(HSI and Gas Valve Operation) Kenmore range 790.70291400


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Old 01-28-10, 05:29 PM
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(HSI and Gas Valve Operation) Kenmore range 790.70291400

Basically, how does the igniter and the "safety gas valve" work together? The igniter glows red, but the burner never turns on . Is this the igniter, or the valve? What is it that tells the valve that the flame is "on" so it stays open? No thermocouple like old pilot ranges.

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Old 01-29-10, 05:08 AM
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Hello: 594tough

Excellent Question.....

A bit difficult to explain exactly how a carbonic igniter (HSI) works but I will try and attempt to here. All has to due with electrical current and resistance values.

An HSI is designed, sized and manufactured to absorb all of the household electric current available (supplied) to it. Until it reaches a set value of resistance to the supplied voltage.

We SEE the resistance as a glow of light. The visible light also produces heat. Because the HSI is a filament element just like or similar to a light bulbs filament or element. (Depending upon which terminology >element or filament< one cares to use to describe the element/filament that we see glowing.

Once the HSI glows it's brightest, visually seen as an intense bright yellow orange color, it is absorbing all of the current available to it EXCEPT the last 5 volts. Which it then directs to the gas control valve.

If one takes a very close look at the gas valve, one should see it stamped with the voltage of or about 5VAC. That voltage comes from the HSI when it cannot absorb any more current supplied to it.

Basically and generically speaking, the HSI is a resistance to electrically current just like a light bulbs filament. Produces both light and heat to a set value and like any electrical device, returns what current it cannot use back to the electrical power source.

In the case of an HSI, it passes that extra current to the gas valve first. Before any gets returned to the power source. What we see as light (color) produced by the HSI is resistance.

As with any such electrical part, an HSI deteriorates over time. That's when the resistance becomes so high the HSI cannot absorb the full amount of current supplied to it and have any left over to pass to the gas valve. A dull color of red or a lack of bright yellow.

At the point the HSI will remain lighted but not be hot enough to ignite gas nor be passing a current or enough current to the gas valve. Valve then never opens or in some cases never fully opens. Time to replace the HSI....

Depending upon usage and other factors, an HSI usually only lasts a few years (2-5 approx) before needing to be replaced. And YES. In an oven, unlike a dryer or furnace, etc, there is no safety backup, (redundancy control using dual solenoids) so the HSI remains glowing the entire time the burner is lit and until the set temperature is reached.

Hope this explains the operation of an HSI....
 
 

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