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Smart Valve- Armstrong furnace Dead
were Armstrong dealers, which is how I learned about the 80% bulletin, plus a little first hand knowledge too.
Now I will have to go dig in my Armstrong file for bulletins and see if I can find the bulletin on the 80% units and see if the horizontal 90% units are mentioned and I missed it or if it is a sepparate bulletin I never received. Either way I will remember what you said.