Dishwasher shock - what test would isolate issue?

[dishman]

I manage a property that has some appliances in situ.

Ironically I was having another machine (washer dryer) repaired under warrantee when the engineer mentioned he got a shock on a separate appliance (dishwasher).

After testing the earth on it he concluded he could detect nothing was wrong. We therefore assumed it must have been a static shock perhaps.

To be doubly sure we got the appliance pat tested, which showed no issues on the appliance.

However, since then the occupier is still reporting getting shocks from the appliance.

I am at a loss. The appliance is no more than a few years old and no issues were mentioned until the engineer who was there to fix another machine got this wayward shock.

If the device checks out, is there something downstream of the machine that could be generating a shock?

What other checks would be appropriate.

Thank you in advance for any replies.

 

[BS3036]

Was the socket correctly earthed?

 

[JohnD]

You have an earthing fault.

It might not be on the appliance or its circuit, it could be you are standing on a damp floor or touching a metal sink that is live.

Look for a local electrician who is a member of a Competent Person Scheme (you can look them up) and preferably also recommended by someone you know zbd trust.

Do not use an advertising website where readers pay to be listed, even if it masquerades as a Recommended or Trusted website.

 

[ericmark]

I know my PAT testing machine tests the supply and will not work if there is a fault on the supply, but not all do that, need another meter to measure the earth loop impedance.

However shock means difference in the voltage between to items, so could just as easy be the sink at fault.

How long ago was the EICR done? And was any work done to correct faults? Although the RCD should trip at 30 mA it will not detect between a TN-C-S earth and true TT earth.

So lack of earth bonding can result in a shock.

So only way is to test, and test equipment is too expensive for DIY only way is use an electrician.

 

[dishman]

EICR was done in February this year.

Board was updated to all RCOBs. No faults found but decided to update the board anyway as it was only a few circuits (small flat) and there was no RCD protection prior.

Since then we have had a lot of odd electrical appliance failures, I have posted about them here. But the consensus was that it was unlikely to be related to the board change and it was just poor timing.

The dishwasher is not located near or next to the sink. So there is unlikely to be any related contact between the two.

 

[JohnD]

However, you have an earth fault and you need a competent electrician to trace and fix it.

You have said there have been multiple shocks so you are aware of the problem.

So far, the shocks have been non-fatal.

 

[JohnD]

Please forward this link to the occupier

https://www.electricalsafetyfirst.org.uk/guidance/advice-for-you/tenants/

 

[dishman]

However, you have an earth fault and you need a competent electrician to trace and fix it.

You have said there have been multiple shocks so you are aware of the problem.

So far, the shocks have been non-fatal.

Oh of course, as soon as this was reported, I looked into resolving it. Thus far no issue has been found. I can only go by the tests that have been done thus far, and they have all come back fine.

Getting further tests is my next step, hence I was wondering, based on the experience here, what should be focused on, so I have at least some idea what I should expect an electrician to check.

 

[bernardgreen]

I am at a loss. The appliance is no more than a few years old and no issues were mentioned until the engineer who was there to fix another machine got this wayward shock.

To get a significant shock there has to be two (or more) points of contact with the body and these points of contact must be at different potentials to each other.

For a person to get a significant shock from the dishwasher they have to be touching something else. It might be that the dishwasher is not faulty and is correctly Earthed and something else that can be touched is Live. This could be a damp floor made Live by a cable fault or faulty appliance. Walking on a damp Live floor will not give a person a shock until they touch something that is Earthed.

Birds can perch on 11kV over head cables because both feet are on the same wire and therefor at the same potential.

 

[ETAF]

just a thought , as mentioned , is there any chance it is static , any flooring changed?
i changed a mat once and got shots all the time, ended throwing it away - cheap nylon thing.....
may have nothing to do with your situation , just a thought

 

[Harry Bloomfield]

It could be the other way around - that the dishwasher is properly earthed and another item they are touching simultaneously is in fact live.

 

[dishman]

hmm, good points. The floor is lino and concrete, and it is a top floor apartment, so certainly not damp. The only other items near by are the washing machine which was recently checked and repaired. It was also pat tested after this shock was reported.

Static was something that we assumed at first. But if they are reporting a shock, it's not something we can ignore or just put down to static without excluding everything else first.

This shock was not noticed until the engineer who repaired the washer/dryer seemingly got one. Only since that time has it been noticed and not for the last 7 months prior.

So based on that, it's something that has only suddenly occurred in my view.

As per above, that engineer checked the appliance and found nothing amiss, and the pat test since has concluded the same.

 

[johnny2007]

Check that the earth in the socket has not come loose.

 

[dishman]

Check that the earth in the socket has not come loose.

I was wondering in the back of my head if that could possibly be something to get checked.

 

[johnny2007]

I was wondering in the back of my head if that could possibly be something to get checked.

I had the same issue a few years ago and my electrician over the phone told me to check that.
The machine is still in operation.