Howdy,I have a new Mastertemp 400 unit that I installed as a replacement for the old Sta-Rite Max-E-Therm 333.The unit fires up but does not heat the water.The following happens:- I push SPA button (Temperature is set to 104F), blower activates and 30s later heater fires with a wooopf. Exhaust gets nice and hot so unit is producing heat- Pump is pumping water through the unit, the flow rate of the pump is 60-70 GPM. There is no bypass, all the water is going through the unit as the spa has massive water movement. There is no by-pass installed- No LEDs come on, the only lights on the display are the green SPA light and the yellow heater light- Heater works as it should as far as I can tell, but the water going through it does not get hotThe heater burns and runs, it does not shut off, only when I manually shut it down.Any ideas why the water does not seem to be going through the coils?Any help would be great, thanks!Michael