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 5 replies
  • Subscribers 32 subscribers
  • Views 549 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

RCD arrangement for garden workshop

JDW
I would like to supply a small workshop/shed with power, which is approximately 5m from my house. The house is a TN-S system

I’ve had a couple of electricians suggest several different ways

They all seem to have different ideas where the RCD should be?

 
  • RCD in main property

  • RCD in workshop (no RCD on SWA to workshop)

  • Two RCDs main property & workshop


Which would be the preferred method?
  • 0
    The preferred method in your particular instance would depend upon 1/ Safety and 2/ inconvenience & cost.


    If, as you say it is a TN-S system then no need for an RCD in the workshop if you are feeding it in SWA cable.

    You will need a RCD (30mA) somewhere and that be via RCCB or RCBOs in the workshop.

    If you feel you need to mitigate, to some degree, Possible RCD failure, you might decide put one RCD in the house and one in the workshop (if they are both standard 30mA non delayed then either one or both might trip during a fault). Plunging the shed say into darkness whilst you go to the house to reset might be a pain to do and it might have safety issues (do you have an emergency light in the workshop).

    You might decide to have a 100mA Time delayed RCD in the house and (double pole switching) 30mA RCD in the workshop - note the 100mA TD RCD does not count as personal protection. 

    If the workshop is for you and only you that might give you a different answer than if it is to protect others (employees too)
  • 0
    ebee:

    The preferred method in your particular instance would depend upon 1/ Safety and 2/ inconvenience & cost.


    If, as you say it is a TN-S system then no need for an RCD in the workshop if you are feeding it in SWA cable.

    You will need a RCD (30mA) somewhere and that be via RCCB or RCBOs in the workshop.

    If you feel you need to mitigate, to some degree, Possible RCD failure, you might decide put one RCD in the house and one in the workshop (if they are both standard 30mA non delayed then either one or both might trip during a fault). Plunging the shed say into darkness whilst you go to the house to reset might be a pain to do and it might have safety issues (do you have an emergency light in the workshop).

    You might decide to have a 100mA Time delayed RCD in the house and (double pole switching) 30mA RCD in the workshop - note the 100mA TD RCD does not count as personal protection. 

    If the workshop is for you and only you that might give you a different answer than if it is to protect others (employees too)


    I like the idea of having the RCD in the workshop, not in the property. but one electrician said that the SWA supplying the workshop must be protected with an RCD


    The other said a fused switch in the main property was fine with the RCD in the workshop 


    The workshop is for private use only, but I do want it to be safe ?


  • 0
    That is simple then. The SWA does not require RCD protection, the best thing is a "Garage" consumer unit in the shed, with an RCD and circuits for lighting and power. It is safe!



    This is not to JDW but the forum.

    Question: Why have the various "electricians" given differing answers?

    SWA needs RCD protection, Oh yes, which regulation says that?

    2 RCDs ditto.

    The answer which best suits the OP is as I said and is capable of being fully compliant. Whether the shed should be TT or not has not come up, Any other comments or reasons for divergence of ideas?



    .Regards

    David
  • 0
    Well unless the sparks cannot terminate SWA. armour correctly, or the Zs is very high at the board so a pick axe would not blow a fuse, all that is needed is some gross

    over current protection for the SWA and for the armour to be earthed at origin.


    Then order of ascending cost at the shed end some options.

    An RCD and a fused spur for the lights,  Note that lights and power trip together for both overload and earth faults

    or  RCD and 2 MCBs, one for lights one for power for two circuits. Note that in this set up lights and power trip together for earth faults, but not overloads

    or an ordinary switch and  two RCBOs if you would like separated lights that stay on with a power fault, earth or overload.


    Some electrical contractors  have not progressed beyond a catalogue of standard solutions.

    M.


  • 0
    Excellent, thank you for your advice?
    I will go for a Garage type CU with RCD Relaxed

Community Rules & Guidelines