SP3.0 has one water temperature sensor that must be in the lower thermo-well location. If the NTC 10K thermistor type sensor is located at the upper tank thermo-well, it must be moved to the lower well to heat the full tank, otherwise it only heats the tank top. Always check the sensor location is at the bottom,
A symptom is the floor heating coil does not get very warm, about 10-20 F less than expected, even though the tank reached full 130 F. temperature. The reason is the Thermocline of cold water has to rise to the upper sensor location to turn the compressor on, leaving the coil underneath the hot stratified layer.
Moving the sensor to the bottom well is simply pulling it out from the top and replacing in solid contact with the end of the well at the bottom. We suggest using a drop of thermal paste to improve conductivity and accuracy for the sensor - avoid any air gap at the sensor end.
Should the wire be too short, extend it by splicing in AWG20 2 conductor wire. Door bell 18-gauge wire works fine, up to AWG26 signal wire for thermostats. Soldered connections are recommended because the sensor measures resistance by water temperature change and needs to avoid aging twisted strand resistance.
This sensor location was an assembly mistake only on SP3.0, it has been fixed permanently in SP3.1.
