Immersion Tripping RCD

momac1985 · Apr 21, 2014

Hey folks just looking for some info here..
Im after changing my element for my immersion as it kept triping the RCD..
I installed a backer bt7 7" Rod, I wired it the following,
(1)Live to The Element
(2)from the other side if the element I connected it to the L on the immersion
(3)Neutral to the N on the immersion
(4)Earth to earthing point

The problem is it keeps tripping the RCD..I disconnected all cables from the element and I got 240 across L-N & L-E

Its at number 2 above is where my problem is, when I connect from one side of the element to the L on the immersion it trips..if I wired everything else bar connecting that cable it wouldn't trip the RCD..

Any ideas??????

Marvo · Apr 21, 2014

Did the immersion heater used to work okay then just started tripping the rcd? How long does the rcd take to trip? Do you have an insulation tester (mega tester)? Can you post a photo of the connections you've made?

momac1985 · Apr 21, 2014

No don't have a megger! What would that verify?
The RCD trips instantly once you turn on power to the immersion. I changed it about two years ago and its been working fine until last week where it just went again. I changed the Element twice thinking it might have been a faulty element but obviously not!

davesparks · Apr 21, 2014

This doesn't make much sense, from your description you say you have replaced the element but still it trips. So either the supply circuit is faulty, or you are confusing the element with the thermostat.

The thermostat is the short rod which slots in to the stat pocket of the immersion heater. The element is the part permanently fixed to the brass boss.

Depending on what type of element it is then two years is about right. A copper element can give way after a couple of months if the water conditions aren't right.

telectrix · Apr 21, 2014

looks like you have changed the stat. when it's the element that's faulty. the element is the whole caboodle with that huge hexagonal thingy.

[ElectriciansForums.net] Immersion Tripping RCD

Octopus · Apr 21, 2014

Fault in the switch, cable or connections poor at the immersion?

momac1985 · Apr 21, 2014

ok folks i've mixed things up a bit alright

yes its the thermostat i've changed,the short rod thats in the pics below!

telectrix · Apr 21, 2014

prepare to get wet then.

momac1985 · Apr 21, 2014

no fault in connections at switch! I've opened it up and checked everything is 100%. I've disconnected the cables from the thermostat and put them in connector blocks and everthing is ok as far as that. As i said previously, I connected,
Live - Thermostat
From the other end of the thermostat to L on the Immersion
Neutral - to N on the Immersion
And Earth to earth

Also made sure that all connections were tight so I wouldnt say its poor connections!

Hawkmoon · Apr 21, 2014

Seems you need to call an electrician, he will (using appropriate test equipment) test the immersion/circuitry and replace/repair as necessary - you're just running round in circles wasting your time.

Marvo · Apr 21, 2014

momac1985 said:
No don't have a megger! What would that verify?

It would be the right tester to localise the fault. The other option is you just keep replacing parts blindly until you accidentally find the fault but it can get expensive and unnecessarily long winded doing it that way and bear in mind there could be multiple small leakage faults amounting to a total that's over the 30mA RCD tripping threshold.

Hawkmoon · Apr 21, 2014

Picture 2 ???????:whatchutalkingabout

davesparks · Apr 21, 2014

You're a braver man than me if you've changed one of those immersions! That's asking for the copper sleeve it sits in to buckle.

If it trips with the immersion connected and doesn't with it disconnected then I'd say its a fairly safe bet the immersion is kathucked.
Plus 2 years is a reasonable time for it to last if it's a cheap copper one, I've had to change them less than 3 months after some fool has fitted one around here due to the hard water.

As much as I hate to say this but I think just this once I'll say I don't think a visit from an electrician will achieve much more than re-confirming what you already know.

GMES · Apr 21, 2014

As above sounds like your element is Knacked i would get someone in to do the job if you don't feel your up for the challenge.
One of the problem's with element replacement is if you are not careful you can end up cracking the tank when you try to undo the Boss, i have seen this happen many times, then you end up replaceing the entire immersion tank, and as Telectrix said you get very wet.

davesparks · Apr 21, 2014

Look at the pics, it's not in a normal cylinder, it's in one of those copper sleeve/pocket type arrangements.

I'd be even less inclined to do the swap in one of them.