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electric shower Interlock

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  • 14-09-2010 5:18pm
    #1
    rockblu
    Closed Accounts Posts: 28 ✭


    Hi im just wondering could anyone give me the correct name of two devices so i can get them in the electrical wholesalers.The set up is an interlock between two electric showers consisting of the following: 40 amp breaker,5 amp breaker,63 amp rcd, there are 2 devices like single phase brakers but no switch on them,each have a pair of wires coming from terminals on the top to a coil which surrounds each supply going out to each shower.what are these devices called?
    Then next to these are two what i think are relays?they have the relay symbol on them and a switch on the front which is either in the on or off position,again what is the correct name for these?
    any info would be greatly appreciated,thanks.


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    #2
    indie armada
    Registered Users Posts: 834 ✭✭✭indie armada


    i think the one with two contactors is the non priority unit.


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    #3
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    rockblu wrote: »
    Hi im just wondering could anyone give me the correct name of two devices so i can get them in the electrical wholesalers.The set up is an interlock between two electric showers consisting of the following: 40 amp breaker,5 amp breaker,63 amp rcd, there are 2 devices like single phase brakers but no switch on them,each have a pair of wires coming from terminals on the top to a coil which surrounds each supply going out to each shower.what are these devices called?
    Then next to these are two what i think are relays?they have the relay symbol on them and a switch on the front which is either in the on or off position,again what is the correct name for these?
    any info would be greatly appreciated,thanks.


    The devises with pairs of wires out of the top to a coil around each supply are current sensors.
    The devices you think are relays are the contactors, contactors are in fact big relays.


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    #4
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    indie armada wrote: »
    i think the one with two contactors is the non priority unit.

    Yes thats right, the one with a single contactor is a priority unit.
    The priority shower is direct connected and has the current sensor around its supply out from interlock, while the secondary is through the contactor which energises when the current sensors detects a load on the priority shower. The normally closed contactor cuts off the secondary shower even if its in use when the priority one is turned on.


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    #5
    indie armada
    Registered Users Posts: 834 ✭✭✭indie armada


    the non priority units seem to be more common, the necessity to be able shut down the secondary shower when the primary is switched on is usually not required and ppl are generally happy with one shower opperating at a given time.


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    #6
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    indie armada wrote: »
    the non priority units seem to be more common, the necessity to be able shut down the secondary shower when the primary is switched on is usually not required and ppl are generally happy with one shower opperating at a given time.


    Yea but a non priority unit is more expensive, a priority one is usually used in cases where its less likely a person using the secondary one would be interrupted by someone switching on the primary one,

    The non priority one is better, its just more expensive. Shutting down the secondary is not done through necessity really, except the load necessity, its just a cheaper option than the better but dearer non priority where the one in operation cant be interrupted.


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    #7
    rockblu
    Closed Accounts Posts: 28 ✭rockblu


    Thanks for the awnsers lads,just to clear it in my own head right, there are two current sensors and two contactors,so which ever shower is powered on first that gains priority how?what creates the interlock?


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    #8
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    rockblu wrote: »
    Thanks for the awnsers lads,just to clear it in my own head right, there are two current sensors and two contactors,so which ever shower is powered on first that gains priority how?what creates the interlock?

    The 2 showers are fed through 2 seperate contactors, the contactors have contacts that are normally closed (n/c) so both showers have 230v up to them when they are not actually running. Shower one goes through its contactor, but its contactor is controlled by the current sensor of shower 2 and vice versa. So when shower 1 is actually set in motion the current it draws is sensed by the current sensor around its power cable which energises the contactor of shower 2, which now opens the contacts of the second contactor so now shower 2 has no power up to it so it cant be started. And the same if shower 2 is started. Once one is going the other cant start. This is a non priority interlock.

    The priority one only has one contactor and is similar in operation except shower 1 can be started but will knock off shower 2 if shower 1 is started even if shower 2 was running, once shower 1 is started shower 2 cant start. Shower 1 is the priority one in this case because it can over-ride shower 2.

    If your thinking of making one up its just easier to buy one, not a lot if any difference in cost, and a lot of hassle saved.


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    #9
    rockblu
    Closed Accounts Posts: 28 ✭rockblu


    on the ball cheers robbie,you have cleared that right up,no longer confused,thanks.


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    #10
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    rockblu wrote: »
    on the ball cheers robbie,you have cleared that right up,no longer confused,thanks.

    It may be done with normally open contacts where the 2 contactors are energised the whole time and the current sensor relay drops out the contactor of the shower not running while the other is, i forget which type they sell in electrical wholesale shops but the principal would be the same. The advantage of normally open ones is if the control MCB on the interlock trips, neither shower will operate so we know something is wrong. So it may well be normally open contactors used, its a while since i installed one of the shower interlock units.

    Update,,,
    Yes its the normally open contactors that are used, so when the interlock unit is setup both contactors are energised and so all contacts are closed, when shower 1 is operating, its current sensing relay causes the contactor of shower 2 to drop out so it cant start, and vice versa when shower 2 is operating. So its exact same as previous post but normally open contactors used and are energised to have the 230v supply to both showers. Hopefully have not confused you again now.

    Both showers can actually be run cold as there is not enough load once the heating elements are off to cut off the other shower.


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