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 17 replies
  • Subscribers 27 subscribers
  • Views 1150 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

RCBO In Distribution Board or Isolator With RCD?

Nano Brewery
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.

  • 0
    It depends...


    Firstly, which requirement for RCDs are you attempting to satisfy? (in many situations on a TN system they'd likely not be required at all). Are there any upstream RCDs that you'd need to discriminate with (which might suggest against solid N RCBOs for instance).


    Then what are the operational requirements? Is it acceptable to the user to have all the immersions disconnected if one developed a fault? (if they're all part of the same process that might actually be perfectly acceptable or even desirable, in other situations keeping the others running at all costs might be top of the list).


    Are there any earth leakage (protective conductor) currents to take into account? Mineral insulated elements have a bit of a reputation for being a little leaky, and you have quite an amount of them there. On the other hand spread over three phases the leakage should tend to cancel out .... unless there's any option to switch each phase individually (for reduced output for instance).


       - Andy.
  • 0
    Firstly, which requirement for RCDs are you attempting to satisfy? (in many situations on a TN system they'd likely not be required at all). Are there any upstream RCDs that you'd need to discriminate with (which might suggest against solid N RCBOs for instance).



    Cheers Andy.  As I understand it SPNetworks have installed a TNS System.  They have connected via the sub-station down the road.  I have a Earth Terminal Block to connect to - Do this sound right?


    Ther aren't any upstream RCDs at present.
  • 0
    Then what are the operational requirements? Is it acceptable to the user to have all the immersions disconnected if one developed a fault? (if they're all part of the same process that might actually be perfectly acceptable or even desirable, in other situations keeping the others running at all costs might be top of the list).




    I would need the other 3 Immersions to remain connected if 1 develops a fault.


  • 0
    As I understand it SPNetworks have installed a TNS System. They have connected via the sub-station down the road. I have a Earth Terminal Block to connect to - Do this sound right?

    If you're using the supplier's earthing facility it'll certainly be TN. (I'd be surprised if it was really TN-S these days (unless it was an odd situation like a caravan site or a marina) - most DNOs seem pretty wedded to TN-C-S these days, even combining N and PE in modification to what were originally TN-S networks, effectively making them TN-C-S even though they appear for all the world to be TN-S at the cut-out.)

     
    I would need the other 3 Immersions to remain connected if 1 develops a fault.

    Then no common RCD then - which leaves you with a choice of individual RCD (RCCBs or RCBOs) for each circuit, or no RCDs at all - so back to the 1st question on that.


      - Andy.
  • 0
    Are there any earth leakage (protective conductor) currents to take into account? Mineral insulated elements have a bit of a reputation for being a little leaky, and you have quite an amount of them there. On the other hand spread over three phases the leakage should tend to cancel out .... unless there's any option to switch each phase individually (for reduced output for instance).




    Not sure what Protective Conductor means?


    No option to switch each phase, just able to switch individual elements on/off depending on output required, i.e 9kW or 15kW (9kW & 6kW).


    These are the elements I'm looking to install: https://processheatingservices.com/immersion-heaters/screwed-immersion-heaters/industrial-heaters-piirange/


    Cheers, Dan.


  • 0
    If you're using the supplier's earthing facility it'll certainly be TN. (I'd be surprised if it was really TN-S these days (unless it was an odd situation like a caravan site or a marina) - most DNOs seem pretty wedded to TN-C-S these days, even combining N and PE in modification to what were originally TN-S networks, effectively making them TN-C-S even though they appear for all the world to be TN-S at the cut-out.)




    Cheers Andy.  Spot on!  I've just double checked the SPNetwork invoice and it is 40kVA TN-C-S.  It's for a Nano/Micro Brewery.  I'm hoping to do a fair amount of the install myself and get a qualified sparky to connect tails, check and test before operation.


  • 0
     
    I would need the other 3 Immersions to remain connected if 1 develops a fault.

    Then no common RCD then - which leaves you with a choice of individual RCD (RCCBs or RCBOs) for each circuit, or no RCDs at all - so back to the 1st question on that.




    The Control Board is already built, came with the rest of the gear.  It has Rail Mounted Cartridge Fuse Holders.  I think the most economical solution would be to fit downstream Isolators with RCDs?  Would you agree?  Thinking I would like RCDs for the extra safety?  Cheers, Dan.


  • 0
    Not sure what Protective Conductor means?

    The one that's there just for protecting against electric shock - usually coloured green/yellow - in olden days used to be referred to as the "earth" wire.

    I'm hoping to do a fair amount of the install myself and get a qualified sparky to connect tails, check and test before operation.

    There's an old addage that quality (or safety) can't be just tested-in - it has to be designed-in and built-in. And there's more to that than just chucking RCDs at the problem and hoping for the best. It's sounding like an unusual situation with perhaps more liquid and a lot more metalwork than a typical domestic. Industrial systems perhaps tend to rely more on solid earthing and bonding rather than RCDs. Certainly get someone else involved if you don't have all the requisite skills - but I'd get them involved at the start of the process rather than the end - and make sure it's someone who's familiar with that kind of installation - many a domestic electrician who hold all the qualifications for that end of the market might be quite out of their depth with something more unusual.


       - Andy.
  • 0
    As Andy said.

    Get someone who has the required skill, qualifications and experience to design, install, test & inspect. They might well be favourable to you doing a lot of the donkey work under their supervision and therefore you`d save a shilling or two in the process.
  • 0
    Cheers both of you.  I have had two electricians to look and quote.  Both quotes were well out of my budget.  It's only a very small brewery.  I am now getting advice/guidance from another to do most of the work myself.  It's always good to get a 2nd, 3rd or 4th opinion though.

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