Knowing now that you only have two zones helps. The bypass size must be selected to accommodate bypassing the excess air when the smallest zone is calling for cooling. You never mentioned whether your bypass was motorized or barometric. The barometric tend to work better on modulating/variable speed furnaces in most cases since, the motorized/pressure sensing often continues searching for proper position as the variable speed blower constantly changes slightly. The 2" upsize may be all you will need and perhaps not, not knowing your zone and duct sizes. Does your zone system panel have a plenum temp sensor for heat & cool? If not, it should to keep the heat exchanger from getting to hot, limit cycling or temp across a-coil during AC from getting too cold while the excess air is bypassing. HereÂs a thought; many people have solved their airflow/insufficient duct sizing by simply installing a bypass humidifier. Not that you need to install one but, you can appreciate the bypass benefits by simply adding an additional 8" or so pipe between the supply and return ducting. With a manual damper on it you can adjust it as a primary or secondary bypass in conjunction with your zone bypass damper.

Dear Pedalbrake37, I am a new homeower, and I found your post here with your Ducane CMPE075U3B natural gas furnace. I have the same model but it's 6 years old now. It stopped working this morning and has similar symptom as yours. When I turned it on, just heard the hummmm sound, but the motor is not blowing. I opened the panel in the middle, the black round thing (A in the photo attached) which I saw was spinning is now not moving at all. I called the company who had a checkup service about 40 days ago, the technician said the motor is out and need to replace it. He said the unit B is hot and I touched it, yes, it's warm. But when he turned my thermalstat to cool, and turn fan to on, it starts to blow with normal big noise. So I have a few questions here: 1. Is it the problem with the blower motor? Or like your case, the capacitor? But I can't find the capacitor there... 2. What is the black round thing A? It's not spinning, and I am sure it's the problem with it. 3. What to check in this situation? We have a 8 month daughter and it's so cold now but I don't want to be fooled by the tech guys with $1200 to replace the blower motor. Could you help me with it? Thank you so very much! Simon

Both head gaskets have been replaced. I thought this when I first started having problems. I changed them then and no difference. They were also changed when I had the rings replaced. Again no change in the amount of oil being used.

I looked at the manual, and I interpret the diagram you mentioned as how to convert an existing two stage cooling that uses a PSC motor to the Evergreen two stage cool. The diagram shows how to wire the high voltage, but not the control voltage. I think they assume you already have the control wires in the harness coming from your furnace control board for two cooling stages. Those control wires would have gone to fan relays in the PSC setup. Is this a DIY project, or are you going to get a contractor familiar with the Evergreen to do the conversion? If this is DIY, I can point you to a website that answers DIY and there may be someone who has done what you want to do, If contractor, make sure he knows not only how to convert from PSC to ECM, but from one stage cooling to two stage. In general, it seems like the Evergreen can be used for multi speed applications, so the pieces are there. It just will take some knowledge of how to make it work.