RCD keeps tripping but only at home (1 Viewer)

[stuartholmes]

Hi
We have a Murvi Morello PVC and have been using electricity on campsite hook-up without issue except when we overloaded it by using kettle & fan heater simultaneously. (Soon fixed that by turning off the heater while kettling & no probs thereafter.)

But now we're back home & plugged in via same cable to our house 240v supply the RCD keeps tripping all by itself for no apparent reason.

There are no appliances plugged in & the only possible drain I can see is the battery charger and Webasto cabin/water heater. When we're not using it more heavily the former is mainly driven by solar & I've turned the latter to frost protection only, fuelled by diesel, so I can't think either would cause an overload - and anyway, we've used far more without issue while on campsites.

Anyone got any ideas what could be making the difference now we're at home - can it be some sort of spiking from the house? or something to do with the availability of more amps? (or watts?)

All ideas gratefully accepted!! Thank you

 

[autorouter]

In a modern home or motorhome box there are two different types of devices, with different jobs. An MCB protects against excessive current and overload. It trips as you describe, when too many appliances are switched on at once.

An RCD is entirely different. It protects against leakage to earth. It compares the outgoing and returning current flow, and if there's the slightest difference it recognises an earth leakage, and trips. Any difference of more than 30mA (0.03A) causes it to trip.

The idea is that if you touch a live wire, some current will flow through your body to earth, and not back through the RCD. It trips to protect you from electric shock. 30mA is low enough that no harm is caused to you.

However, any other leakage to earth will also cause it to trip. Good candidates are anything likely to get wet. Water inside the hookup plugs, water dripping on any appliance. Other possibilities are heating elements failing and shorting to earth, in the fridge or water heater.

To track it down, first connect the hookup cable to the house without plugging the other end into the MH. If it doesn't trip, turn off both MCBs in the MH box and connect the hookup. If it still doesn't trip, switch on the MCBs one at a time to see which one trips it.

 

[L' Hobo]

I know little about electrics but I do know that some diesel heaters do demand a lot of electric on start-up. Could that be tripping it?

 

[Raul]

I know little about electrics but I do know that some diesel heaters do demand a lot of electric on start-up. Could that be tripping it?

Not a chance, 10A @ 12v it’s 120w, the mains ehu will barely see that.
It’s what autorouter suggested, rcd trips when something has a leakage to earth.

 

[stuartholmes]

In a modern home or motorhome box there are two different types of devices, with different jobs. An MCB protects against excessive current and overload. It trips as you describe, when too many appliances are switched on at once.

An RCD is entirely different. It protects against leakage to earth. It compares the outgoing and returning current flow, and if there's the slightest difference it recognises an earth leakage, and trips. Any difference of more than 30mA (0.03A) causes it to trip.

The idea is that if you touch a live wire, some current will flow through your body to earth, and not back through the RCD. It trips to protect you from electric shock. 30mA is low enough that no harm is caused to you.

However, any other leakage to earth will also cause it to trip. Good candidates are anything likely to get wet. Water inside the hookup plugs, water dripping on any appliance. Other possibilities are heating elements failing and shorting to earth, in the fridge or water heater.

To track it down, first connect the hookup cable to the house without plugging the other end into the MH. If it doesn't trip, turn off both MCBs in the MH box and connect the hookup. If it still doesn't trip, switch on the MCBs one at a time to see which one trips it.

Ah, so the thing I have in the 'van & described as an RCD is actually an MCB ? (see photo ☺)

I plugged in & turned on and nothing tripped.

I didn't think it would let water in but the 'in' socket on the side of the 'van is currently (sic. sorry, no pun intended) not shielded from rain by the flap that hides it when not plugged in. It blew/was sucked off while driving, possibly due to the magnetic catch having un-stuck itself, The replacement is awaiting delivery of new magnets. Be a hoot if that does turn out to be the problem.

Will check again tomorrow & see what overnight brings about. Thank you.

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[autorouter]

Ah, so the thing I have in the 'van & described as an RCD is actually an MCB ? (

One RCD, on the left, with a 'Test' button on it. The leakage trip current is 30mA, but it's written as '0,03A' in tiny writing (those Europeans use a comma for a decimal point instead of a full stop).

And one MCB on the right, double pole so it switches both live and neutral. The 'B13' means if the current exceeds 13A it should trip.

So which one of those is tripping? or is it just the house RCD?

In case you were wondering, the '25A' on the RCD means it is suitable for use in circuits carrying up to 25A. It doesn't do anything if the current is excessive, that's the job of the MCB.

 

[stuartholmes]

I know little about electrics but I do know that some diesel heaters do demand a lot of electric on start-up. Could that be

One RCD, on the left, with a 'Test' button on it. The leakage trip current is 30mA, but it's written as '0,03A' in tiny writing (those Europeans use a comma for a decimal point instead of a full stop).

And one MCB on the right, double pole so it switches both live and neutral. The 'B13' means if the current exceeds 13A it should trip.

So which one of those is tripping? or is it just the house RCD?

In case you were wondering, the '25A' on the RCD means it is suitable for use in circuits carrying up to 25A. It doesn't do anything if the current is excessive, that's the job of the MCB.

Thank you, I feel slightly relieved to have not been entirely stupid/ignorant.

It's only the RCD that trips.

When I 'untrip' it, it's quite content until some unspecifiable time later when I discover it gone again.

'Test' button works as expected.

House RCD unaffected.

(Thanks very much for your help & advice.)

 

[Raul]

It could be that, you already got some current leakage on the house circuit that you are plugging in, plus a bit from the MH when you plug in, and it adds up to trip the house RCD. Or, the house rcd may be tripping to early, tired needs changing. Without proper test and current leakage measurements, it’s hard to guess where is the problem. Sometimes you have devices plugged in without realising that are intentionally leaking to earth for their functionality. A PC leaks to earth 0.4-0.6ma from new. Adding media devices on one circuit can be us much as 3-4ma. You need to find the unwanted leakage.

 

[berni109]

stuartholmes i think the above comments explain what u need to do but without test equipment you can only work through each item separately until you find what's wrong. (Not trying to teach you how to suck eggs).
Switch everything off. House plug (remove hookup) and try boiling a 3kw kettle from it. Switch the rcd and mcb off in van then connect hookup. Switch rcd on and if ok hit the test button and if it works u can switch it on again.
Make sure everything is off in the van then switch one mcb on and if ok switch one thing at a time on. If it trips it's the last thing u switched on if it's good try boiling he kettle in the van. Switch that mcb off and everything in the van and then switch other mcb on and rep process one thing at a time.
Maybe the mcb is double pole as suggested rather than 2 seperate circuits. In which case nothing will work in the van unless they are both on.

 

[autorouter]

First test, nice and simple, is to switch off the MCB (on the right) and see if the RCD still trips. If it does, then there's leakage in/near the motorhome box, or the RCD is failing. If it doesn't trip, but still trips when the MCB is on, then the problem is somewhere past the MCB. Doesn't narrow it down much, but at least you know it's not the RCD failing.

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[stuartholmes]

Well here's an update with the oddest info....

I did the checks & tests & experimented with all the permutations of what to switch on first & what else to have plugged in but everything is (and has been for 48 hours) exactly as 'originally' except that it's stopped tripping!

Obviously not unhappy with that except that it's a bit of a puzzle. My best guess is there was a short somewhere caused by moisture that's now gone away... If so can only hope it stays that way!!

Thanks everyone for the supportive & helpful comments.

 

[berni109]

If u have been out in the rain (especially if it anything like the amount we have had here - will it ever bl00dy stop) it could have been a bit of damp somewhere.
Good it seems to be sorted- fingers crossed.

 

[Treeeev]

Well here's an update with the oddest info....

I did the checks & tests & experimented with all the permutations of what to switch on first & what else to have plugged in but everything is (and has been for 48 hours) exactly as 'originally' except that it's stopped tripping!

Obviously not unhappy with that except that it's a bit of a puzzle. My best guess is there was a short somewhere caused by moisture that's now gone away... If so can only hope it stays that way!!

Thanks everyone for the supportive & helpful comments.

I would suggest that you have identified your problem. As you have lost the flap over the EHU inlet moisture has got into the EHU inlet. If your RCD trips again before you replace the inlet, spray the pins and also the EHU lead socket with WD40 to displace the moisture.

Cheers

Trevor

 

[stuartholmes]

I would suggest that you have identified your problem. As you have lost the flap over the EHU inlet moisture has got into the EHU inlet. If your RCD trips again before you replace the inlet, spray the pins and also the EHU lead socket with WD40 to displace the moisture.

Cheers

Trevor

Thanks, I hope that's all it was. Flap cover back on since yesterday eve . We did have a good rainstorm before then that didn't impinge but can't say it was a desperately thorough test.

Puzzles me a bit though, if that was the problem, why some of the campsite sockets I see don't let water in just as readily.

Guess it'll be like Lord Lucan, we'll never actually know...

 

[Treeeev]

Stuart

I think that when you’re stationary ie at a campsite, the rain runs down the side of the van. When you are driving, you get a fine mist sucked in around the inlet and I think that it’s this mist that has settled in the EHU inlet. I suspect that the RCD detected a slight leak to earth through this dampness and caused it to trip.

Hopefully all sorted now

Cheers

Trevor

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[steve69]

In a modern home or motorhome box there are two different types of devices, with different jobs. An MCB protects against excessive current and overload. It trips as you describe, when too many appliances are switched on at once.

An RCD is entirely different. It protects against leakage to earth. It compares the outgoing and returning current flow, and if there's the slightest difference it recognises an earth leakage, and trips. Any difference of more than 30mA (0.03A) causes it to trip.

I curse "modern technology" at times ,I really do.
10 years ago I had a MCB/RCD or whatever tripped for no obvious reason. So, I switched every appliance off at the socket - as you do - but found the MCB/RCD or whatever switch would not re-set. I called an electrician who came round and straight away started to pull all the plugs out their sockets. "Why are doing that?" I asked. "I've already switched them off".
"Not good enough" he replied. "You have to take all the plugs out with these RCD's." It worked and we found the problem.
So what is the bl***y point in having switches on electric sockets if they are not totally isolating the appliance?
It cost me £100 to find this out.
Technology...PAH!

 

[stuartholmes]

Stuart

I think that when you’re stationary ie at a campsite, the rain runs down the side of the van. When you are driving, you get a fine mist sucked in around the inlet and I think that it’s this mist that has settled in the EHU inlet. I suspect that the RCD detected a slight leak to earth through this dampness and caused it to trip.

Hopefully all sorted now

Cheers

Trevor

That sounds possible, I did drive a few days between having to take the covering flap off and repairing it. (Spotted one the hinge pin on one side completely missing, no idea how but I obviousy wanted to take it right off & keep it safe until I could fix properly.)
Think I'm confident now

 

[stuartholmes]

I curse "modern technology" at times ,I really do.
10 years ago I had a MCB/RCD or whatever tripped for no obvious reason. So, I switched every appliance off at the socket - as you do - but found the MCB/RCD or whatever switch would not re-set. I called an electrician who came round and straight away started to pull all the plugs out their sockets. "Why are doing that?" I asked. "I've already switched them off".
"Not good enough" he replied. "You have to take all the plugs out with these RCD's." It worked and we found the problem.
So what is the bl***y point in having switches on electric sockets if they are not totally isolating the appliance?
It cost me £100 to find this out.
Technology...PAH!

You have my sympathy!! Many years ago when I was a poor student I had to drive my A30 with no windscreen wipers for most of a year because I didn't know it just needed the fuse changing and couldn't afford to get a garage to investigate for me.
Having that hard learned lesson in automotive electronics in mind, when the problem this thread is about arose I went straight to unscrew the panel in back of the wardrobe & one by one checked all 15 fuses before remembering there's a switch on the RCD....