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LED Lighting Columns Inrush Current

Eddie Currents
I am looking at installing around 21 LED Lighting Columns to a Car Park. It states on the product data sheets that the Lamp Heads are 890mA / 68watts each (I think the 890mA refers to the output current of the driver and not the input current which will be nominally P/V excluding the efficiency of the driver). I have checked all the volt drops and cable calcs which have calculated out at 6mm 3core SWA buried underground. I am splitting the Lighting columns up into circuits and I would prefer to have 7 columns on each circuit. From the information provided on the data sheet it states that the inrush current is 57Amps per column which does seem a little high considering such a small load. This would mean when I select a suitable Overcurrent Device from BS7671 Time Current Curve Charts to withstand the 57Amps x 7 Columns = 399Amps inrush current. Full Load Current being 68Watts x 7 = 476Watts equates to around 2Amps. As 57Amps inrush is quoted (sum of + 399Amps) for the one Lighting Column then the following is concluded:

Assuming a 10Amp Type B – this would be not suitable as this device can only withstand 50Amps up to 5 Seconds so it will cause an instantaneous trip (this would normally be the device i would choose as default)
Assuming a 10Amp Type C – Suitable for a max of 1 Lighting Column as this device can only withstand 100Amps up to 5 Seconds so it will cause an instantaneous trip with 2 Lighting Columns wired on the one circuit
Assuming a 10Amp Type D -  Suitable but only for a max of 3 Lighting Columns as this device can only withstand 200Amps up to 0.4 Seconds and withstand up to 100Amps over 5 Seconds so it will instantaneously trip with more than 3 Lighting Columns wired on the one circuit (i would usually use Type D only on motor circuits and not the usual device of choice for protecting Lighting Circuits)

Deduced from the data sheet and if all is correct, we could only wire a maximum of 3no Lighting Columns per circuit but this using a Type D Overcurrent Device to be sure no tripping will occur during initial spike. This has confused me slightly because I have never seen such high inrush currents like this for such small LED Lighting Loads.

I wondered if any Electrical Designers/Electricians had queried this before with manufacturers and also whether i am missing something. One would expect you could have 7 Columns per circuit as such a small load of 2Amps but the inrush would surely take out the protective device ?   

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    Thanks all that`s great info. Presumably you mean to protect with a 6A fuse not "63A fuse" ? Anyhow I have done exactly that albeit using 6Amp single phase circuits now feeding a max of 3no columns per circuit. They are fairly long runs in different directions so this keeps VD to a minimum too and easier all round. Not keen on the idea of running 3 phase looping in at the metal lighting columns particularly in public places tbh - just my preference and avoids any 400v potential if a fault occurs at a column then the risk is reduced with 230v as a pose to 400v. All Column circuits will go back to a mains enclosure, it`s TT 400A. There are also 20EVC`s hence the reason for the large incoming supply. Main switch is a 400A 300mA (damn expensive but satisfies TT requirement) with earth spike or condudisc at the origin. Trying to work out whether we go earth spike or condudisc but had no experience of using condudiscs so may play safe with spike.
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  • 0
    Thanks all that`s great info. Presumably you mean to protect with a 6A fuse not "63A fuse" ? Anyhow I have done exactly that albeit using 6Amp single phase circuits now feeding a max of 3no columns per circuit. They are fairly long runs in different directions so this keeps VD to a minimum too and easier all round. Not keen on the idea of running 3 phase looping in at the metal lighting columns particularly in public places tbh - just my preference and avoids any 400v potential if a fault occurs at a column then the risk is reduced with 230v as a pose to 400v. All Column circuits will go back to a mains enclosure, it`s TT 400A. There are also 20EVC`s hence the reason for the large incoming supply. Main switch is a 400A 300mA (damn expensive but satisfies TT requirement) with earth spike or condudisc at the origin. Trying to work out whether we go earth spike or condudisc but had no experience of using condudiscs so may play safe with spike.
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