I have an Open loop, WF Envision 5 ton, dual speed system, with a 20kW electric backup installed. I have a question, why does the unit require the coil to have power to turn on. I have a large generator, that will handle the furnace, well pump,...., but not the electric backup. I know that I could still power the electric backup and lock it out from be used by the furnace, but it appears in the wiring diagram that when the backup is installed, it is hooked into the power solenoid instead of two wires. Why? Thanks, Rob

Not sure what you mean by "hooked into the power solenoid instead of two wires"

On my old house blower and 24 Vac control transformer were on same circuit as strip heaters, but that was a split system and thus typical.

My guess is this is a design feature WF wants for safety, or at least to cover their end of the liability in case there's a fire resulting from the Aux heating strips being powered without the ECM2 blowing.

Two distinct changes are made for the Envision with Aux heat strips, versus an Envision w/o the heat strips:

1.) Power for the ECM2 motor is wired to the Aux heat strips source power.  In an Envision w/o heat strips power for the ECM2 motor is factory wired to the same power supplying the compressor.

2.) Power for the 240-to-24 VAC transformer is likewise changed to be connected to Aux heat strips power.

My guess is you could go into your unit and reconnect the balk/wh and gray/wh wires between unit power and the ECM2/transformer, but, my guess is you'd put yourself at an insurance risk if there were ever to be a fire, regardless of how the situation is rationalized.

I would think a better course of action is to leave power connected to the Envision as specified in the Installation Manual, including removal of the 2 wires noted in the above paragraph (Note 4 in the wiring schematic), and instead lock out Aux heat via a tstat setting, or tstat wiring change.  In other words, make your adjustment on the low voltage side, via either tstat setting or tstat wiring.

Hope this helps.

Best regards,

Bill

I agree with your suggestion about using the the tstat to lock out the aux. heater, but i still don't understand WF's reasoning. If no power is to the aux. coil, then i would think that one should be able to operate the unit as if no coil is installed. They could wire it so that the coil couldn't be energized without powering the ECM. Am I missing something in the logic?