HSI will not ignite

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Old 12-30-08, 07:37 PM
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Red face HSI will not ignite

I have a TRANE / American Standard M/N FCAB 080 A30 B1 downflow gas furnace. Control board is White Rodgers 50 A 55-480. When the TStat calls for heat I get 4 flashes from the LED which indicates " Thermal Protection Device Open". The wiring diagram on the door indicates 2 temperature limit switches and 2 fusible links. I found the 2 links but can't locate the 2 limit switches. I traced the wiring from the control board to the links which appear to be wired in series and didn't find the limit switches. According to the wiring diagram all 4 devices appear to be on the same circuit. Thanks in advance.
 
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Old 12-30-08, 08:04 PM
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Is this a counterflow furnace with the fan compartment on the top and the burner compartment on the bottom? If so the additional limit switches are very likely located in the fan compartment. Remove the cover and hunt around for them. They are usually reset by pushing a small button on the switch.

Also look for anything that might have caused the fan compartment to overheat --- such as a failed blower motor, plugged filter, covered over return air duct or too many warm air ducts shuts off.
 
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Old 12-31-08, 01:14 PM
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Yes it is a counterflow I didn't see any devices that have any type of reset buttons. Mounted above and below the burners are what I believe are the fusible links. There is also a thermal device mounted to the center interior wall of the furnace just above the burners and next to the fan. All of those devices have continuity and are wired in series with each other.
 
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Old 12-31-08, 02:06 PM
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Here the installation manual for the White Roger Ignition Control Module:


http://white-rodgers.com/wrdhom/pdfs.../0037-6265.pdf


On this suggested installation, the flame rollout switches are from the Ro1-Ro2 connections, while the high temperature limit switches are wired from Hlo-Hli. You might look and see how your furnace is wired up and see if the limit switches are on another circuit like Hlo-Hli.
 
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Old 12-31-08, 02:11 PM
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Reading through the diagnostic codes on that website on page 7, the four flashes you are getting are for the high temperature limit switch, while five flashes would be for the flame rollout switches. So I'd say you need to trace out the wiring from Hlo-Hli and find out what is on that circuit, because that's where the problem should be.
 
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Old 01-01-09, 08:29 AM
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A Huge Thank You SeattlePioneer

Thank you very much for all your efforts and correspondence. After checking out the link you sent me for the PDF manual I was able to trace out the limit switches and found a bad connector on the "Aux High Limit" switch. Once I reseated the spade terminal, I powered up the furnace, adjusted the stat and .....magic. I now have heat. . Have a Happy New Year and Thanks again.
 
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