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7,300 Watts supplied on a 2.5mm2 T&E.

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Yes a 2.5mm2 T&E cable can supply a 7,300 Watt instantaneous water heater at 240 Volts. I came across this today. The supply was from a B32 M.C.B. So why do we use bigger cable than 2.5mm2 if it will do the job?

The run was about 5m maximum. 

Z.

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    very very roughly, with ambient temp 30 degrees, with a 32 A load after a few minutes use (up to 5 mins but may be less):

    • Ref method C (clipped direct) get to about 80 deg C
    • Ref method 102# gets to about 90 deg C
    • Ref method 103# gets to well over 100 degrees C

    What's the assumed initial conductor temperature?

    GN 6 (at least my ancient copy) suggests 15min for 2.5mm2 when considering 'duration of load current for equivalent constant load' - suggesting to me at least that a cable would take around that long to get to 70 degrees from cold (ambient) - so I'd expected significantly longer again to 80/90/100 degrees from cold.

       - Andy.

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  • 0

    very very roughly, with ambient temp 30 degrees, with a 32 A load after a few minutes use (up to 5 mins but may be less):

    • Ref method C (clipped direct) get to about 80 deg C
    • Ref method 102# gets to about 90 deg C
    • Ref method 103# gets to well over 100 degrees C

    What's the assumed initial conductor temperature?

    GN 6 (at least my ancient copy) suggests 15min for 2.5mm2 when considering 'duration of load current for equivalent constant load' - suggesting to me at least that a cable would take around that long to get to 70 degrees from cold (ambient) - so I'd expected significantly longer again to 80/90/100 degrees from cold.

       - Andy.

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