Intermittent Earth Trips

[mav]

Apologies for asking, but I am a total novice when it comes to electrics. I've done a search but can't seem to find any post where people have had a similar problem.

Twice over the past couple of days, my consumer unit has tripped out on the earth switch. It will only reset after I turn off all the MCB's. Likewise, I have to turn all the MCB's off after pressing the test button before it will reset. Any suggestions please.

It may not be connected, but the problem only started the day after Transco replaced my gas meter.

Keith

 

[ban-all-sheds]

Firstly, the fact that you can't reset the RCD without turning off the MCBs first is 100% normal and nothing is wrong.

Secondly, I'm afraid that intermittent problems like this are very hard to track down - can you identify anything that is happening when it trips?

As for the gas meter replacement, I can't see how this is related, unless you had no earth before, and you now have one via newly-fitted main bonding to the gas pipe....

 

[Steve]

Did transco tell you when they changed the gas meter? They seem to have replaced ours, I only discovered it when i went to take a meter reading. Didn't tell us. Good job we have an electronic boiler . . . .

 

[mav]

Did transco tell you when they changed the gas meter? They seem to have replaced ours, I only discovered it when i went to take a meter reading. Didn't tell us. Good job we have an electronic boiler . . . .

Yes they let us know a week or so in advance. Turned up at lunchtime though when we'd got the gas hob on!

Keith

 

[mav]

Firstly, the fact that you can't reset the RCD without turning off the MCBs first is 100% normal and nothing is wrong.

Secondly, I'm afraid that intermittent problems like this are very hard to track down - can you identify anything that is happening when it trips?

The first time was during the night whilst we were in bed. The only things running would have been the washing machine, fridge and freezer. Today, the washing machine wasn't on, but we were up and about, the wife was ironing and we had the tv's, pc's all on.

Keith

 

[plugwash]

fridge and freezer are prime suspects then (large motors, earthed and wet due to condensation on cold parts).

can you temporerolly move them to non protected circuits (e.g. run an extention lead from a 16A breaker in the non-rcd side) and see if the problem keeps happening?

 

[sparky40]

When you say "earth switch" do you mean R.C.D. ? {Or an Earth Leakage Circuit breaker ?} Do you know what type of system your supply is ( tt tncs, tnc.....) ? ..And no mcb's trip, just the main switch ?

 

[Adam_151]

When you say "earth switch" do you mean R.C.D. ? {Or an Earth Leakage Circuit breaker ?}

Some ELCBs were actually RCDs, its only the older voltage (as opposed to current) opperated ELCBs (popular on old TT installs) that are dodgy and should be replaced (well unless the current opperated ELCB [RCD] fails the tests)

 

[Adam_151]

Firstly, the fact that you can't reset the RCD without turning off the MCBs first is 100% normal and nothing is wrong.

Are you sure about that? unless you have a fault that is still there when you come to reset the RCD its definatly not the case in my experience... whether its wise to switch an RCD on with a load connected is another matter entirely [anyone know whether the contacts are rated for that type of thing?]

 

[RF Lighting]

[anyone know whether the contacts are rated for that type of thing?]

I presume the contacts must be rated for DOL switching, as it is acceptable to install an RCD as a main switch.

 

[securespark]

Firstly, the fact that you can't reset the RCD without turning off the MCBs first is 100% normal and nothing is wrong.

Are you sure about that? unless you have a fault that is still there when you come to reset the RCD its definatly not the case in my experience... whether its wise to switch an RCD on with a load connected is another matter entirely [anyone know whether the contacts are rated for that type of thing?]

Yeah, Adam it's perfectly OK. I test these things many times every day, and most of them do this. It can be due to stuff in circuit, or it can be because there is an older style electromagnetic RCD which will only reset if all circuits connected are powered down, or else you have to wait a few ticks before resetting.

 

[mav]

When you say "earth switch" do you mean R.C.D. ? {Or an Earth Leakage Circuit breaker ?} Do you know what type of system your supply is ( tt tncs, tnc.....) ? ..And no mcb's trip, just the main switch ?

Yes, the switch with the test button on. I'm sorry I don't know what type of supply it is.

The consumer unit is a Crabtree SB6000. From left to right, there is a 100A main switch and 3 x 6A breakers on that side. There is then a 63A, 30Ma trip RCCB. Finally there are 2 x 40A, 3 x 32A and 1 x 16A breakers.

The consumer unit was installed when the house was built in 1990. A 32A and 40A breaker were added two years ago by an electrician when we had an extension built.

If it were the fridge or freezer that were faulty, wouldn't they trip out every time?

Keith

 

[JohnD]

that sounds like an old model Starbreaker, with the screw-connected MCBs (not the tongue). Sounds like you have two electric showers on it, or an electric shower and a big cooker.

Intermitted tripping is not unusual, for example:

- fridge or freezer running intermittently due to thermostat

- mice nibbling the underfloor cables when they feel like it

- slight background leakage that is near the tripping current, and occasionally fluctuates over it.

- water getting into an outside socket or lamp when it's raining

Is the Cooker on the RCD?

 

[mav]

that sounds like an old model Starbreaker, with the screw-connected MCBs (not the tongue). Sounds like you have two electric showers on it, or an electric shower and a big cooker.

Is the Cooker on the RCD?

There are two electric showers and yes the cooker is on the RCD.

Keith

 

[JohnD]

The electric cooker might have some leakage on it. I expect it has a big switch it the kitchen, try turning it off there when not in use and see if that helps (if so, you could think about moving it to the non-RCD side of the CU, if you have room). Sorry this will mean the clock stops. Also try unplugging the washing machine.

Is the 16A breaker for the immersion heater? If so, try turning that off at its switch too. They sometimes get leakage as they get old, and yours appears to be on the RCD side.

You could also try turning off one circuit at a time, on the MCB at the CU. You may be lucky and identify that one of them is the source of your problems. If so you could then go round unplugging your appliances, one at a time.

Do you have vacant positions on the non-RCD side? I can't remember if that model of CU is easy to reconfigure.

It may be you have a single device or circuit with leakage on it; or it may be you have a number of small leakages that cumulatively approach the trip level. You might be able to identify a faulty appliance with a bit of tinkering as described, if not, you will need an electrician to search it out. Intermittent trips can be quite difficult to find.