Yes you could and it's been done. However, I am not aware of any field install kit to accomplish this so it would require an advanced knowledge in circuits and electric to accomplish this. Along with applying the correct sized motor control via relays and contactors. Keep in mind, you must energize and de-energize various motor circuits when a call for fan only/heat/ac in correct sequence or you risk motor/circuit failure and/or fire.

whatever I find it interesting that dealer plans to upgrade sizes but you have said nothing about whether ductwork system b oth supply and return has been inspected thoroughly to see if it can handle additional CFMs. Just as important as size of systems. what size heat strip for each system? here are the numbers. BTW, AmStd is excellent HVAC. 3436397 Active Systems ALLEGIANCE 15 AMERICAN STANDARD, INC. 4A7A5042E1 4TEE3F40B1 40000 13.00 16.00 1421684 Active Systems ALLEGIANCE 15 AMERICAN STANDARD, INC. 4A7A5048A1 4TEE3F49B1 48000 12.00 15.00 1 these are AC condensers, not HPs correct? the 3 1/2 ton system qualifies for tax credit, the 4 ton does not. what stat was quoted? "We think by relocating them to the garage that this will decrease my electric usage." That's an interesting statement. IMO

Actually no - XV is variable speed. Multi-speed blower control is possible and was exactly what I wanted. Trane tech support provided my installer with the wiring change below. The XL multi-speed blower works perfectly with XR 2-stage compressor. I have ideal CFM in my home with 18 and 21 degree temperature deltas on stage 1 and 2 respectively. WIRING GUIDE Thermostat = Furnace = Condenser R = R = N/A (unless condenser requires) Y1 = N/A = Y1 ( wire nut to bypass the furnace connector) Y2 = Y = Y2 G = G = N/A W = W = N/A C = C = C Y1 bypasses furnace control board. - This leaves furnace with only G terminal energized for first stage cooling, running blower at the desired lower CFM. Y2 Is the only signal to furnace Y terminal - ensuring blower runs at highest CFM for second stage cooling.

Most residential blowers are, to the best of my knowledge, driven by induction motors in which the leading phase is self induced. Performance is speed sensitive because ultimately one is depending on the 60-Hz (50-Hz in some locales) power source to induce the leading phase. At low power levels where one is trying to induce a low speed the torque drops to very little. [I recognize that explanation is a bit deficient, so please look up how they work for a longer more accurate explanation.] In order to have good torque from zero to 100-percent, other types of motors are needed, such as the "dc" torque motor, which in modern embodiments is actually operated with synthesized multiphase ac drive currents such that the frequency fed to the motor is proportional to the rotation speed desired. The (typically permanent magnet) rotor is essentially locked to the rotating phase pattern generated by the stator. Such motors are normally used in servo mechanisms, and along with their drive electronics are not inexpensive. A true dc torque motor will use brushes, and require routine servicing. Paired low and high flow rate induction motor driven blowers can be imagined for use in-line in the ducting to expand the flow rate range, but for most this isn't necessary. kas