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20V AC between slab and electrical ground (lemmy.ca)

submitted 6 days ago by [email protected] to c/[email protected]

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I've just had a new house built in Atlantic Canada. This morning I noticed a bit of a tingle from my coffee machine when I touched it with wet hands. The machine has a grounded (3 pin) plug and I checked - it has 0V between the parts I touched (the entire metal outer case) and the ground socket in the outlet. So, I got curious and did some more measurements. It turns out there is 20V AC (and about 300mV DC) between the ground in my outlets and me when I'm standing on my floor (sealed concrete slab) with bare feet.

I assume this isn't good?

I'll be calling the electrician that wired the house in the morning, but I'd appreciate any insights you might have.

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[–] [email protected] 2 points 5 days ago

Normally, the bonding arrangement should also include a connection to the slab

That makes sense, but I don't have it. My son is an electrician in Australia and he thinks it's a bit strange that I don't have it too.

That the new house is a subordinate structure has a small impact on how the bonding is set up.

No - I'm only sharing water and internet between the buildings. They both have their own feed from the power company.

having 200 ft of conductor means that a distant lightning strike induces a sizable voltage on these wires

I do plan to add surge protectors to both ends. They're so cheap I'd be silly not to.

You may want to re-verify your Ethernet cable using different equipment at the ends

I have tried a few different things, and I think it did connect at 1Gbps once, but didn't stay that way. It did run at 1Gbps when I used it as a fly lead to test it before it was buried. So, unless it was damaged during the back fill, it should work if I can fix the ground issues. The ethernet isn't a big issue for me - it was a bit of an afterthought - a trench was being dug for the water so I bought a cable and dropped it in the trench before it was back filled. I already have a pair of Ubiquiti GigaBeams that work amazingly well - if fixing the ground issues does not fix the ethernet, I'll just keep using the GigaBeams.