gas oven

the infos?

A gas oven works by burning natural gas (or propane, if it's a propane stove).

When you turn on the oven, a valve opens, and the gas starts flowing. An electric ignitor lights the gas. A thermostat tracks the temperature, and when it gets high, the gas turns off, and when the temperature gets low, the gas turns back on again (just like a furnace).

Some older gas ovens have a pilot light instead of an electric ignitor (a small flame is always burning below the oven floor, and when the gas is turned on, it ignites). Some really old gas ovens don't have any kind of internal ignitor at all, and need to be lit with a match.

jenn

-- Jenn Ridley snipped-for-privacy@chartermi.net

i'd like to know how's the gas oven works?any web site or someone could give me the infos? thanks alan

give me the infos?

There is a piece in the oven that measures temperature, call it a thermometer. There is a connection between the thermometer and the gas supply, the gas valve. There is a temperature control knob on the front. There is an on-off method built into the oven. This is controlled by the control mechanism.

Here's how it works.

You set the temperature and turn the oven on. Say you set it to 350F.

The gas valve opens and the gas ignites, whether by pilot light, electronic ignition or match.

The oven burns some gas and the oven heats.

As the oven heats, the oven thermometer measures the temperature and reports that back to the control mechanism.

The control mechanism is set to respond to a range around the temperature you set. It will go on at a temperature slightly below what you set and off at a temperature slightly above the temperature you set. In this instance, let's say that it is set at 10F above and below the temperature on the knob.

As the oven heats, the thermocouple reads the temperature. Then the temperature gets to 350 + 10F, it will stop heating. As the oven cools, it will continue reading the temperature. When the temperature gets to 350 -

10F, it will turn back on and heat until it hits 350 + 10F. And so and so on and so on.

The oven is never really "at" 350F except in passing through on the way up and down, but it averages 350F over the course of the baking period.

Barry

The thermostat is an electric device. You can probably buy one and install it yourself, if you have the manual or can get it online and you can find the part. If you can't do this, you'll have to buy the part and have it installed for you. I have done this on electric ovens, when it's just a matter of replacing a burned-out element or thermostat. On the other hand, electricity isn't explosive and electric equipment isn't as stringently covered by various Building Codes as is gas equipment. ("I smell gas." is the surest way to get a bunch of people off their duffs and into your house pronto. when was the last time anyone said "I smell electricity?")

The part will probably cost about $30 and the service call will be around $100, both plus tax. Total cost around $150, just as a guess. As an example, I remember the heating element on a Thermador electric oven cost around $50 and took about a half-hour to replace.

I have 38 gas stoves with ovens and 4 325,000BTU boilers. I do not do any of my own gas-unit repairs, even though I am a very good mechanic, at least on automobiles and other machinery. By the nature of your questions, I assume you are not a qualified mechanic or contractor.

I also do not repair gas ovens. I replace the stove when the oven fails. I figure that fixing an oven is just wasting money. A gas oven has a service life of 10-20 years, depending on use and quality, so if it fails after 12 years, that's it. We buy good quality, reliable stoves and spend anywhere from $325 to $500. (30", 4 burners, standard oven with broiler, pilot light or electronic ignition).

As for modifying an oven to add a broiler, forget it. There are so many possible Building or Municipal Code violations here that I can't even begin to list them. If you buy a new gas stove/oven, make sure that your installation meets your local Code.

Barry

how does the thermostat control the gas valve when tempreture overshot? the reason i asked for the upper gas burner(element)is bcos some baking need upper tempreture more than lower temppreture,in electric oven you can have seperated upper or lower element,but in gas oven case,how can we get it? I was told that industrial/commercial gas oven does have upper and lower burner element,is that right?cos i haven't seen one like that before. i feel that gas oven tends to generate more moisture(gas?)than electric type(tends to be dry type)and resulting of different quality for the baked product. is the any book or web site i can learn more about gas oven? thanks

My experience and observations are that the lower element does most of the work in both gas and electric. The upper element in an electric oven is for broiling and, maybe, preheating. In the gas ovens we have, the lower burner does the work, while the upper burner is for broiling.

The thermostat controls the gas valve by shutting it off and turning it on -- shutting off the flow of gas, thereby turning the oven off, and restoring the flow of gas, thereby allowing the oven to turn on. Both types of ovens operate in on or off mode, there is no such thing as an oven that's "on low." When an oven is on low, it is set for a low average temperature.

I'm not aware of any recipes that require upper or lower heating, except for broiling.

I know nothing about industrial gas ovens. I've used and managed very large electric annealing ovens, but those were used in temperature ranges of 1300F and annealed brass and copper by the ton.

As for the moisture generated by the gas oven as opposed to the "dry" heat of an electric oven, I wouldn't worry about it. You'll probably find that the moisture released by the baking process itself overwhelms the bit of moisture generated by burning gas, and that the gas-generated moisture dissipates rapidly. This will undoubtedly start a thread/flame from those who will claim that the amount of moisture is significant, since I remember a thread recently that pounded this topic to death, but it's not worth thinking about.

As for a web site or book, I haven't looked for any. You might try a google search on oven gas control and see what pops up. You could also check out a boiler manufacturer, ours is Slant Fin, and see what they have in the way of discussion. The principles of an oven and a gas-fired boiler are identical.

Not to belabor a point, which I am, but we have 4 boilers in series with a computer control that fires them in sequence. The control process works by measuring the ambient (outside) temperature. It the ambient is above 60F, nothing happens. If the ambient is below 60F, then the controller measures the ambient and the discharge water from the boiler. It checks the temperature set on the control panel and the control band. There is another control, one that moves the set temperature up and down by a ratio, but let's not get too confused here.

Consider an ambient of 25F (today's temp), a base water temperature of 110F and a band of 3F. These are my conditions today.

The control program is set to raise the temperature of the water to the base water temperature plus 70F minus the ambient. Today, this works out to 110

+70 - 25 => 155F. The control band is the tolerance within which the discharge water must be maintained. I have a temperature gauge on the discharge pipe and a temperature gauge on each boiler on the discharge side. I know that in this temperature range, one boiler will be sufficient to raise the total water flow by about 10F, which is about the temperature drop between output and input; one boiler will, therefore, just about maintain the desired temperature under these conditions.

So, when the water temperature falls to 155 minus half the band, or 155 minus 1.5 degrees or 153.5, the boilers start to come on or fire. They will go on, one at a time, and continue to come of in sequence and to fire until the water temperature hits 155 plus 1.5, or 156.5F. Then they will start to shut off, the first to fire will shut off first. There is a 2 minute lag built into the firing and shutting off process to allow the system time to stabilize.

A kitchen oven works the same way, except that it has only one heating element. There is a desired temperature, a control band, and a mechanism for turning the heat on and off.

Barry

replacement