How can there be voltage on water pipes?

[stopconsuming]

Hi everyone,

I need some help with an electrical issue I'm experiencing. I recently created a new circuit for an electric oven at my friend's place, and when I returned home, my friend called to say that the two water pipes connected to the boiler were smoking.

When I arrived, I first measured that there was no voltage in the supply line feeding the boiler (it's on a separate circuit controlled remotely from the rest of the house). However, I measured a voltage of 110V between the neutral wire of the boiler and the water pipes (we use 230V single phase in Hungary, and the pipes are made of iron). I also measured a slight difference in voltage between the two water pipes, which could have caused an arc between them.

Here's what's happening: when the oven is turned on and operated at its maximum load, I measure 110-115V between the water and the neutral wire. However, if only a part of the oven is turned on at a lower load, I only measure 30-35V between them. It's worth noting that the wiring in the house is old and the connections in the distribution box are just twisted together. All of the neutral wires (I counted five) are also twisted, and I didn't undo them. Instead, I cut one of the neutral wires and connected it to a terminal block with the neutral wire of the oven cable.

Tomorrow, after work, I plan to replace the twisted connections of the neutral wires. However, if the problem persists, I'm not sure what to do next. The house has three-phase wiring (one phase is used for the whole house, one for the oven, and one is unused), as well as a neutral wire. The neutral wire is not separated onto a separate protective ground in the meter box, unfortunately, and I can't touch the meter box since only the utility's authorized technician can do that.

I'm afraid I may have done something wrong, so any ideas or suggestions would be greatly appreciated. Thank you!

 

[James]

first thing to do is turn off the power to the house,
swallow your pride and get someone who is knowledgeable in electrics to come look at it.

what you have is dangerous and needs more than a bit of internet advice, it needs a hands on approach from a professional.

sorry to be harsh but if you are seeing smoke from pipes and measuring voltages more than a couple of volts between pipes and Neutral or earth, you have a serious problem that could be fatal.

 

[Dustydazzler]

Smoking pipes and mains voltage on the water pipe is BAD

Needs sorting out ASAP

 

[Lucien Nunes]

The neutral wire is not separated onto a separate protective ground in the meter box,

This is important. On a TN-C system with a combined neutral / protective earth, a broken / high resistance conductor or connection can cause exposed metalwork to become live. You then have the question: What is live? The pipes with respect to the (earthed) neutral conductor, or the neutral conductor with respect to the (earthed) pipes. With TN-C, one false move and you can create a death-trap. Large single-phase loads will show problems up to the greatest extent by creating the highest neutral current.

I appreciate that any problem with the combined neutral / earth is probably not of your making, but as above you would do well not to take on any responsibility for it unless you are fully competent and qualified. It's a much riskier scenario than wiring in an oven to an otherwise intact system.

I would be interested to see pics. Something might be obvious.

 

[littlespark]

You wonder if this issue was there before the additional circuit was added….

Will it be 3ph like UK? Ie 400v between phases and 230 ph-n or is the 110 the expected full voltage

 

[telectrix]

Smoking pipes and mains voltage on the water pipe is BAD

Needs sorting out ASAP

my granddad used to smoke a pipe. did him no harm.

 

[Dustydazzler]

my granddad used to smoke a pipe. did him no harm.

Hi Tel , hope you are well

My old boss used to smoke pipe with Old Clan tobacco in it will at work

You could literally smell it 150 yards away

 

[Lucien Nunes]

Will it be 3ph like UK? Ie 400v between phases and 230 ph-n

Yes, 230/400V throughout. I don't know whether they ever used 230V delta or whether any is still in use today, but that obviously doesn't apply here.