At 240V, the current is 52A and the load is 12.5kW.
Kiln cable size
- Thread starter geraldthehamster
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True - you did make that point before, and I'd forgotten that the 47.7A related to 220V. However, even if most people get about 240V, we're meant to do calculations at 230V, and (provided there are NO other loads) that just scrapes in for a 50A MCB at 49.9A !
Mind you, if it is 10mm² cable, then 25m of that is going to introduce a VD of about 5.5V at ~50A. If the supply is a nominal 230V at the origin of the installation, then the voltage at the kiln will be 224.5 or less, hence the current no more than about 48.7A.
Have said all that, as I and others have said before, 10mm² cable is at best pretty marginal, and I probably wouldn't personally consider using it for such a load.
Kind Regards, John
Are there any derating factors?
10mm² T+E has a maximum CCC, method C, of 63A.
10mm² T+E has a maximum CCC, method C, of 63A.
I think the issue here is more to do with VD rather than CCC.
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It is 5.5V @ 230V, 2.2%.
What's wrong with that?
What's wrong with that?
We haven't discovered that.
It does - which is why I said that it would probably be OK on a 50A MCB 'with most installations methods'.
It's more the MCB that I'm concerned about. As flameport and I have pointed out, a 50A one is clearly very close to the mark (depends on how one does ones sums), and that assumes absolutely no loads other than the kiln (which is probably unlikely). If one had to move to a 63A MCB (if one were available) or, more likely a 60A or 80A fuse in a switch-fuse, 10mm² cable would become even more marginal (or, with any de-rating factors, or an 80A fuse, unacceptable).
Kind Regards, John
Indeed...
Nothing. In fact, as I said, it 'helps' a little by reducing the current drawn by the kiln, making a 50A MCB a little more (just about) acceptable.
Kind Regards, John
Ambient temperature will be significantly above normal at the garage end.
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As people are still interested in discussing this:
The cable travels the length of the bungalow, travelling mostly in the web of two steels that support dormers, and not encased in insulation.
Once emerged in the (uninsulated) garage, the portion of cable not yet installed will travel from the consumer unit there for 4 metres to the back of the garage, and thence:
Into a separate brick built workshop on the back of the garage, in which it travels another 4 metres or so to where the kiln is located. Obviously the ambient temperature in the workshop will rise when the kiln is firing.
The most that would also be running in garage or workshop, while the kiln was firing, would be two fluorescent tubes.
As already stated I will be taking on-site advice from a kiln installer. But I'm interested in the discussion.
Cheers
Richard
Then if the ambient temperature is no greater than 40°C (possibly 42 or 43) then the cable will be suitable.
Yes, probably (I haven't looked up the figures) but it clearly remains very marginal. As for the ambient temperature, even that 'outdoors' can rise into the 30s during a 'heatwave', and is commonly in the mid/high 20s, which wouldn't leave all that much scope for heating by the kiln.
Kind Regards, John
I've never had a kiln but I don't think they are made to heat the room.
I'm sure they aren't - but they get so hot inside, and tend to remain so for quite long periods, that I can but presume that they have an appreciable impact on temperature of the surroundings.
Are they 'vented' to the outdoors in any way?
Kind Regards, John
That was my guess. If that's the case, then all the generated heat has got to end up in the room (workshop/garage), at least until it escapes into the outside world. Think of five 2kW fan heaters running at full blast in the workshop/garage for a few hours!"
Yes, that would solve that particular problem, if it existed (which I suspect it would).
Kind Regards, John
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