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 8 replies
  • Subscribers 32 subscribers
  • Views 1736 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

Compliance with 411.3.3 RCDs on Socket Outlets

An_Cala

I have a scenario where we have a standard circuit arrangement. 32A Ring Circuit feeding a number of socket outlets.  An RCBO of 32A/30mA is specified at the DB.  However the outlets also have 10mA RCD's at each outlet.    Whilst there may be issues around nuisance tripping. ITs been suggested that we remove the RCBO and use a standard 32A Type B MCB at the DB.

 IMO this means the circuit would not have RCD protection,  and only the outlets ( or appliance plugged into an outlet would be protected).  So the question I have is would a 32A MCB Ring circuit when serving this arrangement be compliant with the regs?

One concern I have with this is that should an outlet ever be changed for a normal 13A SSO, then the circuit again would be non compliant.   And that in the event of an earth fault (depending on the ZS) it may not achieve the necessary disconnection times for a ring circuit. 

 

Thoughts? 

Parents
  • 0

    I can not see a reason for removing RCD protection (RCBO in this case) from the circuit. I do not see a problem with having 10mA RCD protection at each individual outlet all on the same circuit.

    The RCBO will protect the circuit and it`s wiring as required in BS7671 and you`ll also have some 10mA non BS7671 protection at each individual outlet. If any outlet is changed for a straight forward outlet then no problem either.

    OK, let`s see what happens in an earth fault with an appliance. You have 10mA RCD (non standard) that would be OK in an ideal world with a non electrically leaky appliance and in theory would be more sensitive than the 30mA RCD. in a fault then both might trip or a very small fault only the 10mA might trip. As stated the socket 10mA inbuilt RCD will almost certainly not comply with BS7671 but may well give you a bit better protection. It could be a nuisance in some instances especially if your appliance has mains filters.

    I would not remove the circuit RCBO but I might change some sockets to non RCD types if they cause problems. Otherwise I`d be inclined to leave them in place.

    PS, you could change the sockets to inbuilt 30mA ones too. 

    If , as stated, your RCD sockets are to BS 7288 then BS7671 says you can not rely upon them a the sole means of RCD protection where needed, it does not state that you can not have them

Reply
  • 0

    I can not see a reason for removing RCD protection (RCBO in this case) from the circuit. I do not see a problem with having 10mA RCD protection at each individual outlet all on the same circuit.

    The RCBO will protect the circuit and it`s wiring as required in BS7671 and you`ll also have some 10mA non BS7671 protection at each individual outlet. If any outlet is changed for a straight forward outlet then no problem either.

    OK, let`s see what happens in an earth fault with an appliance. You have 10mA RCD (non standard) that would be OK in an ideal world with a non electrically leaky appliance and in theory would be more sensitive than the 30mA RCD. in a fault then both might trip or a very small fault only the 10mA might trip. As stated the socket 10mA inbuilt RCD will almost certainly not comply with BS7671 but may well give you a bit better protection. It could be a nuisance in some instances especially if your appliance has mains filters.

    I would not remove the circuit RCBO but I might change some sockets to non RCD types if they cause problems. Otherwise I`d be inclined to leave them in place.

    PS, you could change the sockets to inbuilt 30mA ones too. 

    If , as stated, your RCD sockets are to BS 7288 then BS7671 says you can not rely upon them a the sole means of RCD protection where needed, it does not state that you can not have them

Children
No Data

Community Rules & Guidelines