New immersion heater still tripping RCD

[Iain Milligan]

We don't generally use the immersion heater so I'm planning to wire it into a Solic 200.

First - to make sure it is working I removed the old time clock and controlled it direct from the 16A MCB switched spur - 80A RCD tripped.

Isolated the tripping to the immersion heater, as wiring a light into the switched spur caused no tripping.

Today replaced the immersion heater with a new Tesla 3KW and new 32A wire - still tripping the RCD. Measured 19.4 ohms across the element with no measurable leakage to earth or the plumbing.

In fact it is only when the element is powered it trips. When the temp switch is low 20deg C - i.e. element switch off it is fine and power being on does not trip it.

Any thoughts - RCD faulty? - 16A MCB too low powered?

 

[JohnD]

show us photos of the cables and the wiring, please.

Try connecting a kettle to the same circuit. The load will be about the same.

 

[EFLImpudence]

First - to make sure it is working I removed the old time clock and controlled it direct from the 16A MCB switched spur -

What is a 16A MCB switched spur?

80A RCD tripped.

30mA/O.03A RCD tripped.

Isolated the tripping to the immersion heater, as wiring a light into the switched spur caused no tripping.

Ok. Something to do with the immersion and/or its wiring.

Today replaced the immersion heater with a new Tesla 3KW and new 32A wire -

3kW @ 240V is 12.5A.

Measured 19.4 ohms across the element with no measurable leakage to earth or the plumbing.

Should be alright then.

In fact it is only when the element is powered it trips.

Instantly or after a while when hot?

Any thoughts - RCD faulty? -

Not impossible.

16A MCB too low powered?

Nothing to do with it.

 

[RF Lighting]

It is not connected correctly

 

[oldbutnotdead]

What else is protected by the RCD? Pics of the connections? What did you test with- a multimeter? You'd need a Megger or modern equivalent to really check line-earth insulation. And critically was the immersion heater behaving BEFORE you started messing with the wiring?

 

[flameport]

We don't generally use the immersion heater so I'm planning to wire it into a Solic 200

To achieve what?
Paying £200 for a device so you can get a tiny amount of 'free' hot water from solar panels makes no sense.

wiring a light into the switched spur caused no tripping.

That proves nothing - a LED light less than 7W won't trip a 30mA RCD, and even if it was more than that, the fault may be on another circuit and require far more than 30mA on the immersion circuit before it trips.