White-Rodgers model 50A50-206 Troubleshooting Guide

Anyone know where I can find a copy of Troubleshooting Guide for a White-Rodgers model 50A50-206 hot surface ignition control for my furnace?
I checked the White-Rodgers web site, but that model is superseded and they don't have any information on it.
The new model they recommend to replace it is quite different and I doubt the info on that one would apply.
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Just buy the replacement, they aren't worth trying to repair.

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I'm not trying to repair it. It works fine. I just want to know the theory of operation - e.g. what sensors does it test, and in what order.
For example: If the ignitor is burnt out (open circuit), does the control detect this and refuse to open the gas valve? Or... does it open the gas valve, and then detect no flame, and turn the valve back off?
Stuff like that.
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Almost everything goes through that board. There should be something like a sequence of operation in your owners manual. Something like "Igniter Lights" - "Yes" or "No".

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I guess I wasn't clear. I do not have an "owner's manual". I never got one. I do not know who installed the furnace.
Even if I did have an owner's manual, I doubt the information I am seeking would be in there.
For example: If the ignitor is burnt out (open circuit), does the control detect this and refuse to open the gas valve? Or... does it open the gas valve, and then detect no flame, and turn the valve back off?
Stuff like that.
EJ
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wrote:

Why does it matter? You got lucky and fixed it without killing yourself. That should be enough to satisfy you.
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wrote:

I only know about stoves, but stoves do it a third way. (There is almost always, in every area of thought, more than two ways.)
Ini a stove with a hot surface ignitor, the control supplies power to the ignitor/valve circuit, and when current through the ignitor is sufficient, it allows the valve to open.
If the ignitore is burned out (rare, right?) no current flows through the valve becuase it is in series with the ignitor.
Maybe furnaces are different.

Remove NOPSAM to email me. Please let me know if you have posted also.
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If the igniter doesn't light, the gas valve will not open at all.

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<<If the igniter doesn't light, the gas valve will not open at all>>
That sure sounds like the safe way for it to work.
And it seems to agree with what I observed: the igniter was not glowing, and I couldn't smell any gas at all.
I do wonder something though. IF the gas were to turn on (but not ignite), would the smell be detectable? Or is the vent motor so effective that all the unburnt gas would be vented and you wouldn't smell it. Just wondering if anyone has any experience with such a situation.
EJ
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Ether Jones wrote:

It isn't necessarily the correct info. The replacement for your obsolete control uses timed sequences only. As a supposedly improved version this seems to imply that the original wasn't safer than the replacement, or IOW, the old control likely uses timed sequences as well. The gas valve is opened 17 seconds after the HSI is energized.
BTW, the flame is detected via flame rectification, in exactly the same way that units with separate flame probes detect the flame. The position of the HSI in the flame is thus very important. 1/2 to 5/8 of its surface should be in the flame.
Richard Perry
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<<The gas valve is opened 17 seconds after the HSI is energized [even if the igniter isn't glowing]>>
Wow. I bunch of questions come to mind, if you would be willing to answer:
- assuming the igniter is faulty but the control opens the gas valve anyway, how long does the control allow the gas to flow before it detects "no flame" and shuts it back off?
- does the control recycle through the ignition sequence, and if so, how many times does it do this before giving up?
- what happens to all the unburnt gas? is the vent fan supposed to be designed to have sufficient suction to thoroughly scavenge it and blow it out the vent so none accumulates inside the home? (i.e. is that the basis on which such a design is deemed safe?)
- where did you get the "17 seconds" info from - your direct experience with this control, or from some white-rodgers documentation?
Thanks,
EJ
-------- (put "[nofilter]" in subject if sending email; otherwise it will be blocked)
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Ether Jones wrote:

Try some creative Googling. FWIW, WR has a website.
Richard Perry

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<<Try some creative Googling. FWIW, WR has a website>>
I always Google before posting in the newsgroups. Don't want to abuse the generosity of the good folks here who are willing to share their knowledge.
The WR website says the model 50A50-206 is obsolete, and they removed any documentation that might have been there at one time. I was hoping someone might have a copy squirreled away.
EJ
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RP wrote:

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With all of the safety controls on 90+ furnaces, I doubt if it's possible.

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