Earth leakage on high loads

[meerkatmag]

I'm new to this forum so apologies if this is in the wrong place. I'm a DIYer, not an electrician. I have had electricians out to look at this issue and they have failed to explain the problems so I've been looking into it myself.

My house has 2 rings, one is very large and covers almost all the plugs in the house, the other is just the kitchen. With the house on as normal, usual devices on and normal day to day running, the earth leakage is very minimal, in the range of 5ma to 10ma in total across the whole consumer unit. However if someone plugs a high load device in, such as a hairdryer or toaster the earth leakage jumps right up to 30ma or 40ma. Sometimes this will trip the RCD, sometimes it doesn't.

We have a computer setup in our loft office with various peripherals, speakers/monitors etc. If we turn all of this on at once a multi plug it almost always trips the RCD. The load when everything is on is minimal, like 2 or 3 amps. But when we turn the plug on the power supplies draw quite a bit of current momentarily and this is enough to trip the RCD pretty much every time. If we switch each peripheral on one at a time slowly the RCD doesn't trip and everything is fine.

If you're wondering how I know the leakage current, I purchase an earth leakage clamp meter and I have a clamp ammeter as well so I've been monitoring both across the two RCDs in my consumer unit. The earth leakage spikes happen across both of my rings, so if I run a kettle on either ring I get a 20ma approx spike which ever ring I plug it into.

If anyone has any ideas I would be very grateful, it's extremely annoying! If you need further info please let me know.
Magnus

 

[mainline]

I'm new to this forum so apologies if this is in the wrong place. I'm a DIYer, not an electrician. I have had electricians out to look at this issue and they have failed to explain the problems so I've been looking into it myself.

My house has 2 rings, one is very large and covers almost all the plugs in the house, the other is just the kitchen. With the house on as normal, usual devices on and normal day to day running, the earth leakage is very minimal, in the range of 5ma to 10ma in total across the whole consumer unit. However if someone plugs a high load device in, such as a hairdryer or toaster the earth leakage jumps right up to 30ma or 40ma. Sometimes this will trip the RCD, sometimes it doesn't.

We have a computer setup in our loft office with various peripherals, speakers/monitors etc. If we turn all of this on at once a multi plug it almost always trips the RCD. The load when everything is on is minimal, like 2 or 3 amps. But when we turn the plug on the power supplies draw quite a bit of current momentarily and this is enough to trip the RCD pretty much every time. If we switch each peripheral on one at a time slowly the RCD doesn't trip and everything is fine.

If you're wondering how I know the leakage current, I purchase an earth leakage clamp meter and I have a clamp ammeter as well so I've been monitoring both across the two RCDs in my consumer unit. The earth leakage spikes happen across both of my rings, so if I run a kettle on either ring I get a 20ma approx spike which ever ring I plug it into.

If anyone has any ideas I would be very grateful, it's extremely annoying! If you need further info please let me know.
Magnus

Have the ring finals been tested properly.

 

[Avo Mk8]

Just thinking aloud - could this suggest a spurious (maybe capacitative?) connection between N and E somewhere on the load side of the CU?
If all the computer setup is off and unplugged (eg to disconnect all the EMI filters in the equipment), does the kettle test still give the same value spike?

I have to say the effect of turning on all the technology simultaneously via an extension block, leading to tripping an rcd is not unexpected behaviour!

PS The allowable tolerance in tripping current of RCD's is -50%, so one tripping at 15mA is still within spec. If your background leakage is already 10mA, that is not really 'minimal'

 

[meerkatmag]

I'll try that check and report back. With all the computer equipment off I'll check if the kettle still causes the leakage.

We get quite a bit of leakage even with just the lighting circuit on. Every circuit seems to add to it.

On the question about circuit testing. When we had an electrician look at this many years ago he tested everything (I believe) and said that he couldn't find anything wrong and just blamed the devices we were plugging in.

Also to note that the leakage happens on either ring, the small kitchen one and the large one. It's a 4 story victorian house so quite large distances on the big ring.

Probably unrelated but I get a 30ma current through my gas pipe and this is earthed to my cu.

 

[meerkatmag]

Right now with no computers on, no tv. Just washing machine, lights, fridge etc. This is 3.3amps draw There is 14.2ma leakage.

If I put kettle on it jumps to 22.6ma

 

[mainline]

Right now with no computers on, no tv. Just washing machine, lights, fridge etc. This is 3.3amps draw There is 14.2ma leakage.

If I put kettle on it jumps to 22.6ma

What is the earthing arrangement ?

Is it just the 2 rings, or does the lighting circuits do the same.

 

[meerkatmag]

What is the earthing arrangement ?

Is it just the 2 rings, or does the lighting circuits do the same.

There's 2xrcds. Left rcd has kitchen ring. Right rcd has main ring and lighting. We also have a car charger which has its own separate cu.

It looks like the earth line from cu goes to a box by the meter and here it's connected to an earth wire from the gas pipe and a wire that goes into the ground under the floor.

 

[mainline]

There's 2xrcds. Left rcd has kitchen ring. Right rcd has main ring and lighting. We also have a car charger which has its own separate cu.

It looks like the earth line from cu goes to a box by the meter and here it's connected to an earth wire from the gas pipe and a wire that goes into the ground under the floor.

I would get a decent electrician in to do some testing.

You could have a neutral to earth problem, but without test results it's all guesswork.

 

[Avo Mk8]

Right now with no computers on, no tv. Just washing machine, lights, fridge etc. This is 3.3amps draw There is 14.2ma leakage.

If I put kettle on it jumps to 22.6ma

But the kettle could be responsible for a real ~8mA earth leakage!?
Bit of a fiddle to measure it at the kettle, but could be done!

 

[meerkatmag]

But the kettle could be responsible for a real ~8mA earth leakage!?
Bit of a fiddle to measure it at the kettle, but could be done!

I'll try to measure it!

 

[meerkatmag]

But the kettle could be responsible for a real ~8mA earth leakage!?
Bit of a fiddle to measure it at the kettle, but could be done!

I modified an extension lead so I can clamp the line and neutral. Kettle did show around 8ma leakage slowly rising to 10ma then dropped to 0ma once it boiled. I'm going to try this in another house and see if this is the kettle or my house wiring.

 

[Avo Mk8]

I modified an extension lead so I can clamp the line and neutral. Kettle did show around 8ma leakage slowly rising to 10ma then dropped to 0ma once it boiled. I'm going to try this in another house and see if this is the kettle or my house wiring.

Useful check - thanks!
I'd bet on the kettle!

 

[mainline]

Useful check - thanks!
I'd bet on the kettle!

One leaky appliance isn't going to cause problems on the other rcd.

 

[James]

Classic Earth to Neutral Fault symptoms.
has anyone checked for it?

 

[mainline]

Classic Earth to Neutral Fault symptoms.

As #8

has anyone checked for it?

He's only got a clamp meter