It's an amperage issue, not a voltage issue. Theoreticaly, you could have a 220v 15a hot tub. this spa will not run a single 220v 2 speed motor on high speed with the heater onsince there is not enough amperage to operate both. Jacuzzis 2 speed motor draws 11 amps on high speed, most circuit breakers will trip when load exceedes 85% of the rated amperage, so the heater would become disabled to allow for jete function in this hypothetical spa.
In order for some Sundance models to allow the heater to come on when all pumps are running full tilt, the owner must have a jumper set on the control board, which requires a 60 amp GFI. When set to 50 amps, the heater on these spas won't come on if both pumps are running full speed.
Don't know if this is unique to just Sundance, though.
HUh. I thought all 220 tubs could run the heater, and all the pumps full bore without an issue or upgrade/mod.
I know on my 220 Caspian, it's not a problem (that's why I made sure I had a 220 tub). I can feel the heated water flowing into the tub via the floor drain.