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ESB night storage circuit

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  • 15-04-2012 11:09am
    #1
    funcrusher
    Registered Users Posts: 9 ✭


    I'm trying to figure out the circuit protection on a newly connected installation. 16kVA supply with a 100A fuse, linked to an incoming 24hr meter and also a dedicated Night Storage tariff circuit. NS controlled by a separate ISKRA meter type 07MID003 and an ISKRA contactor NSH100. Both these devices are marked 100Amp rated. Both incoming circuits feed through customer disconnect switches to respective consumer units All standard stuff....

    BUT is there any circuit protection within the contactor to limit the NS load? As NS involves huge constant loads, what prevents the combined night-time load of both circuits exceeding the 100A ESB fuse? Some ESB literature makes a casual reference to a limit of 12kVA on NS supply, but I see no sign of any circuit protection - so maybe that is merely guidance to installers.

    I imagine that ESB use design precautions which assume their fuse may not fail below say 120A, and that their supply cable must be designed to safely carry in excess of 120A. But we don't want to blow the ESB fuse.....

    I can easily design and install more protection if necessary - but is it already built-in into the ESB apparatus?


Comments

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    #2
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    esbn dont combine the loads for service and fuse size
    -diversity basically

    there is in theory a risk of the combined loads causing a problem


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    #3
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    with the 16kva supply and separate nsh meter

    the code of practice probably specifies the amount of storage heating ,prob 13 or 16kw

    as long as the storage heating doesn't exceed the quota and the 16kva supply is suitable for the installation(demand,showers interlocked etc.), and the tails and main ocpd's are sized correctly there should be no problem

    it is different to dual - tarriff in respect of discrimination of consumer's main ocpd and cut-out fuse alright


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    #4
    funcrusher
    Registered Users Posts: 9 ✭funcrusher


    Thanks for these comments. They seem to confirm my suspicions. I also suspect that the effect of exceeding 80Amp demand on a 16kVA supply is that you suffer a larg voltage drop due to the length of the supply cable from the ESB transformer (about 150m in this case). I guess ESB have design criteria on voltage drops which are probably the limiting factor. Since poer of notors depends on Volts squared, a 10% drop in voltage means a 19% drop in power.


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    #5
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    funcrusher wrote: »
    Thanks for these comments. They seem to confirm my suspicions. I also suspect that the effect of exceeding 80Amp demand on a 16kVA supply is that you suffer a larg voltage drop due to the length of the supply cable from the ESB transformer (about 150m in this case). I guess ESB have design criteria on voltage drops which are probably the limiting factor. Since poer of notors depends on Volts squared, a 10% drop in voltage means a 19% drop in power.

    not really
    the voltage drop isn't meant to act as a brake


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