Honeywell RA117A Stack relay


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Old 01-01-14, 09:42 AM
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Honeywell RA117A Stack relay

I recently replaced the stack relay on my hot air furnace. I tested the oil gun by plugging into 110 volts,it ran. I tested the transformer,got about a 1 inch arc. The blower motor also works. The old relay failed so I changed it out,it worked fine for a few days,then the furnace kept running after the temp set on the thermostat was reached. The lower contact bar on the top contacts stuck (welded) closed. I believe this was the problem that caused the failure of the old relay,because the same bar was blue,like it had overheated. What would this indicate as a problem? What does the top set of contacts control? I killed the power to the furnace and pulled the contact open with a small screwdriver. I think it is OK because it came apart fairly easily,but I don't want to burn out the new relay using it. I need to fix what is causing the problem.
 
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Old 01-01-14, 11:40 AM
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You would need a clamp-on ammeter to check how much amperage the various components are drawing. Then you could find the source of the problem.
 
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Old 01-01-14, 02:20 PM
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Next time you think it's over shooting the t-stat, from the 117 remove 1 of the t-stat wires and see if the burner stops. If it does it could be you stat. If it continues to run with wire off it's the stack relay.
 
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Old 01-02-14, 12:01 AM
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In my opinion the best thing you could do is to take that ancient technology stack switch and drop-kick it into the next county. Stack switches are notorious for failing. Instead have a cad-cell primary installed, far, far safer than that stack switch.
 
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Old 01-02-14, 02:03 PM
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Furd: Agreed 110% or maybe more.
 
 

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