Thanks Scott123, for helping me out here.
Crosbie, if you have 3" of kiln stones on all sides, with those elements, it will take quite a few hours for the oven to reach a suitable temp for pizza. Very thick stones act like sponges. They will slowly draw away any heat you put into them. Unless you want to be pre-heating for hours on end, you only want a ceramic hearth, with all other sides being aluminized steel.
Yes, it's possible it could take two hours (or more?
), but if the only place that heat can go is back in to the pizza that's put on it, or into the cold air that enters when the door opens, then that seems very useful latent heat (given one only has domestic 3kW rather than commercial 30kW to play with). And I have a hunch that it's preferable to do 'something else' for a couple of hours while the oven warms up at 3kW than install a 3 phase 30kW supply in order to have a 10 minute pre-heat time and the luxury of an oven with relatively thin metal walls (and a big heat extractor vent above).
The radiant element, imo, is worthless for a deck oven of your size. Both elements need to run the entire dimension of the oven. If your interior space is, say, 430mm by 430mm, you need an element that fills that space. That's how the P049s are set up.
I can see that one might wish to put the pizza under the 43x43cm element if in the rear of a space of 65x43cm. I figure the heat that goes into the 'wasted' stones around the 22x43cm unused space near the oven door will serve as a buffer zone between the hot end of the oven and the end cooled by the door opening.
If you have any hope in pulling this off, I highly suggest mimicking the P049- to an extent. Steel walls and ceiling, space for one pizza, one deck, a broiler element that runs the entire interior dimension and a baking element of the same size beneath the stone. The only changes I would make would be to decrease the vertical height (better top browning with a weak element) and go with a thicker stone.
If the objective was to mimick a commercial oven then I think it would be best to simply buy one, e.g. a PO49.
I'm thinking that in exchange for longer pre-heat, I can use a 1.5kW element to heat a far better insulated chamber with 3" all round of latent heat.
As to decreasing the vertical height, when you remove the element's 2-3cm from a chamber of 11.4cm to leave about 9cm then this is pretty low headroom (you start having to worry about calzone catching on the element).
I'm intrigued as to how different a pizza would come out if either in a 400C oven with top element ON continuously or in a 500C oven with top element OFF continuously (given 3" thick kiln stones all round with 400/500C surface temp @ 120min pre-heat).
I don't know the exact thickness of the P049 stone, but it's par for the course for these ovens to use woefully thin stones.
Commercial users can no doubt spare the electricity to compensate for thin stones from their profits on sales.
You might be able to get away with 19mm thick kiln shelves, but I would go with 25 mm just to be safe. It's better to have to pre-heat for a bit longer than to have a stone that can't cook more than one pizza.
Sure.
The P049 burners aren't bad, but I'd still like to see something squarer with the coil filling the whole square. For instance, if you look at this element here:
http://www.ebay.com/itm/EL93-LINCAT-PO49-PIZZA-OVEN-HEATING-ELEMENT-240V-2KW-/140591304477?pt=UK_BOI_Restaurant_RL&hash=item20bbe50f1d
you'll see it quotes a dimension of 495mm width x 434mm length (inc terminals), but in reality, you can only bake a pizza under the coiled area, so the actual working size is in the vicinity of 495 x 330. You want a square working area to accommodate one single round pizza- ideally, a square element in the 410 x 410 realm and an oven that's only a few mm larger- maybe 420 x 420. 2.9kW doesn't have a hope in heck of pumping out enough heat for a single 614x458mm deck. You need to think smaller, much smaller.
I've actually already availed myself of a couple of those EL93 elements from that very vendor.
They are unsurprisingly a tad flexible - enough to squeeze into the 61x46x11cm deck I plan to build (dual).
The loops are about 42cm peak to peak.
For a metal cabinet I would completely agree that 1.5kW would be insufficient for one deck. However, given extremely low heat loss (a temperature gradient from interior to exterior of 500C to ~40C) then I reckon the 1.5kW should be ample to reach 500C - and hopefully just enough to recover after door opens and 1 or 2 pizza enter.
Edit2: At the end of the day, when you start looking at how much you're going to invest in this project, a project that may not even give you the results you're looking for, isn't the prospect of buying a real oven for your kitchen at least a little bit enticing? If you've got a butane gas kitchen oven that can only bake a pizza in 18 minutes, it has to be anemic enough to be failing you for other foods as well. That oven has to be driving you a little crazy, correct? A generic electric home oven that can hit 287 C. can't be that expensive, even in France- you end up with a real oven that will work for other foods, and there's zero risk. You buy the oven and it will make great pizza.
I was going to simply buy a Lincat PO49x, but then the "Because it's there!" mentality hit me. I figured that perhaps the commercial ovens are optimised for high throughput rather than thermal efficiency, and I could make a different trade off, i.e. longer warm-up + better thermal efficiency for low throughput.
But yeah, I hate the gas oven I have to put up with, but having adjusted the cooking times accordingly I can just about end up with pizza that remains pleasurable to eat. The local professional pizza tends to have soggy bases and is primarily cheese puddles with your choice of meat/veg underneath.
Some brits around here consequently take the wood burning oven route, but that's a much bigger step for the few afficionadoes I reckon than getting an outdoor electric oven that takes 1-2 hours to warm up with zero maintenance.
