Underfloor heating RCD tripping

[abzee]

Hi

I have a Heatmiser UFH on two floors.
One of the floors - UFH8 - RCD is tripping.

First I just replaced the 5A fuse in Heatmiser UHF8- did not work - as it tripped immediately.
I removed the power from Grundfos UMP3 - and placed the 5A fuse and again it tripped.
I removed all the neutral wire(blue) going into the Heatmiser UHF8 from the manifold actuator, placed the 5A fuse, and again, it tripped.

so, I'm not sure if it's the Heatmiser UHF8 PCB or something else.

Any help is appreciated.
Thanks.

 

[ericmark]

I test with a clamp on ammeter, I would guess wrong neutral somewhere, but how to find where not so easy without some test gear.

 

[abzee]

I test with a clamp on ammeter, I would guess wrong neutral somewhere, but how to find where not so easy without some test gear.

I have a DMM , but I'm not sure how to go about

 

[EFLImpudence]

Are you saying the fuse keeps blowing?

 

[abzee]

Are you saying the fuse keeps blowing?

yes

 

[EFLImpudence]

That must be a dead short between a line(live) wire or part and earth somewhere.

 

[EFLImpudence]

So test for continuity between Line(live) and earth at various points.