RCD tripping immersion heater.

[James Sutton]

Hello All

A friend of mine has just had a CU change from an old re wireable fuse box to a new Dual RCD board i didnt do the job for him someone else did.

with the old board in place the immersion heater 3Kw worked now with the dual RCD board the immersion heater trips the main RCD the immersion heater runs though a timmer and is supplled by a 20A radial in a swiched fused spur with a 13A fuse

I thought this was to boarder line as 3Kw will pull 13A i would be looking to run off the radial a 20A DP switch.

Could it be that the 3 Kw element is slightly breaking down a is sensitive enough to trip the RCD.

Havent looked at the job just going by what ive been told.

Any thoughts

JS

 

[Octopus]

Take the cover off the immersion heater where the cables are connected to the element. Many years of heating up does nothing positive for the insulation.

Had this exact issue this week when doing functional testing after a CU change.

13A FCU is normally OK for an immersion heater.

 

[MarkieSparkie]

Usually one of two likely causes:
1) Poor termination of the the cable ends, usually the neutal connection leading to insulation burn-back. Remake the terminations after stripping back any conductor that has suffered. Crimp ring terminals to the neutral and cpc ends helps get tight connections.
2) IR test the element between line and cpc terminals, if <2M ohms replace element.

 

[telectrix]

99% it's the element. as markie says. IR the element.

 

[meego]

If all else fails replace the heater or take it off rcd, just earth the thing well

 

[nickblake]

ium going to say as Telex itrs the element they can be funny things if you get the slightest of moisture in the element then this can cause insulation failure what happens is the watter attacks the metal element causing very small holes in which dampness gets in although it would have worked with the 3036 rewireables , but with /RCD's they monitor for imbalances IE moisture between the cunductors within the insulation causing an imbalance , do an insulation test ,check element continuity then from one of the terminals of the heater to the earth connection and ill bet you its less than 2 meg ohms , dont remove it from the RCD thats the whole idiea of protecting the house with an RCD extra saftey find the fault and be safe !