Lp ga oven stopped baking.

earl burnermann

Last night we lost gas to oven while baking. Could see the hot surface igniter glowing but no flame. Found the wiring diagram and saw that the HSI was wired in series to the gas valve. Had 120 volts to igniter, 0 volts coming out the other side. Checked the resistance to the gas valve coil and had 1.3 ohms. Switched the broiler HSI to the bake and the wife finished baking the pie.



So it looks like the HSI is also working as a safety. Could someone please explain? I am only used to seeing them wired in parallel to a heating unit with a flame sensor as the safety.

earl burnermann

Problem solved

So I found out that the voltage travels through the HSI and activates the gas valve. The valve has a heater that delays it's opening. As the HSI looses it's strength, the time to open the valve increases. Eventually the HSI will wear out to the point that, although it glows, it will not send enough voltage to open the gas valve.

Tim McElwain

It actually works this way

The igniter when cold has a higher resistance and as it heats up the resistance drops. This is used on gas ovens to allow the igniter to get hot enough (1800 degrees) to safely ignite the gas, The applied voltage (120 volts) in conjunction with the amperage will allow this to happen. As the igniter wired in series with the valve decreases in resistance it allows more current to flow (around 3 amps) which is the required amperage for the gas valve to open. The valve opens and the gas is ignited by the igniter.



There is a tendency on these systems to do the following, the igniter is glowing but the valve will not open so folks will replace the valve only to find it still does not open. The problem is as the igniter gets older it tends to not decrease in resistance and there fore sufficient current to open the valve is not available. The problem is that the igniter is faulty and needs replaced even though it still glows. An amp meter is a big help in diagnosing these problems as you should see 3 amps of current or higher if the system is working properly. No 3 amps replace the igniter.



This is the only gas system that has loads in series, the igniter and the valve.

Harvey Ramer

That

is very interesting Tim. It's almost like using the igniter as a potential relay.



Good Stuff! 

Tim McElwain

This is also a very

interesting illustration of Ohms law, as resistance decreases amperage increases with voltage remaining constant.

Harvey Ramer

Here is the part that has

always irritated me Tim.

Low resistance = more resistance to current flow.

High resistance = less resistance to current flow.



I think that has confused a lot of people already.

Jean-David Beyer

the part that has always irritated me

"Low resistance = more resistance to current flow.

High resistance = less resistance to current flow.



I think that has confused a lot of people already"



I think what is most interesting is that those two statements are untrue.



Ohm's Law is R = E / I

where R is the resistance

           E is the applied voltage

           I is the current that will flow..



Bu simple algebra, we can re-write that as:



I = E / R



from which one can see that (for a constant applied voltage)

more resistance results in less current flow

less resistance results in more current flow

Harvey Ramer

That's exactly

what I just said Jean. Look closer and think harder ;-)

Jean-David Beyer

That's exactly what I just said

"That's exactly what I just said Jean. Look closer and think harder ;-)"





I must understand American English differently from you. It seems to me what you said is the exact opposite to what I said.

Harvey Ramer

Well

I guess I misspoke. I was thinking about power consumption when I said current flow.



Higher resistance = less power consumption when a circuit is engaged

Lower resistance = more power consumption when a circuit is engaged



Higher resistance = less conductance and therefore a lesser flow of electrons through the resistive device and lower resistance is just the opposite.

ChrisJ

Eh

Harvey,

Look into how a transformer coupled vacuum tube amplifier works and it will really bake your noodle.    Or the fact many circuits look like different impedances at difference frequencies.  An audio speaker may have a DC resistance of 6 ohms and yet depending on the frequency it may operate like anything from 4 ohms to 30 ohms.

I spend much of my life working with electronics and still learn new things all the time.

SWEI

Funny

how analogous hydronics and electricity turn out to be.  Once I figured that out, everything just fell into place.

bill_105

But I'm wondering...

Just how did the pie or cake turn out:)?

Harvey Ramer

Chris

I'll make it a New Years resolution to study that a little. It's to late in the year to have my noodle baked ;-)



In the meantime, I'm with Bill. Oven works! How about those cakes and pies?





Oh by the way Chris. Maybe you could explain a little mystery I have.





Setting and equipment;

Chicken barn, proximity sensor, 120v Flouresent lights t-8



Problem;

When you turn on the Flouresent lights it triggers the proximity switch and causes the feeding equipment to turn on.



Solution;

I moved the single pole breaker that powered the Flouresent lights to the opposite power leg of the proximity switch. It is a 240V service and once I switched legs, problem solved.



Mystery;

Why???

earl burnermann

The pie

was very tasty!

ChrisJ

Wow

Hi Harvey,



Honestly I have no idea.  The only guess I have is high frequency noise from the fluorescent lights causing interference.  There is a chance installing something like a few low value high voltage capacitors from the hot to ground would have fixed the problem.  Something like a few 0.01uf 250v+ ceramic capacitors could have worked.  What they would do is take the high frequency noise and short it to ground while not passing any 60Hz due to their small size.  



If you do a search for "ac line suppressing" you will find all kinds of info on this.  You will find such things even in 1950s audio equipment.