Immersion Tripping After New Element

[Arussell87]

Hi all,

I have looked all through the forum but do not see any issues the same as mine and I am just losing the will to live

I have no Gas in the property so we have an Immersion tank on a Modern Digital Timer. Had issues in the past and replaced the element and problem solved.

This time however the Immersion keeps tripping the MCB.

I have installed a new Heating Element and Thermostat and Wiring from the Immersion set up to the Timer using 1.5 Heat Resistant Cable.

I have tested the Element across the terminals and against the tank. I have not however checked with a meter that can push high voltage.

It only trips when the element is on. If the timer box is powered up but not in boost or on mode it does not trip.

Once the element starts up it takes 10-15 minutes for the MCB to trip. The heater is on its own circuit.

Any suggestions?

Many Thanks

 

[Johntheo5]

Are you sure its the MCB its tripping and not the RCD or a RCBO, if its the MCB what is its rating.

 

[Arussell87]

Hey John to be honest I tried to sound smarter than I am. So I have a heater trip then sockets trip then a red trip. The heater and socket ones are smaller on the board and to the left of the one labelled RCD.

 

[Johntheo5]

OK, so what's tripping, is it the (a) RCD, if not, which one is tripping, post a close up photo of your board showing the one that's tripping.

 

[ericmark]

In the main immersion heaters cause the RCD or RCBO to trip due to earth leakage, which is caused either by the immersion corroding or the seals failing, either way only cure is new immersion heater.

Other faults are the thermostat failing, but that will rarely cause anything to trip.

There are three tools used to test for earth leakage faults this one tests the trip, this one tests the element when the trip will not hold in, and this one tests the leakage when it will hold in, looking at around £70, £35, and £35 for testers, so we tend as DIY not to test but just change the immersion heater because the testers cost so much.

 

[Arussell87]

Thanks for the replies.

This is the photo. It is the very left one

 

[Johntheo5]

Thats a 10A MCB, your immersion, if 3kw will draw 13A if it was rated at 230V but the MCB can provide that but will trip eventually, needs upgrading to 16A as long as 1.6mm2 cable is rated for that, will have a look.

 

[Arussell87]

Thanks John. We have lived here 6 years and it did it when the element was knackered previously but after changing it did not trip for years. What would cause it to not be strong enough now?

Thanks so much John

 

[Arussell87]

It is 3kw yes

 

[Johntheo5]

Your supply voltage may have increased and on what the immersion power is based on, you might see 3kw at 240V and 2.75kw at 230V, written on the immersion,if it is based on this then its resistance is 19.2ohms and it would draw 15.6amps at 240V, the UK voltage I think now is nominally 230V so the current draw will be 11.98A and power of 2.76kw, so may be your voltage is running around 240V?

 

[Arussell87]

I have no idea if I am being honest. I would not know even where to start. After you mentioning the RCBO is only 10amps I have done some research and it all comes back the same as what you said. 10amp is too low.

 

[Johntheo5]

Had a look at the type B MCB tripping curve and this will trip at ~ 1.5 times its rating after 15 minutes (your trip time) so 1.5X10, 15amps,
1.5mm2 cable is rated for 14amps if "enclosed in a insulated wall" and 19.5amps "if clipped to a wall), probably OK to increase to a 16A MCB but others on here will advise.

 

[Arussell87]

Thanks for all of your help John. I will await peoples advice and do some more research.