Do's and don'ts in home lab with no earth ground

[TimFox]

but if you take an electrical appliance and drop it into a bathtub with water in it, some current will flow from the line through the water back to the ground connection at the substation,

But will that current be enough to operate an rcd? If the bath is on a wooden floor and all the pipe work is plastic can you be certain the loop impedance is low enough for 30ma to flow without the potential rising above 50v to earth (uk rules)

The US requirement for a GFI in a bathroom is to trip at 6 mA, and not to trip at less than 4 mA.
30 mA seems far too high a trip point, especially in 240 V countries, but maybe that spec is for a whole building?
US code requires a GFI built into any outlet in a bathroom or similar location.

The US television program "Mythbusters" did a show about dropping an appliance into a bathtub, a common trope on criminal/mystery TV shows.
They could not purchase a hairdryer without GFI (even at junk stores), so they had to use a simulacrum.
They found that without a GFI, a lethal current could flow through their dummy, but that the GFI would trip.
https://mythresults.com/episode19

[bdunham7]

As far as I understand, this may bring me to half the line voltage due to the caps in the power supplies, so if I touch anything that's actually earthed, I could be in trouble. There was also a comment that the fuses on my gear won't protect it if there's no real earth connected.

Should I create an unconventional earth connection by connecting to a metal pipe?
Here, the suggestion is to at least put a current-limiting resistor in between. But I could also be charging pipes going elsewhere in the building.

Having your ground connections float up due to Y-caps is a real issue if you truly have no ground.  However, fuses are not really an issue.

It's hard to advise you because almost all alternatives have potential    drawbacks.  Even if you find a nice pipe or something to ground on, unless you have some way of knowing that it has reliable low impedance to actual earth (the one that your supply is referenced to) you run a real risk of some problem in your lab creating a dangerous situation where metal things in your house that should be at ground are actually energized.  OTOH, letting your grounds float isn't really desirable either.  I'd suggest both running a wire to the best ground you can find and using an isolation transformer for your entire lab.  However, I'm sure someone will jump in and point out that this defeats your RCD protection, which is true but unimportant in my view (but that's an ongoing argument I don't want to revive here).  Note that this is not 'floating' anything as the ground between all of your instruments and hopefully an actual ground is still intact. 

Essentially in your case a whole-lab isolation transformer is a tradeoff between not having RCD protection on things you have apart in the lab and leaving the risk that an issue in your lab could result in energizing your plumbing or whatever you've chosen as a ground.

[paulca]

2) Should I create an unconventional earth connection by connecting to a metal pipe?

If you have metal drain pipes, they will make pretty good earth grounds.  Copper supply pipes can be good, but if you don't have access to a real earth it may not be possible to test them properly.

If they aren't grounded of course they are just big antenna and I wouldn't want to be in the path between them and ground... or anywhere near it in a lightening storm.

[BillyO]

If they aren't grounded of course they are just big antenna and I wouldn't want to be in the path between them and ground... or anywhere near it in a lightening storm.

I honestly cannot think of a situation where drain pipes would not eventually be buried in the ground.  I guess a builder could go the all the trouble of making some sort of isolated chambers/tunnels to suspend their drain pipes in until they connected to the main concrete sewer, but that seems a little insane.  Especially in a residential situation.

[bdunham7]

I honestly cannot think of a situation where drain pipes would not eventually be buried in the ground.  I guess a builder could go the all the trouble of making some sort of isolated chambers/tunnels to suspend their drain pipes in until they connected to the main concrete sewer, but that seems a little insane.  Especially in a residential situation.

There could be a nonconductive section or coupler somewhere...

[themadhippy]

I honestly cannot think of a situation where drain pipes would not eventually be buried in the ground. 

buried in the ground aint the problem,but plastic pipes that are very common for drain pipes in the uk dont conduct very well,nor does the ceramic pipes often found on large main drains

[TimFox]

Plastic pipes used for drains are very common nowadays.
Usually PVC, since the required glue joints work well.
However, the liquid contained in them should be somewhat conductive.
Moral:  historical improper grounding should be replaced by proper grounding.
(In high-school competitive debate, we always defined "should" as "ought to, but not necessarily will".)

[BillyO]

There could be a nonconductive section or coupler somewhere...

True.  That would have to be pretty much in the house though.  You don't need much length of a 3" or 4" pipe to be in contact with the ground to make a good earth.  10' would be plenty and give about 1500 sq. in. of area for a 4" pipe  or 1100 sq. in. for a 3" pipe.

[BillyO]

buried in the ground aint the problem,but plastic pipes that are very common for drain pipes in the uk dont conduct very well,nor does the ceramic pipes often found on large main drains

That's why I specifically said "metal drain pipes"

[paulca]

If they aren't grounded of course they are just big antenna and I wouldn't want to be in the path between them and ground... or anywhere near it in a lightening storm.

I honestly cannot think of a situation where drain pipes would not eventually be buried in the ground.  I guess a builder could go the all the trouble of making some sort of isolated chambers/tunnels to suspend their drain pipes in until they connected to the main concrete sewer, but that seems a little insane.  Especially in a residential situation.

Why would you connect a roof drain to the ground?  Most them empty out onto a gutter or some form.  Including the metal ones.  The only down pipe that goes under around here is the "soil stack".

[BillyO]

Why would you connect a roof drain to the ground?  Most them empty out onto a gutter or some form.  Including the metal ones.  The only down pipe that goes under around here is the "soil stack".

?

Roof drain?  Maybe I'm being punked here, but no roof drain.  I was referring to the septic (sewer, black/grey water, shower/tub/basin/toilet) water drain, indeed the "soil stack".  Why would you assume roof drain?

BTW, I do collect mine in a pipe that goes down to the creek near my house.  The pipe is plastic though.

[langwadt]

but if you take an electrical appliance and drop it into a bathtub with water in it, some current will flow from the line through the water back to the ground connection at the substation,

But will that current be enough to operate an rcd? If the bath is on a wooden floor and all the pipe work is plastic can you be certain the loop impedance is low enough for 30ma to flow without the potential rising above 50v to earth (uk rules)

The US requirement for a GFI in a bathroom is to trip at 6 mA, and not to trip at less than 4 mA.
30 mA seems far too high a trip point, especially in 240 V countries, but maybe that spec is for a whole building?
US code requires a GFI built into any outlet in a bathroom or similar location.

there is a single GFI for the whole house/ apartment

[bdunham7]

there is a single GFI for the whole house/ apartment

Wow!  The whole house goes dark?!?  And then you have to figure out where the fault is?

We have per-circuit AFCI (combination) breakers where needed and where GFI is required, at least one per circuit (typically the first wall socket in a chain).  I don't even chain them, I use one GFI per socket location so that when something trips it I know what it was.  That and I have some old wiring that may leak a bit on damp days.

[themadhippy]

Wow!  The whole house goes dark?!?  And then you have to figure out where the fault is?

yep great fun,especially if its a neutral-earth fault.

In the uk we've slowly gone from no rcd protection to   either the whole board protected by 1 device or  split boards were part of the installation is  protected by an rcd and the rest,normally lighting circuits, aren't, and are now moving   to individual circuits having there own rcd.Coming to a dis board soon,if the iee get there way will be afd's,either whole board protection,or individual circuits,combined mcb/rcd/afd's are available,at a price

[BillyO]

...  protected by an rcd and the rest,normally lighting circuits, aren't ...

Here in Canada it is not usual to have the lights on different circuits from the outlets.  There is no law against it, it's just not done but it makes great sense.  If I ever build another house I will sperate the lights from the outlets.

As for GFIs, we are only required to have them on:  Bathroom outlets, outdoor outlets, whirlpool bathtubs and hot tubs.

[Handskemager]

Not home at the moment but pretty sure we have 2x 13 amp fuses (1 for light and 1 for outlets), RCD (can’t remeber the wiring atm) and 16 amp fuse for “kraft stik” (3 phase 400v) for oven and stove.

Living in a 91 spuare meter apartment in Denmark.
Earth protected outlets in the bathroom and kitchen only.
Building is from 1967

[SL4P]

OP, does your GFI have a TEST button?
Problem solved… if that button works, there is a mains earth on the bavpck of the GFCI.

[langwadt]

OP, does your GFI have a TEST button?
Problem solved… if that button works, there is a mains earth on the bavpck of the GFCI.

ehh no, the test button just puts a resistor between live after the GFI and neutral before the GFI

[themadhippy]

OP, does your GFI have a TEST button?
Problem solved… if that button works, there is a mains earth

The test button causes an imbalance by putting a load across the input side and output side so will still work   regardless of  earth.

[langwadt]

Not home at the moment but pretty sure we have 2x 13 amp fuses (1 for light and 1 for outlets), RCD (can’t remeber the wiring atm) and 16 amp fuse for “kraft stik” (3 phase 400v) for oven and stove.

Living in a 91 spuare meter apartment in Denmark.
Earth protected outlets in the bathroom and kitchen only.
Building is from 1967

same, building from 1898, electrical installation from sometime in the early 70's

[bottledwater]

I have two different electricians coming later in the week to see if they have some creative ideas to get earth in..! 

[CatalinaWOW]

I have two different electricians coming later in the week to see if they have some creative ideas to get earth in..! 

With all due respect to the electrical trades, be cautious about what they suggest.  Make sure it makes sense to you, and lines up with all of the cautions identified in this thread.  While there are many excellent electricians, only a few can deal with situations that are off the beaten path.  And unfortunately there are a significant number that don't know their own limitations.

[bottledwater]

I have two different electricians coming later in the week to see if they have some creative ideas to get earth in..! 

With all due respect to the electrical trades, be cautious about what they suggest.  Make sure it makes sense to you, and lines up with all of the cautions identified in this thread.  While there are many excellent electricians, only a few can deal with situations that are off the beaten path.  And unfortunately there are a significant number that don't know their own limitations.

Note taken, thank you. It's part of the reason I'm asking two, maybe three.

Since we most likely can't drill the stake down the basement floor (due to risk of hitting ground water), a specific concern I have is if I'll get a proper earth ground connection if we just put it down a few meters out, next to the basement, if that makes sense. Will it be deep enough and far enough away from the foundation of the building.

I think there's an earth ground connection over in another part of the building that we could try to find to check against. Haven't been able to find it myself. Otherwise, I guess we can at least check the potential difference between neutral and the earth ground we can get, since neutral is supposed to be earth ground referenced at the power station.

[Ian.M]

If your electricians are any good, they'll know how to put in temporary test ground rods and how to use them to measure the effective ground resistance of any ground rod they install.  The only thing that could make that impractical is if the building is surrounded by a large area of concrete or thick tarmac with absolutely no access to the underlying soil anywhere nearby.

[BillyO]

if I'll get a proper earth ground connection if we just put it down a few meters out, next to the basement, if that makes sense. Will it be deep enough and far enough away from the foundation of the building.

Yes, you should.  Here in Ontario Canada I had to put two 10' ground rods into the ground not more than 2 feet from the foundation for my service installation and they had to be connected to the panel with a #6 AWG stranded bare copper wire.  I don't recall if there was a specification for how far apart they had to be.  The ground I put in for my lab is pretty much the same.  I just used re-bar for the rods.  A bout .5m from the foundation (basement).

Edit: found it in a book:

ROD ELECTRODES:

Two manufactured rod electrodes must be installed. Each rod must be at least 3 m long as required by CSA C22.2 No. 41. Each rod must be driven into the earth to its full length, spaced no less than 3 m apart and bonded together by a copper grounding conductor.

BTW:  Meatal pipes, both supply and drain are acceptable as grounds under the Canadian Electric Code.  Your country may have different rules.