My step-father had to look after a kiln on a regular basis - that one was within a wooden-hut type of room which was also used for teaching classes. Boiling hot applied in all but the very coldest weather.
Yeah, Newton's law of cooling, and stuff. For varying degrees of approximate.
Owain
Don't do much potting in the summer: too much to do in the two gardens I look after! But in the winter the kiln is run overnight on E7, and the door to the room is left open to let the heat circulate around the house. It takes longer to cool down than it does to warm up, at least
12 hours but I usually leave it 24 to make sure the pots inside cool slowly and the glaze doesn't crack, or worse, the pots themselves. It's a bit like a nightstore heater.
The heat transfer per unit area through a given wall is proportional to the difference in temperatures of the two surfaces of the wall. (Improving the composition of the wall by making it thicker and especially adding insulation reduces the heat transfer coefficient.)
It's more complicated when you consider the convection inside and outside the kiln or oven. For example, you normally want to cool some parts of an oven so it doesn't set the cabinets on fire & the electronics don't overheat.
Inside a kiln, heat transfer by convection is only significant below a few hundred °C. Above that, radiation kicks in big time and is the main heat transfer process.
No experiences of kilns, however lots of experiences with ovens... I have 2 x 3Kw ovens - both originally plugged into the kitchen ring via standard 13A plugs.
One was supplied with a moulded 13A plug - after 2 years of 5 days a week use the plug had gotten so hot that it melted the insulation round the live pin and charred/cracked the wall plate.
The other oven had a "heavy duty" (B&Q) plug fitted by me, and it did the same thing.
These ovens are run for a few hours most mornings (home based microbakery) and take an hour or 2 to heat up before the thermostats go into the usual intermittent mode.
They're now both on fused switched outlets...
See:
For the gory details...
So if you are plugging a 3Kw load into a 13A socket that will run for some hours before starting to cycle, then I'd really consider hard-wiring them into fused outlets, or if-not, then make sure the plugs really are high quality, polish the metal bits & fuse and check regularly, and if it ever smells "fishy" or of "dead rats", then you know somethings wrong...
Gordon
it's too dark to read! (sorry)
Good point --- I was thinking mainly of ovens.
Could you use 16 or 32 A "industrial" sockets with appropriate protection?
In article , Gordon Henderson scribeth thus
What about using a 16 amp Commando type outlet or does queens regs say you can't?..
Technically, all outlets in domestic situations must be shuttered.
However, if it were out of reach, or of an interlocked type (cannot withdraw plug without turning off, cannot turn on without inserting plug) that would meet the spirit of the regs.
Therein lies another story:
Many year ago I had the house rewired and shortsightedly specified a 'kiln spur' of 30A going to the little outbuilding where the kiln will be placed. The cabling was put in, but only now, when I come to use it, do I find it 's not actually wired up to the CU!
Robert
A Commando outlet? Does that mean bare unprotected live wires?
Robert
Better still just a DP switch, no fuse. It's the fuse that gets hot and melts things around it. BTDTGTTS with 3kW storeage heaters and brand new, reputable brand, SFCU:
Storeage heaters connected via 2.5 mm^2 flex to the 2.5 mm^2 spur so protection is via the 16A MCB in the CU.
Doesn't the flap on a CEEform oulet count as a "shutter"?
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