Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 44 replies
  • Subscribers 26 subscribers
  • Views 2822 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Are RCD's Required?

Nano Brewery
Hi, looking to understand if an RCD would be a required regulation (and/or just highly recommended) in the following situation.  The additional cost of installing four or five 3-Phase RCDs is quite substantial and I would prefer to avoid it if still deemed as safe and not legally required.  Earthing system is TN-C-S.


For connecting up 4x Immersion Elements (9kW, 9kW, 6kW, 3kW) in Brewery Tanks I am looking at either:


A.  SWA Cable clipped direct to basket from the Control Panel to IP rated Plugs/Sockets mounted on the wall.  Then floating SY Cable (recommended by electrician) 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.


B.  Same as above but swapping the Plugs/Sockets for Isolators.


Look forward to your feedback and opinions.  Cheers.
  • 0
    AJJewsbury:
    switched via PID for temperature control

    How does the PID (proportional–integral–derivative) temperature controller vary the power? If it's chopping the a.c. waveform (like a big dimmer) as I understand some do - I'd be very wary of putting RCDs downstream of it.


    Andy, I think that you meant upstream.


  • 0
    Chris Pearson:
    AJJewsbury:
    switched via PID for temperature control

    How does the PID (proportional–integral–derivative) temperature controller vary the power? If it's chopping the a.c. waveform (like a big dimmer) as I understand some do - I'd be very wary of putting RCDs downstream of it.


    Andy, I think that you meant upstream.




    This time I did mean what I wrote ? - there have been suggestions for individal RCDs (RCCBs or RCBOs) for each immersion heater - which would have to go downstream of the controller. I really don't like the idea of feeding an RCD a non-sinusoidal supply (the potential for the residual current being non-sinusoidal is another issue).


       - Andy.


  • 0
    AJJewsbury:
    Chris Pearson:
    AJJewsbury:
    switched via PID for temperature control

    How does the PID (proportional–integral–derivative) temperature controller vary the power? If it's chopping the a.c. waveform (like a big dimmer) as I understand some do - I'd be very wary of putting RCDs downstream of it.


    Andy, I think that you meant upstream.




    This time I did mean what I wrote ? - there have been suggestions for individal RCDs (RCCBs or RCBOs) for each immersion heater - which would have to go downstream of the controller. I really don't like the idea of feeding an RCD a non-sinusoidal supply (the potential for the residual current being non-sinusoidal is another issue).




    I thought that we had reached the conclusion that we just need an RCBO in the DB if at all. However, I interpreted your message as being cautious about the type of RCBO. i.e type AC might not be compatible with the PID, but type A might. AFAIK, TPN RCBOs are type A.


  • 0
    I thought that we had reached the conclusion that we just need an RCBO in the DB if at all.

    I wasn't sure what was intended - both approaches had been suggested at various times (and on various threads). We've got I think a total of 27kW - so at least 40A/phase - as I've not seen any 3-phase RCBOs rated that high yet (usually 32A max) I suspected that an upstream RCBO might not have been intended.

     
    However, I interpreted your message as being cautious about the type of RCBO. i.e type AC might not be compatible with the PID, but type A might. AFAIK, TPN RCBOs are type A.

    That's another issue - it depends on the details - hopefully at worst it's the equivalent of SCRs/Triacs controlling what are in effect three separate single phase loads per channel (hence an A type should suffice as you say) rather than anything that looks like the second half of Fig A53.1 of BS 7671 (which might have implied the need for a B-type).


       - Andy.
  • 0
    AJJewsbury:

    We've got I think a total of 27kW - so at least 40A/phase - as I've not seen any 3-phase RCBOs rated that high yet (usually 32A max) I suspected that an upstream RCBO might not have been intended.


    So can we agree that RCD protection is not required? I must say that I don't see any requirement for it as far as this circuit is concerned.


  • 0
    Higher current ones do exist that would do, (63 amp example) but not in great numbers or variety or indeed from the famous names.

    An RCD incomer and followed by  MCB protection might be easier to source the bits for.

    M.

  • 0
    Higher current ones do exist that would do, (63 amp example) but not in great numbers or variety or indeed from the famous names.

     

    Isn't that an RCCB rather than an RCBO?

    An RCD incomer and followed by  MCB protection might be easier to source the bits for.

    Or just an MCB in the (existing?) board and a separate RCCB afterwards (if RCD protection is indeed needed)

    So can we agree that RCD protection is not required?

    Depends still - there still seems to be a suggestion of plugs & sockets (although strictly speaking the 30mA RCD requirement wouldn't apply to a 63A one feeding everything, although 0.4s disconnection time would). I'm also a bit in two minds about not having seen the situation - I'm imagining a lot of stainless steel, possibly wet concrete floors, large things being possibly being moved about from time to time, certainly large quantities of liquids (both production and cleaning), and operation by non-electrically skilled persons (although I might be confusing it with a winery I visited once).  If so, a bit of additional protection might not go amiss.


    I do wonder if it could be simplified by splitting the heaters into two groups having an extra controller and then feeding each from a simple 32A RCD protected socket (63A sockets looks to be surprisingly (reassuringly?) expensive).


       - Andy.
  • 0
    Isn't that an RCCB rather than an RCBO?

    sorry, yes it is. A serious lapse of concentration there.

    You may have to use an MCB with the option of a shunt trip and auxiliary current transformer to get that functionality then. Realistically it is not cost effective, and separate MCB and RCD are the way to go.
  • Former Community Member
    0 Former Community Member
    Weirdbeard:

    Hi nano were there any installation instructions with the panel? A link would help :)


     


    Hi nano, any update on this? 


  • Former Community Member
    0 Former Community Member
    Then floating SY Cable (recommended by electrician) from the wall to the Tanks, which is about a 2m run. 


     

    nobody commented on the use of SY, Wouldn't HO7 be the right cable to use here?

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines