Sunday, June 1, 2014

Converting a Lennox Furnace with the Piggybacked Ignition Module to the Honeywell S8610U1003 Control. (Techs Only Please!)


*******WARNING! If you are a homeowner reading this, the furnaces with this control are well past their service life. The technician doing the repair MUST inspect the heat exchanger for failures thoroughly before doing this and any other repair to this piece of equipment. The furnaces included, but not limited to, Lennox G11 and G12 models with the ignition module mounted to the gas valve. These also have the Dura Curve heat exchanger that is prone to cracking along the rear of the curved sections where the welds are. Once these are cracked, they cannot be repaired and must be shut down and replaced per AGA guidelines, state and local safety codes as well as common sense. Again, many of the parts on this piece of equipment are obsolete as they were made 30 years ago and this repair could cost in excess of $500. This is for a furnace that will fail anyway. From my experience, people will replace everything they own in the course of seven years including their automobiles, which cost ten times as much as a properly installed furnace. Even a base 80% efficient model should cost less installed than high end plasma television. The furnace will save you hundreds of dollars a year in heating costs and possibly tens of thousands in home repairs and medical costs. I've walked into these homes where they have a brand-new car, high end infotainment systems and the furnace over 30 years old. You know who you are, so forgo the TV and replace the furnace.******

******Disclaimer, this article is for informational purposes and the job is best left to an experienced technician only. Even then, other parts can be damaged and instructions need to be followed to the best of your ability and circumstances determined by your best judgment. Personal injury, death and property damage can result from working on heating equipment even when repairs are done to the best of your ability and instructions are followed to the letter. Perform this and all repairs at your own risk.******

Follow the instructions per the Honeywell module, but you will need to remove old module off the gas valve with the two screws and disconnecting the red, blue and black wires. Mount the new control to the upper right corner of the inside panel over the heat exchanger so the wires off the gas valve can reach. Hook up the three wires from the gas valve to the new unit. Follow the wiring diagram. Now for the tricky part. You MUST remove the ground pigtail from the neutral wire on the transformer or you will fry that and the thermostat. Better off taking that ground wire and using this as the burner ground on the new module. This is it boys and girls, and probably my last post for HVAC repair for a while.



This is the typical wiring diagram for the furnaces in question. Note that other diagrams will differ.

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