For those ovens that are fan assisted you will find that the heating element/gas flame and fan are separate usually the heating source is at the bottom of the oven and the fan at the back. Whilst if you have a fan forced oven then you will find that both the heating element/gas flame is surrounded by the fan. In some cases you may even find that your oven is a combination oven meaning it is both a conventional and convection oven. Then there are some combination ovens that are both a microwave and convection oven as well and this has a number of advantages over a normal convection oven, not only can food be cooked quicker in it but you will discover that even less energy is used than a normal convection oven.
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