One for the sparkeys out there (1 Viewer)

[tick59]

When my motorhome is plugged into mains everything is ok ecept when you switch the water heater on then the house electrics blow. Have checked fuses in van all ok only the house electrics affected. ????

 

[Odd job]

Is it the MCB or the RCD that trips?

 

[Spriddler]

The house may have a faster blow breaker than the m/h. Mine has.
I'd suspect a short or fault in the wiring or most likely in the heater element.
If you have a test meter you can use it to check for a fault WITH THE EHU MAINS PLUG REMOVED FROM THE M/H SOCKET - E.G. COMPLETELY DISCONNECTED.

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[BuilderBob]

I agree with Spriddler, the most likely cause is corrosion of the heating element.
I stand to be corrected, but my thoughts are this, There should be two terminals on the heater element fitting, they should be a closed circuit, if you do a circuit test (with the EHU disconnected of course, ) with one probe on a terminal and the other on the metal casing of the water heater, you should not get a circuit, unless, the element is broke, usually with a split in it.

 

[pappajohn]

If its the RCD main switch blowing you have a boiler fault.
If its an MCB tripping it's overloaded.
Is the hookup socket seperate or do you plug into the house sockets?

 

[autorouter]

The RCD is the one with a 'test' button on it. An MCB doesn't have a test button.

If the insulation has broken down on the heater element, and there's leakage to earth from it, then the RCD will trip out. It protects against electric shock.

If the insulation has broken down so that there's a short circuit, and excessive current flow, then the MCB will trip. Either way, it's likely you'll need to replace the heater element.

I'd guess it's an earth leakage fault, maybe there's no RCD fitted in the MH, and the RCD in the house has tripped. Does it have a test button?

It's a good idea to have an RCD fitted to the MH, while you are getting the heater element fixed. Otherwise you are relying on the RCD on the hookup post on a campsite, of unknown dodginess. All modern MHs have an RCD.

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[bigalw35]

You can’t check for earth leakage with a multimeter, you need an “earth fault loop impedance tester”, but as already been mention I would agree the element is probably U/S and requires replacement

 

[gpat]

I'll put money on that you have just overloaded the circuit that your EHU is on. Try an extension into the house and make sure everything in the house is off

If it still trips the switch then I'll agree its the element, if it works ok with that its just too much for the EHU circuit (whatever that is)

 

[bigalw35]

The only way you can rule out the element, one way or the other, is by using an earth fault loop impedance tester, a megger

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[Daniel. M]

By and large the kitchen ring main has the highest load capacity, try plugging the ehu into one of the kitchen sockets, if it still trips then likely to be a fault on the motorhome

 

[68c]

Surely it is still on a plug with a 13amp fuse. I wonder if there is some odd return path through the 12v system that is disturbing the trip. I know using a 240v soldering iron when plugged into the van's 240v socket can give you a belt if you solder onto a live 12v lead. Not sure why, I now always unplug the EHU and use an extension lead when soldering in the van. I dimly remember it may be 120v shock as the 240v mains runs +120v/-120v around the neutral, or something like that.

 

[pappajohn]

Surely it is still on a plug with a 13amp fuse

A 13a fuse will only pop on overload.
That's the reason for domestic consumer units have at least an RCD main switch.... To protect against shock if touching a live wire or faulty appliance where a fuse won't blow. . .

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[Spriddler]

.......only the house electrics affected. ????

I had assumed it was the house main RCD ("house electrics") rather than one particular MCB that tripped.

 

[gpat]

I was just thinking that if I am on a campsite hook up and its only 4a. If i turn on the water heater by mistake it trips the Consumer unit doesn't it?

 

[autorouter]

I dimly remember it may be 120v shock as the 240v mains runs +120v/-120v around the neutral, or something like that.

Domestic circuits are not wired like that in the UK, or indeed in Europe. I believe some circuits in the US are, giving 120V for some appliances and 240V for higher power appliances. Some people, including me, have come across this rarely on Spanish campsites. But almost always, the neutral is at or close to ground, and the live goes +240V/-240V.

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[autorouter]

I was just thinking that if I am on a campsite hook up and its only 4a. If i turn on the water heater by mistake it trips the Consumer unit doesn't it?

It's certainly one of the possibilities. The MCB would trip in that case. That's why we're asking if it's an MCB or RCD that is tripping.

 

[Steve and Denise]

The only way you can rule out the element, one way or the other, is by using an earth fault loop impedance tester, a megger

I would not be to keen on using a megger on anything electronic control or displays.

 

[bigalw35]

Disconnect the element and check between both connections, DO NOT MEGGER LOW VOLTAGE/ELECTRONIC EQUIPMENT !!!

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[RandallC]

AND THE OP

has said what in response to the above?

Sorry why do do folks ask Q's and not say if sorted, still a problem, any more ideas, THANKS!

Guess I'm missing being out and about in the MH, sick as a parrot of it sat there, wasting away.

Think it's "Cabin Fever"

Just to add having replaced the elements in the Truma 6E twice. It's odds on one of the elements has blown and is short to earth.
Has the op checked it works on GAS with electrics off. If no hook-up connected the system cant trip on earth fault or overload.

 

[Silver-Fox]

I believe some circuits in the US are, giving 120V for some appliances and 240V for higher power appliances

It would surprise me if they run 240v for high power appliances.

We run some high power stuff on site and it’s all 110v

 

[stevewagner]

I'll put money on that you have just overloaded the circuit that your EHU is on. Try an extension into the house and make sure everything in the house is off

If it still trips the switch then I'll agree its the element, if it works ok with that its just too much for the EHU circuit (whatever that is)

An RCD does not trip on an overload only an earth fault.

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[bigalw35]

An RCD does not trip on an overload only an earth fault.

You are partially correct, but you can get an RCBO trips out on overload and earth fault current, basically directly swappable with mcb’s

 

[stevewagner]

We had a similar discussion the other day in regard to RCD's in motorhomes. Suffice to say that if the motorhome RCD is 30 milliamp and the supply RCD is also 30 milliamp either one could trip as there is no discrimination. Many campsites have locked electrical enclosures which is a problem when the office is closed.
If the OP leaves the heater off when connecting the EHU and the supply does not fail then clearly the heater is at fault. The easiest way to test the element would be a continuity test (with power disconnected) across the terminals.

 

[stevewagner]

You are partially correct, but you can get an RCBO trips out on overload and earth fault current, basically directly swappable with mcb’s

We were talking about RCD's so I was completely right

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[tick59]

Dont know what a RCD is all i know is the house electrics switch off and the fuses trip.Works ok on gas.

 

[bigalw35]

We had a similar discussion the other day in regard to RCD's in motorhomes. Suffice to say that if the motorhome RCD is 30 milliamp and the supply RCD is also 30 milliamp either one could trip as there is no discrimination. Many campsites have locked electrical enclosures which is a problem when the office is closed.
If the OP leaves the heater off when connecting the EHU and the supply does not fail then clearly the heater is at fault. The easiest way to test the element would be a continuity test (with power disconnected) across the terminals.

That would only tell you if the element had continuity or not IT WOULD NOT TELL YOU IF THERE WAS AN EARTH FAULT

 

[bigalw35]

Dont know what a RCD is all i know is the house electrics switch off and the fuses trip.Works ok on gas.

Residual current device, it trips out (disconnects) when it detect earth leakage

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[stevewagner]

Dont know what a RCD is all i know is the house electrics switch off and the fuses trip.

RCD = Residual Current Device and it is designed to operate under an earth fault condition i.e. neutral to earth or positive to earth, but not neutral to positive (that would be a dead short and would trip the MCB).
Is it just one switch that trips out the complete electrics in the house? If so it should have a small test button on the front.

 

[Spriddler]

Dont know what a RCD is all i know is the house electrics switch off and the fuses trip.Works ok on gas.

To clarify; do absolutely ALL the house electrics go off, e.g. lights and power sockets? In other words there's nothing at all working in the house?

 

[mitzimad]

You can’t check for earth leakage with a multimeter, you need an “earth fault loop impedance tester”, but as already been mention I would agree the element is probably U/S and requires replacement

you may not be able to do the full test but getting a circuit from one terminal to the shell of the tank does tell you there a a break in the element ive been testing immmersions that way for years