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RCBO In Distribution Board or Isolator With RCD?

I'm trying to decide which would be the most suitable and sensible option? 


I have a Control Board that will be switching 4x 3-Phase Immersion Elements.

9kW

9kW

6kW

3kW


Control Board has Rail Mount Fuse Holders & Contactors installed for each circuit.


My question is would it be better to have a suitably rated RCBO installed in the Distribution Board which will be feeding the Control Board or should I go with downstream Isolators with RCD's?  I'm leaning towards the later as I would have separate RCD protection on each circuit.


Look forward to your feedback.  Cheers, Dan.

  • Andy - Would you personally not bother with RCDs? Cheers.
  • Nano Brewery:

    Andy - Would you personally not bother with RCDs? Cheers.


    Depends on the circumstances, of course. If everything is hard wired (not via plugs & sockets), indoors, cables aren't hidden in walls and nothing goes near a bathroom or other special location, the earthing system is TN, and everything was to a good standard, then they wouldn't have been my first thought. Seeing the setup might change my mind though...

       -  Andy.


  • Cheers Andy.  I was thinking of going with SWA Cable clipped direct to basket from the Control Panel to IP rated Plugs/Sockets mounted on the wall.  Then floating SY Cable (been recommended) from the wall to the Tanks, which is about a 2m run.  Thinking Plugs/Sockets just to make life easy if I ever want to move things around and also for easier access for cleaning.  Could just go with hard wired Isolator though if this would negate need for RCD?  Earthing system is TN-C-S.
  • Nano Brewery:

    Cheers Andy.  I was thinking of going with SWA Cable clipped direct to basket from the Control Panel to IP rated Plugs/Sockets mounted on the wall.  Then floating SY Cable (been recommended) from the wall to the Tanks, which is about a 2m run.  Thinking Plugs/Sockets just to make life easy if I ever want to move things around and also for easier access for cleaning.  Could just go with hard wired Isolator though if this would negate need for RCD?  Earthing system is TN-C-S. 




    Any more thoughts on this Andy?...


    Wondering if an Enclosure with RCD could be an option for individual protection?... https://www.cef.co.uk/catalogue/products/1051602-3-module-insulated-ip65-enclosure


    Also wondering if a direct feed from a Distribution Board RCD to the Control Panel could be an option for universal protection at less cost?  Is this possible and allowed?


    Thanks for your feedback.


  • What does this control panel do? If there are any electronics in there then that might have an implication for RCDs - especially if it might try to regulate things by chopping the AC waveform to the heaters.


    Will all the elements be on the same item of equipment? (I'm just wondering if it makes more sense to mount the control panel along with the heaters on the (movable) equipment and then have a single lead to a wall socket (which would presumably then be rather a large one >>32A and so perhaps not be subject to the 30mA RCD requirement).


    What do the control panel manufacturer's installation instructions say?


    If there are unknowns my gut feeling would be for a single RCD upstream of the controller, with some means to isolate individual elements so that if one goes faulty it can be isolated and the RCD reset to allow the others to continue to to work - but as before there are lots of factors many of which I can't see from here so don't take that as a recommendation.


       - Andy.
  • AJJewsbury:

    What does this control panel do? If there are any electronics in there then that might have an implication for RCDs - especially if it might try to regulate things by chopping the AC waveform to the heaters.


    Will all the elements be on the same item of equipment? (I'm just wondering if it makes more sense to mount the control panel along with the heaters on the (movable) equipment and then have a single lead to a wall socket (which would presumably then be rather a large one >>32A and so perhaps not be subject to the 30mA RCD requirement).


    What do the control panel manufacturer's installation instructions say?


    If there are unknowns my gut feeling would be for a single RCD upstream of the controller, with some means to isolate individual elements so that if one goes faulty it can be isolated and the RCD reset to allow the others to continue to to work - but as before there are lots of factors many of which I can't see from here so don't take that as a recommendation.


       - Andy.




    Cheers Andy. 


    To clarify the Control Panel has 6 Three-phase circuits.  Each circuit has Rail Mounted Cartridge Fuses, Contactors, On/Off Rotary Switches and Pilot Lights.  At present I will only be using 4 of these circuits to switch each of the immersion elements when required.  2 of the 4 circuits being used will be switched via PID for temperature control.  It does not have any RCD protection.


    2 elements on one vessel, 2 elements on another.  Vessels are about 3m apart.  Interesting idea though.


    Don't have any Control Panel instructions.


    When you say "upstream", do you mean before the Control Panel?  Wondering if a direct feed from a Distribution Board RCD to the Control Panel could be an option for universal protection at less cost?  Is this possible and allowed?  Alternatively, tails split with a Henley Box >>> RCD >>> Control Panel?


  • When you say "upstream", do you mean before the Control Panel?

    Yes - analogy with water flow (under gravity)- upstream = closer to the supply, downstream = closer to the load.

       - Andy.