ufo550
Distinguished Member
Thats a good example to give. However, the length of the cable or its resistance is important, but the temperature it is being used at, is equally important. As these two factors alter the volt drop at the end of the cable.
As a water heater is a fixed resistance only, it will still operate at a reduced voltage (i.e. < 5% x 230V). If the voltage is reduced, then so is the current. As the temperature of a cable increases when a load is applied, then its resistance increases, which further affects the volt drop, which further effects the current. I've tried to do some calculations, using a 50m cable reel of 1.5mm flex. Two x 2300w water heaters attached to said reel, would still draw enough current to blow a 13A fuse. But I have no reason to doubt your recollections.
Temperature under loads are an important factor in cable designs, such as cable reels. Manufactures will stipulate the maximum loads for their cable reels, typically 3000w unwound & 1500w coiled (50m). The coiled load is limited as the cable is unable to dissipate the heat generated enough to operate safely, as demonstrated by your picture. Perhaps this cable reel, did not have the thermal safety device fitted.
As a water heater is a fixed resistance only, it will still operate at a reduced voltage (i.e. < 5% x 230V). If the voltage is reduced, then so is the current. As the temperature of a cable increases when a load is applied, then its resistance increases, which further affects the volt drop, which further effects the current. I've tried to do some calculations, using a 50m cable reel of 1.5mm flex. Two x 2300w water heaters attached to said reel, would still draw enough current to blow a 13A fuse. But I have no reason to doubt your recollections.
Temperature under loads are an important factor in cable designs, such as cable reels. Manufactures will stipulate the maximum loads for their cable reels, typically 3000w unwound & 1500w coiled (50m). The coiled load is limited as the cable is unable to dissipate the heat generated enough to operate safely, as demonstrated by your picture. Perhaps this cable reel, did not have the thermal safety device fitted.