Single & Double Module RCBO & 1 or 2 Pole RCBO meaning

Discussion in 'Electricians' Talk' started by hardeep0071, Mar 1, 2011.

  1. hardeep0071

    hardeep0071 New Member

    what is difference between

    Single & Double Module RCBO,    1 or 2 Pole RCBO

    what is pole and module meaning
    (see my consumer unit)
    few year back I installed an outdoor power socket and for safety i wanted to put rcd on it so, if i will buy MK masterseal with rcd (outdoor socket) i think that will be allright by regulation, but i think rcd will mallfuction in cold weather or may stop working prematurely. so i thought that i should put MK masterseal without rcd outdoor and then in consumer unit i will put RCD. but actually rcd is quit wider than than the empty slot i have in Consumer unit so after reading on internet i found RCBO is better than rcd and mcb as it has both so i thought of putting it there as its slim aswell compared to rcd. by the way my house consumer unit haven't got rcd so shall i take out current 32 amps mcb and replace it with same ampere size RCBO.
    shall i remove it and replace it with 32 amps RCD by removing current garage MCB and next to it vaccant MCB.

    i will love to have first idea if its possible as i can use left one MCB in future.

    will it effect if i replace 32 amps MCB with higher current rating RCBO like 40a, 45 or may be 50a (please give reason why not please dont say for example if in 5 amps wall plug i will use 13 amps then that device will burn because i know we have gone higher than device current rating and in the case of fault fuse wont blow but device will burn not good. but RCBO are not like that in the case of fault RCBO will just trip.

    thank you so much


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  2. unphased

    unphased Screwfix Select

    A module is one single device that will occupy one standard width, one way in a fuseboard for example. A single mcb is one module. An example for two modules would be the main switch as it takes up the width of two single modules or two ways. So a single module RCBO will occupy one single way and a 2 module RCBO will occupy two ways in width. A single module would normally be single pole and two modules double pole but not necessarily.

    Pole is a confusing term but I will try to explain it. There is no official definition given in Part 2 of the regs. In my way of thinking a pole refers to a single line of current through a device. So a single pole device will either be phase or neutral, both having only one conductor path through them and are either phase live or neutral live. Generally fuses and switches are referred to as single pole or double pole (similarly mcbs and RCBOs). The regulations only permit single pole switching of a live condutor (never a neutral conductor on its own). Switches are generally single pole for this reason. However, for full isolation both live and neutral need to be broken for safety, so they switch double pole ie both the live and neutral conductor are broken by the switch at the same time. This is double pole live and neutral. Triple pole and quadruple pole will have similar meaning. Triple pole will have three live conductors and quadruple pole four live conductors and so on. I hope that expains it. :)

    To answer your second question matching RCBO or mcb ratings to circuits has nothing to do with polarity or modules. You need to understand circuit design to know what size cable to use and what size fuse or mcb to protect the circuit. It is far more complex than your question suggests.
  3. sinewave

    sinewave Screwfix Select

    Rollin' in the deep!
  4. CraigMcK

    CraigMcK Screwfix Select

    But not all double module devices are double pole ;)

    Double module RCBO's with pig tail N's are usually single pole switching (Line only)
  5. Dale76uk

    Dale76uk Guest

    don't they disconnect the Neutral as well???
  6. sinewave

    sinewave Screwfix Select

    Tis all in the name Dale!

    Double module just means the device in question will fill two bus bar spaces in a CU or DB.

    Double pole means it switches the Line & Neutral conductors.

    A Double Pole device can also be a Single Module, Double Module or even a Quad module device!

    Simpleeeeeeeeeeeess!  :)
  7. unphased

    unphased Screwfix Select

    hardeep. It would help everyone to answer if you posted new questions after replies have been posted rather than editing your original post! Looking at your photo you have an old MK Sentry fuseboard. It would make far more sense to change this to a modern 17th edition compliant fuseboard than try to fit RCBOs to your circuits. Would MK sentry RCBOs fit this board?

    Some terminology confusion is evident in your edited post.

    An RCBO is a device that combines an RCD and mcb in one unit.

    An RCCB is a Residual Current Circuit Breaker, usually double pole (but could be single or triple or quadruple).

    I see a hole appearing with a shovel alongside it.

    Hope this helps. :)
  8. CraigMcK

    CraigMcK Screwfix Select

    Whats a fuse funtion in an RCD?

    RCCB = RCD
  9. hardeep0071

    hardeep0071 New Member

  10. unphased

    unphased Screwfix Select

    Doh. I knew this would happen. Read the post before you reply. I said RCBO has a combined fuse and RCD function. RCD being the overall generic reference (Residual Current Device) whereas RCCB is a Residual Current Circuit Breaker, commonly fitted on dual RCD fuseboards, and is double pole as far as I know. An RCD could rfer to anything which has this function. Okay!
  11. CraigMcK

    CraigMcK Screwfix Select

    you edited your post after it had been questioned, thats something you complained about hardeep doing ;)
  12. unphased

    unphased Screwfix Select

    :). No hardeep edited his post to ask a new question. I edited mine to ...oh..what ever...:)

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