G
GEOFF S
Hi
1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.
Cheers
1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.
Cheers
Discuss Immersion Heater in 1.5mm flex in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
Hi
1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.
Cheers
Hi
1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.
Cheers
Which most are,why's that then.?Hi
1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.
Cheers
Which reg relates to 'pushing it'?
Hi
No reg relates to pushing it, i personally dont like running cables near to their maximum, some heat resistant cables have a ccc less than 16 amps some more, also i like to derate due to ambient temp. So 2.5mm runs cooler, less volt drop, better thermal constaints etc. I never said 1.5mm couldnt be used, it depends upon the cable and other factors.
You all have your preferences and veiws, some a little emphatic, i have mine.
Cheers
The tabulated values in the regs book are not the maximum for the cables, they are already worked out to avoid running the cables at their maximum!
All you do by applying the 'I don't like running near the max' approach is to end up wasting money.
Plus the ratings are already at 30degrees so to apply a factor for normal room temperature in this country would actually increase the ccc.
Plus of course the terminals on an immersion heater and cable grip are designed for 1.5 so using bigger cable often leads to broken cable clamps and poor terminations
Looking at table 4F3A, which states current-carrying capacity (no mention of minimum or maximum). I note the current carrying capacity of flexible cables (single phase & non armoured) for 1.5mm & 2.5mm to be 16amp & 25amp respectively. The table does not submit an ambient temperature for those particular figures. However, does start to give rating factors for ambient temperatures from 35'c.Hi
Which tabulated values are they dave? i think you will find they are max values, reference a table please.
Well Dave the life span of a cable reduces the higher the temp, waste money, i dont think so, i bet the I2R losses would easily pay for the bigger cable.
Those little cupboards get toasty with a big copper radiator an ambient temp of 35 C is prudent dont you think?
Your clearly using inferior elements, go for quality.
Cheers
Looking at table 4F3A, which states current-carrying capacity (no mention of minimum or maximum). I note the current carrying capacity of flexible cables (single phase & non armoured) for 1.5mm & 2.5mm to be 16amp & 25amp respectively. The table does not submit an ambient temperature for those particular figures. However, does start to give rating factors for ambient temperatures from 35'c.
It also provides rating factors for 110'c, 150'c flexible cables, 35-80'c x 1 & 35-120'c x 1 respectively, i.e. no effect on current carrying capacities for those cables at those temperature ranges.
If we are to assume the ambient temperature of an immersion heater cupboard to be 40'c (i'e just measured mine at 33'c), a rating factor of 0.82 would apply.
Therefore, a standard flexible cable of 1.5mm & 2.5mm, would have capacity of 13.12a & 20.5a. Heat resistant flexible cables would not have their capacities, affected by this particular ambient temperature.
I see that some heat resistance flexes are sold as heat resistance to 85-90'c range.
My observations are; standard flexible cables would be at or above their limit, in terms of their current carrying capacities in the above scenario, whereas heat resistance would not. To use 2.5mm heat resistance flex for 3kw immersion heater, is not necessary whereas 1.5mm is more than sufficient.
Reply to Immersion Heater in 1.5mm flex in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
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