Induced voltage from underfloor heating?

[razorbill]

Following recent building work, I have electric underfloor heating installed under bamboo floor.

Some people with sensitive skin experience a shock when touch an earth point and underfloor heating is heating.

Wiring checked and double checked, definitely not an earth bonding issue. The problem ONLY occurs when touching a "good" earth (and so path to earth).

RCD protected - doesn't trip (RCD is working). Current flow is so low its unmeasurable on my meter.

I can consistently measure small AC (10 - 15V) voltage from floor to earth, across the whole floor (i.e. from any point on the floor to earth).

Solid wood 15mm floor is an insulator (according to Megger).

This appears to be some sort of induced voltage on the floor surface (capacitance / inductance?). Supplier claims they have not seen this problem before.

Has anyone else similar experience? Is such a voltage "normal" for underfloor system? If so, what voltage is expected?

(And I wonder if a previous thread Help Needed - 'Live' walls
//www.diynot.com/forums/viewtopic.php?p=880713#880713
is really another manifestation of the same effect)

 

[pompeygit]

Wonder if it is the condition 'perceived electric shock' as outlined on P65 of EGTTBR. This condition is found in TNCS installs and is caused by impedance of the PEN conductor causing a voltage above true earth. Does the installation have a higher than normal Ze? I would guess it is L to N problem of some sort as RCD does not trip. Other than that I am stumped.