LC+ will run at anything over 8VAC, however the max speed will be limited by how much of a load you are pulling. Just the engine? 9 VAC will give you full speed. Add a couple cars and you may need 11-12 vac. through testing I've found that even pulling a very heavy load, 12 VAC is enough to provide the full range of speeds. The smoke unit is then the limiting factor, as it does not really work below 14 volts and needs 16 volts to put out full output when the engine is run by remote. For some reason when run conventional the smoke unit works with about 2 volts less on the track. End result, if you're not sure how much voltage is on the track, error on the side of caution and turn it up only enough to give you the range of speed you desire, and the volume of smoke output you like. 16-17 volts is plenty.
JGL
Edit: I missed the part about the ZW-C. The ZW-C doesn't control actual voltage the way a traditional transformer does, so from a technical stand point, the engine can see 'full power' even when the throttle is set to a lower level. With the PH180 bricks, however, you should be fine at full voltage, and the ZW-C is likely to drop the voltage by about 0.6 volts anyway, so full throttle will be fine. lower voltage will probably also be fine, though I've not done any tests with a 'chopped wave' transformer to confirm this.
