Switches near hobs
- Thread starter DavidA1982
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One kW load on 10 metres of cable
Required Cable Size 1 mm
Voltage Drop 1.91 Volts.
Percentage Drop 0.83%
Current Load 4.35 Amps
Max Cable Load* 13.0 Amps
Indeed.
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I understand the current carrying capacity of 1mm cable, but I was under the impression using it on anything other than lighting was not allowed. I've never seen it on an immersion heater for instance even though in theory it can carry the current.
Don't see how it can not be allowed, as long as it complies with the usual stuff for Ib ≤ In ≤ Iz etc.
As you know from many previous discussions, although it is badly written (in particular, "power circuits" is not defined), it would seem pretty clear that the intention of Table 52.3 was that 1mm² cable cannot be used for anything other than lighting circuits, whether it has adequate CCC for the circuit or not.
Kind Regards, John
No, not really - hence the question mark. I'm not really sure, but it just seemed a bit odd to me that an induction hob (which I thought was energy efficient) consumes more power than a double oven. It was a throwaway comment really, I'm not suggesting that Siemens put the wrong info on their hobs or anything.
You are confusing the maximum current needed for each device (6.8kW for the hob versus possibly around half that for the oven. These are measurements of maximum power required at a particular instant.
To make a comparison of energy efficiency, you should look at the consumption over a period of time for each device. This is quoted in KWh (kilowatt hours).
Heating something up on an induction hob would take a fraction of the time to heat the same thing up in a convection oven, so the induction hob is very much more energy efficient.
As I think I said before, the theoretical maximum energy demand of almost any electric hob will be greater than that of an oven, even many/most double ones. Induction hobs generally have even higher maximum energy consumption than traditional ones - but, as I said, 'energy saving' can result from greater efficiency (using maximum energy for less of the time).
Edit: That looks more-or-less like 'snap'
Kind Regards, John
Hobs are very different to ovens.
FYI - a typical 5-burner gas hob on a typical range cooker consumes 15-16kW.
Thanks all - my misconceptions regarding the power consumption of cookers and hobs have been well and truly smashed!
Does anybody have any thoughts on the issue of the cables lying on the floor under the units? Is it acceptable to leave them like this, and if not, can I clip them to the underside of the kitchen units, given that they are already installed and clipping the cables to the wall will be a nightmare?
Does anybody have any thoughts on the issue of the cables lying on the floor under the units? Is it acceptable to leave them like this, and if not, can I clip them to the underside of the kitchen units, given that they are already installed and clipping the cables to the wall will be a nightmare?
The thing to remember is that the figures you're seeing are theoretical maximum ones. Unless there are fancy control systems (to limit maximum consumption) that relates to the situation in which all the elements are 'powered up' simultaneously. In normal use, the elements will cycle on and off all the time (even if all are being used simultaneously, which will often/usually not be the case), so that the average power consumption will be much less than that theoretical maximum, increasingly so as the appliance becomes 'more efficient'. Hence, hypothetically, a very efficient "10kW" hob may well use less energy (for the same tasks) as a much less efficient "5kW" one.
To take a crude and imperfect analogy ... a fancy car may, when run 'flat out' have a maximum speed of 150mph and a certain fuel consumption in that situation. However, in normal usage, the fuel consumption would be much less than that figure.
The pragmatic and the official/'best practice' answers to that will probably differ - so opinions/advice will probably differ as well! The important thing is obviously that the cables be 'safe' from any possible mechanical/thermal damage etc.
Kind Regards, John
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In the good old days, we used to calculate at college the minimum cable size required for a given IH circuit. In theory, we could have used 1 milli.
None of us ever did, but we could. Today though, I'm sure the regs stipulate a minimum of 1.5 for power circuits.
Indeed they do - but, as BAS often points out, Table 52.3 is rather flawed by not defining a 'power circuit'.
For example, we were recently told about a 'dedicated' (OP didn't know why!) circuit for an extractor fan which had been wired in 1mm² cable. In as much as such fans are usually run off lighting circuits, that sounds fine - but it's not really a 'lighting circuit', and the only real alternative is a 'power circuit', in which case it would be non-compliant. Even more interesting (since it's such a ubiquitous situation) is a circuit which supply fan(s) (or shaver sockets etc.) as well as lighting. Is it still a 'lighting circuit'? - if not, an awful lot of 1mm² lighting circuits (which also power fans/shaver sockets/whatever) would be non-compliant!
Kind Regards, John
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