The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Clarifiying matters about ovens

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ivrib's picture
ivrib

Clarifiying matters about ovens

Hello I just joined this wonderful site a couple of weeks ago and keep on making new discoveries all the time. Thanks for sharing all your experiences.

I'm interested in buying a small scale commercial oven and want to understand how different ovens work. I understand proffesional ovens are convection ovens. How does this work exactly? I know what convection is - hot air rising and transferring with it the heat higher up. But what is the difference between a commercial/proffesional convection oven and a home electric oven? Doesn't any oven that has a heating element at its bottom heat at least partially by convection? What is the main strength of a commercial oven?

 Thanks

Ivri

demegrad's picture
demegrad

Wow, I mechanical engineering question, I hope I can answer it clearly.  So to define the question, you would like to know what is the difference between standard and convention ovens, also you want to know what would be the difference with home and professional ovens.

 So for the first question.  All oven "technically" operate with convection.  The word convention just refers the manner in which heat moves from the coils to the food.  More specifically, heat convection is the transfer of heat by a fluid, the fluid in this case is of course air.

In a standard home electric oven there is a heating coil located in the bottom of the oven, a current is passed through this coil and it gets hot.  This causes the air surrounding the coil to heat up and become less dense, and less dense air rises, further causing the denser cold air to fall torward the coil and heat up and the cycle continues.  This is called "natural convection", because the motion of the air is caused solely by the heat.

Ovens referred to as "convection" ovens would be more properly called "forced convection" ovens.  These ovens usually have no coil on the bottom, but a coil in the back, behind of the oven's chamber, and has a fan further behind the coil.  The fan forces air to pass over the coil, which is where "force convection" comes from.  This is a far more efficient method for getting heat from the heating coil to the oven's chamber.  It is also undoubtedly better at keeping the temperature within the oven's chamber more uniform than a standard oven, e.g. Even heating!!!

 As far as "professional" ovens.  I don't really know much difference except I'm sure pro ovens have better ceramic materials in the heating coils to last longer, they're bigger to hold more food, and more insulation.  I think pro pizza ovens have a lot of heavy ceramic materials that form the bottom of the ovens.  Maybe someone else can shed better light on this.

demegrad

http://www.demegrad.blogspot.com

ivrib's picture
ivrib

Thanks Demegrad for the useful information.

What exactly does the ceramic do for the heating coils and for the bottom of the ovens?

Ivri

JERSK's picture
JERSK

 

Commercial ovens come in many different varieties. They don't have more insulation then regular home ovens. Most are gas and don't have heating coils. Commercial electric ovens are real energy hogs and the ones I've seen and used require a 3 phase 220V hook up. What distinguishes commercial ovens from home type ovens is size and the amount of BTUs. Basically they are bigger and more powerful. most states have regulations against selling commercial ovens for home use and your insurance company would probably cancel you if they found out. This is due to the lack of insulation which makes them more of a fire hazard and increases the risk of being burnt, especially with children. Commercial convection ovens can be gas or electric. Pizza type deck ovens are usually gas and are particularly good for baking bread because of the stone deck, though some are steel. Other commercial ovens are really just big home style ovens or ranges. The ovens are big enough to hold standard size restaurant sheet pans, but they aren't insulated. Companies like Viking and Garland sell commercial style ranges for home use with better insulation. Convection ovens are good for some things, but not everything. The theory is there are fewer hot spots, but that's not really true. I've always found hot spots in them and have to rotate pans quite a bit. They're noisy because of the fans and some you can't turn the fan off. You generally have to cook 25 Degrees lower than normal. Things that cook quickly or need a fairly high temperature work best. They roast meats well, but the fan spatters the fat. Cookies do pretty well , but muffins or things that have a high quick rise tend to get blown over. I've never tried them for bread, but I've read people on this website saying they work well. Forget anything that would require a long slow cooking. Brick or retained heat masonry ovens work really well for bread , but require wood. Great ovens and you can buy them in kits for home use, though they have limited home use, pizza and bread mostly. They also have to be heated beyond the point you need to cook and you cook on the cool down cycle, tricky and take some getting used to. I built a cly one in my backyard, I love it but I can't use it for everything , or at all in the winter here in Maine.They cook by convection, conduction and radiation. Which brings me back to the original question. Technically ,home and commercial style range ovens cook by  radiation. There is one heat source and the heat radiates from there with minor amount of convection involved.The radiation isn't as good as a stone oven because the oven walls are basically sheet metal and don't retain much heat. They are good all purpose ovens though and you can use quarry tiles or pizza stones in them to get some hearth type efffect. Pizza ovens cook primarily from conduction. The item being cooked is placed on the oven floor and heat is conducted into it with some additional radiant heat. There is also what is called a commercial deck oven which is quite different than a pizza deck oven. They are steam injected and are a masonry oven, but they are gas fired. These oven are really good for baking almost anything, but they are huge and expensive. Really only good for large scale commercial bakeries. There's also rotating deck ovens for commercial use. They have maybe 8 or so large decks that rotate around the heat source. Again, really big and expensive and only good for large scale commercial use.

pumpkinpapa's picture
pumpkinpapa

I picked up a used Hobart electric convection oven with the boiler unit. Great price and it is insulated too.

I didn't even think to ask about power requirements, I knew it would be a 220 setup which we run everywhere here on our farm. But as you stated the ovens are 3 phase like this one I have, but I know where to get 2 phase models now (or is it 1 phase).

Plus it's a little big but that isn't a problem.

Even better, now we have a new gas well on the property so we can look at gas ovens too.

Now I just have to sell the Hobart ;) 

ElaineW's picture
ElaineW

Hi,

You might want to check out this site: http://ths.gardenweb.com/forums/appl/

They get all sorts of appliance questions. I own a 48" Viking Dual Fuel Convection range and I love it. When we were looking for a range we were told that you cannot put a commercial range in your home. The powerful ranges made for residential use has more insulation. We just wanted something without all the electronics. We looked at Wolf, Viking, and I think Monogram by GE and the Viking was the only one without electronics other than the burners.

Elaine

Mike Avery's picture
Mike Avery

A friend did the same thing you did.  And there are options.  Options that are less expensive than getting another oven.

The first option is to look into getting three phase run to your home.  Honestly, that will probably be cost prohibitive, but asking the electric company and your electrican is free.

 

Next, look into a phase inverter or three phase converter.  It will take your 220vac and turn it into three phase.  They are reasonably priced and last a long, long time.

 

Finally, look into re-wiring the oven for single phase.  The heating coils don't care if they are fed with single or three phase electricity.  It's usually pretty easy to rewire the oven.  That's what my friend did.  It took somewhat longer for the oven to warm up, but it held temperature just fine.

 

Mike

 

pumpkinpapa's picture
pumpkinpapa

Wow Mike, what a great resource you have provided! This gives me so much more to work with and with all the electricians on the farm I'm sure we'll be able to work something out.

I didn't know you were the author of the Sourdough home, a resource I have sampled much in the past. Though my first visit was because I was setting up Apache myself ;)

Thanks again, and I'll be sure to let you know how it works out.