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Double Insulated, yet....

AncientMariner
A few years ago I fitted a Cistermiser in the mens toilets of our village hall. For fitting simplicity I chose the 4 x AA battery option for power, although they do have an inbuilt 240v ac psu.  Today, intending to change the batteries, found that due battery leakage, one of the battery contact strips had corroded away.


Currently my intention is to fashion a new contact strip and thus repair it, but using the inbuilt 240v option also occurred to me.


So why, when this device is double insulated, have the instruction that if pipe minted, then can only be powered by batteries, but if I split the unit and have a cable from the unit to the water valve, I can use either 4 x AA batteries or 240v ac?  As it says on page 10 of https://www.cistermiser.co.uk/wp-content/uploads/2019/01/Infrared-Control-Valve-IRC%C2%AE-Installation-Guide.pdf  in Section 5.Power  "Do not mount a valve with Mains power directly onto pipework." "When fitted directly onto pipework, only use Battery power."


Seems strange.


Clive






  • 0
    Oddly we have a similar model at the scout HQ, though supposedly battery only,  and the batteries had failed, and I added an external PSU.

    I suspect the issue here is one of EMC or other CE  approval, the devices having not been tested and approved for use in all possible configurations.

    In leaded mode, is there a ferrite bead on the wire by chance ?


    In practice it may not quite meet the specs, but as a one off, is most unlikely to be dangerous.
  • 0

    So why, when this device is double insulated, have the instruction that if pipe minted, then can only be powered by batteries, but if I split the unit and have a cable from the unit to the water valve, I can use either 4 x AA batteries or 240v ac? 



    Or another possibility - looking at the pictures in the linked manual - it might be double insulated from the point of view of things outside of the enclosure (the usual point of view when considering electric shock), but not double insulated as far as a copper pipe & metal valve body passing through the middle of the enclosure is concerned - i.e. there might only be the equivalent of single insulation between the PCB and pipe/valve inside the enclosure, the enclosure itself providing the 2nd layer of insulation (when no valve/pipe is present).


      - Andy.
  • Former Community Member
    0 Former Community Member
    The limitation re not allowing mains powering if it is pipe mounted may be more about the 230V terminals being in very close proximity to potentially wet pipework, e.g. condensation, drips from the compression joints etc.  It looks like the top-down cable feed and clamping arrangement could funnel any water towards the terminals.  So a possible safety risk for a lazy plumber who might not have bothered to isolate before working on the valve.
  • 0
    The model I had fitted was the old square version, whereas the pdf I linked to is more rounded.

    Anyway, I telephoned their Tech Support line and turns out that the requirement is on the basis that electricity and water do not mix.


    The new model certainly appears more susceptible to water ingress, but the old square version less so, I think. In reply to Brian, to get to the valve for anything more serious than setting the trickle flow, you have to remove the "box" from the solenoid.  The rear of the "box" having a standard 3-pin solenoid valve connector.


    If there is a live loop-in terminal at the nearby ceiling rose, I can go for the split installation method, with the additional, if I can fish through the low voltage cable to the valve...

    Clive

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