance, equipment is governed by the same standards. Electrical installations have requirements that the fuse/breaker must trip within a certain time if there is a phase/ground short at the load, setting a limit to how high the grounding impedance may be.

Anyways, I think that for an electronics lab grounding is preferred, even if not having it would at least be relatively safe especially as an RCD is installed. Just as Mike wrote in the second post of this thread, there is a risk of damaging sensitive electronic devices when making connections. The ground connection is also preferable to have to be able to effectively discharge static electricity for ESD protection reasons.

Having your local "ground" floating (usually about 110 V AC due to those mains filters and other capacitive coupling in equipment) also tends to couple hum into high-impedance nodes of circuits being measured/tested. So there is also a signal quality problem.

[megajocke]

While something fishy does seem to be going on (what's the sense in going from having one type of outlet with PE to having the choice between three different ones?), I think most residential installations are TT with the mandatory RCD and adding PE to the outlets should be okay.

That looks like a mess.  Here in Sweden only the leftmost outlet in the picture is used and allowed. I guess we were lucky to use the one that were to become the most common right from the start. The two other types are only used in a few countries (including Denmark) as far as I know.

[westom]

Thor-Arne mentioned that ground wire may be installed and that they just used ungrounded sockets.

  Maybe.  But why?  If the ground wire exists, then why spend the same money for the inferior two wire socket?

  Equipment designed for three wire connections (ie Agilent) contain many layers of human safety.  Eliminating one (ie using it on a two wire circuit) only eliminates one protection layer. The user is still protected.  That is about human safety.

 Second, another factor are stray currents.  Strange currents cause confusion when stray milliamps do not have the common ground to leak away into.  A ground is also important for a more productive working environment.

  Third, that safety (protective) ground does nothing for ESD (a human static electric discharge).  ESD current must have another connection to a different ground.  ESD protection involves other solutions.

[Thor-Arne]

Thor-Arne mentioned that ground wire may be installed and that they just used ungrounded sockets.

  Maybe.  But why?  If the ground wire exists, then why spend the same money for the inferior two wire socket?

I suppose they did that so they could swap the fronts if the customers wanted grounded outlets.
The internals for the socket is the same and can be changed according to the needs. I believe the ones I've seen is the ELKO brand.

I'm not qualified to say what the code say about this, but I wouldn't be surprised it grounding is required in the wall tubing.

[madires]

  Third, that safety (protective) ground does nothing for ESD (a human static electric discharge).  ESD current must have another connection to a different ground.  ESD protection involves other solutions.

I don't agree. The ESD stuff (mat, wristband and so on) is connected via a 1M ohm resistor to PE, the same PE as connected to the power socket. The tip of my ESD compliant soldering station is connected to the PE of the IEC socket via a resistor. At the main mains distribution panel the PE is connected to a proper grounding system (ring armature). All house tubing is also connected to the same ground. There's only one ground!

[westom]

There's only one ground!

  Many grounds exist.  The chassis ground is different from the digital ground, is different from the ESD ground beneath shoes, is different from a floating ground inside a TV, is different from an analog ground, is different from the protective ground, and is different from earth ground.  Some grounds may be interconnected.  Others not.  But numerous and electrically different grounds always exist. 

  Your ESD iron connects to protective (safety) ground for human safety.  It might also perform ESD protection.  But only because of how is connects to the other and relevant ground for ESD protection.

  A benched UUT can be connected to protective ground.  And then be damaged by the resulting ESD discharge.  How?  Follow a complete current loop that is the ESD discharge.  And learn why grounds, even when interconnected, can be electrically different.

[tld]

I'm in a similar situation, also in Norway.

Wiring seems to be fairly decent, but for some reason PE wasn't included in the room where I've set up my lab, and I haven't gotten around to doing anything with it yet.

Estimates for having PE installed there are from $500 up.

Just thought I'd add in that Norway is fairly strict about people wiring stuff up themselves, and there are actually inspection from time to time, to make sure everything is according to code, documentation required that things were done not only by a certified electrician, but by one currently employed with a company, etc.

Funny how that works.  It doesn't actually matter how qualified you are, you're still not allowed to touch it unless you currently do it for a living.

Really funny when you consider that improving crappy work done by such an electrician would be illegal to fix or improve.

I think actually removing a socket to check for issues would be illegal.

- tld

[Thor-Arne]

I'm in a similar situation, also in Norway.

Wiring seems to be fairly decent, but for some reason PE wasn't included in the room where I've set up my lab, and I haven't gotten around to doing anything with it yet.

Estimates for having PE installed there are from $500 up.

$500 isn't too bad, work on electric installations tends to be insanely expensive here.

Just thought I'd add in that Norway is fairly strict about people wiring stuff up themselves, and there are actually inspection from time to time, to make sure everything is according to code, documentation required that things were done not only by a certified electrician, but by one currently employed with a company, etc.

Funny how that works.  It doesn't actually matter how qualified you are, you're still not allowed to touch it unless you currently do it for a living.

Really funny when you consider that improving crappy work done by such an electrician would be illegal to fix or improve.

I think actually removing a socket to check for issues would be illegal.

- tld

You can only touch what is unpluggable, all permanent installations is off limits.

As for checking the wiring one is supposed to call the DLE (Det Lokale Eltilsyn), which is probably going to cost an insane amount of money. And then you have to get a certified electrician to fix any problems they find, yet another insane amount of money.

On the otherhand, I've seen a few bad things done by these certified electricians; entire floors without grounding, wires not properly fixed to the socket, electric meter placed on the wrong circuit (two meters in series), ....

Strange how they can get away with these things.....

[c4757p]

It's almost as if red tape doesn't work....

[madires]

There's only one ground!

  Many grounds exist.  The chassis ground is different from the digital ground, is different from the ESD ground beneath shoes, is different from a floating ground inside a TV, is different from an analog ground, is different from the protective ground, and is different from earth ground.  Some grounds may be interconnected.  Others not.  But numerous and electrically different grounds always exist. 

I thought we're were discussing grounded outlets, so I meant there's one ground for the whole house wired in a star topology. Signal grounds and other grounds inside devices are a completely different story.

  Your ESD iron connects to protective (safety) ground for human safety.  It might also perform ESD protection.  But only because of how is connects to the other and relevant ground for ESD protection.

Since we don't float above the floor and are grounded by our feet or our butt when sitting the best ground for a save ESD potential equalization is the ground of your house, i.e. PE. 

  A benched UUT can be connected to protective ground.  And then be damaged by the resulting ESD discharge.  How?  Follow a complete current loop that is the ESD discharge.  And learn why grounds, even when interconnected, can be electrically different.

Yes, interconnected grounds got differences in their potentials caused by currents and the wire resistance. To minimize those effects a star topology is used. Before touching any insides of the DUT you would equalize your potential via the ESD handwrist (the resistor limits the current, also in case you touch a mains wire) which is connceted to the same ground as the DUT.

[Tepe]

That looks like a mess.  Here in Sweden only the leftmost outlet in the picture is used and allowed. I guess we were lucky to use the one that were to become the most common right from the start. The two other types are only used in a few countries (including Denmark) as far as I know.

The left one is indeed a Schuko outlet like you have (CEE 7/4), the middle one is a CEE 7/5, and the rightmost is a standard Danish grounded outlet (DK 2-1a).

All three are required to be tamper-resistant to you don't go around poking knitting pins or nails into them one at a time.

[Tepe]

It's almost as if red tape doesn't work....

It works. Somebody, somewhere, is making a fortune.

[eKretz]

It's almost as if red tape doesn't work....

It works. Somebody, somewhere, is making a fortune.

Right; it works great for the entities that lobbied for the red tape in the first place, it just puts the screws to everybody else.

[cthree]

Wow, I cannot believe some of the answers coming from so-called "electrical engineers", holy shit!

Hire a licensed electrician to come and inspect your house's wiring and panel. Get an estimate detailing what needs to be done to bring it up to code and then DO IT! It is an investment in your property. It only takes one shock to kill you and you will not see it coming, bam! lights out!

GFCI and arc-fault breakers are a last resort attempt at circumventing the process of your death. If you are lucky, you won't die. Don't bet your life on them. 100mA at mains voltage and you are dead.

Anyone with a "better idea" is a danger to themselves and, more importantly, others. I hope you didn't buy your house from one of them; another reason to get it checked by a licensed professional.

[eKretz]

I'm staying out of this debate. In my opinion there is nothing to debate. Homes and labs should have grounded circuits.

[duskglow]

In staying out of the debate, you just entered it.   

My take on it, from a decidedly hobbyist perspective, is that grounding was created to solve a real problem, and the fact that we're debating this shows that the problem was so successfully solved no one thinks about it anymore.  I know I don't want anything to do with equipment without grounding.

[c4757p]

For me, at least, it's a pretty easy question to answer. You can flap your lips all you want about the safety of floating equipment, but I'll take "I know this is grounded" over "I hope this is floating" any day. Case closed. It's easy to see that something is grounded, it's hard to verify that it's not.

[edavid]

For me, at least, it's a pretty easy question to answer. You can flap your lips all you want about the safety of floating equipment, but I'll take "I know this is grounded" over "I hope this is floating" any day. Case closed. It's easy to see that something is grounded, it's hard to verify that it's not.

Sure, if it doesn't cost anything, but if you have to open the walls, that is a huge hassle and expense, for probably zero benefit

[SeanB]

Different countries, different rules, and they are all correct in their own place.

However the modern consensus is that items must be double insulated such that any single failure which does not prevent it operating as desired will not cause a hazardous voltage to be accessible to the user of the appliance. If this is not possible, or there is exposed metal that is able to be touched, then it must be grounded with a conductor of appropriate cross sectional area to withstand the breaking current of a protective device.

As to the supply side, it is recommended that the conductors must be of appropriate cross sectional area for the current, and that there should be provision for an appliance with a protective earth to have that connected if that is able to be plugged in to the socket.

RCD protection is a good addon if it is not mandatory, and in the USA AFCI is a good recommendation to have in the panels as well as the GFCI. Whether the RCD is in the panel, or in the socket, or the connecting cord is a matter of convention, local regulations and local standards. No one set of rules really covers the whole planet other than equipment has to be safe for the end user to use.

In my country you have to have grounded outlets and you have to have RCD protection on all socket outlets that can take a standard plug in them. You also have to have circuit breakers on each circuit. Fuses are only allowed on older installations untill the house is sold, when you have to upgrade to have RCD and breakers.