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

[Sherlock Holmes]

Hi, there's no earth ground in my plugs at home. Driving a stake into the ground is not an option and nulling in the box outside is not allowed.

If this is what you had to work with:

1) How would you connect test gear and power supplies that ought to be grounded to earth? What would you do with their chassis grounds?

2) What are some practices you'd adopt around handling static sensitive components from the moment they arrive in the post?

3) Are there some types of projects you wouldn't do in this earth-deficient "lab", like mains connected power amp repairs?

My concern is the safety of my components, my gear, and myself. I have a relatively nice power supply and oscilloscope, and I'm in the market for a good function generator, but I'm not sure how much I should try to do here. Failing logic ICs I can handle, but I'd be sad to see any of my gear blow up.

I mostly play around with breadboards and the occasional PCB. My main interest is basic battery powered amplifiers, CMOS logic, playing around with MCUs. For a year I haven't had anything fail on me so I wonder how much is theory and how much is practice.

Thanks!

Well there likely is an earth of sorts. The neutral is (effectively) connected to ground, the ground (at the substation and at the local address). But the ground/earth wiring is meant to be distinct from neutral, and have the capacity to endure large currents in the event of short circuit faults.

In a situation like you describe, I wonder whether it would be prudent to connect your equipment not to the wall outlets, but to a 1:1 isolating transformer (which eliminates galvanic current flow to the outside electricity system).

Then, if you were standing on the floor even wet floor in bare feet, you'd not get a jolt if you did accidentally touch a metal exposed part of equipment that had accidental come into contact (internally) with the "live". No current could flow "to ground" in such a setup, so its safe. (So long as the equipment itself has no exposed metal that could ever come into contact with live internally).

I was thinking of getting something like that myself for repair of some old tube radios I have here, a simple 1:1 ratio isolating transformer.

Another advantage of isolation too, is that transformers have a very high impedance to HF signals, noise and spikes so you'd be reducing any of that getting through to your equipment.

[Sherlock Holmes]

Hi, there's no earth ground in my plugs at home. Driving a stake into the ground is not an option and nulling in the box outside is not allowed.

If this is what you had to work with:

1) How would you connect test gear and power supplies that ought to be grounded to earth? What would you do with their chassis grounds?

2) What are some practices you'd adopt around handling static sensitive components from the moment they arrive in the post?

3) Are there some types of projects you wouldn't do in this earth-deficient "lab", like mains connected power amp repairs?

My concern is the safety of my components, my gear, and myself. I have a relatively nice power supply and oscilloscope, and I'm in the market for a good function generator, but I'm not sure how much I should try to do here. Failing logic ICs I can handle, but I'd be sad to see any of my gear blow up.

I mostly play around with breadboards and the occasional PCB. My main interest is basic battery powered amplifiers, CMOS logic, playing around with MCUs. For a year I haven't had anything fail on me so I wonder how much is theory and how much is practice.

Thanks!

I'd also like to ask, can you share some photographs of this? of these outlets and any related parts like the breaker boxes or fuse boxes? you might well have a truly historic setup here that would be worth documenting, once its ripped out and updated that history will be lost.

I recall as a kid in Liverpool our house had little well made (dovetail!) wooden boxes mounted on each floor, above a door. When we unlatched the door we'd see these large ceramic user-repairable fuses, all gone now).

[Sherlock Holmes]

240v mains>>1:1 isolation transformer, of desired KVA.

We floated our entire benches and lab that way to safely design and debug KW SMPS and electronic ballasts

Never had any problems

Search for 240/240V isolation transformers

Jon

I've read that many "isolation transformers" actually connect one side of the secondary winding to the incoming ground/neutral (internally) this makes no sense to me.

[bottledwater]

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.

Very interesting, thank you! Do you know why two are you required? I've been assuming just one.

[bottledwater]

In a situation like you describe, I wonder whether it would be prudent to connect your equipment not to the wall outlets, but to a 1:1 isolating transformer (which eliminates galvanic current flow to the outside electricity system).

Then, if you were standing on the floor even wet floor in bare feet, you'd not get a jolt if you did accidentally touch a metal exposed part of equipment that had accidental come into contact (internally) with the "live". No current could flow "to ground" in such a setup, so its safe. (So long as the equipment itself has no exposed metal that could ever come into contact with live internally).

I was thinking of getting something like that myself for repair of some old tube radios I have here, a simple 1:1 ratio isolating transformer.

Another advantage of isolation too, is that transformers have a very high impedance to HF signals, noise and spikes so you'd be reducing any of that getting through to your equipment.

I can't say I understand the details of running the whole bench on a 1:1 isolation transformer. I looked into it a bit because other people in this thread suggested it. It seems it would make me safe but the gear I have is still spec'ed to need a connection to earth ground, to protect itself and for noise and whatever else, and the transformer doesn't provide that, and then I run into having the floating grounds in my gear float to arbitrary levels.

So I decided to have another go at getting an actual earth installed. Fingers crossed it can be done and that it won't cost a fortune.

Btw for anyone else finding this thread, I found this video on isolation transformer safety helpful

I also watched this video