I have a Superstor Contender hot water heater with a Thermomax  SMT100 controller, installed in 2009. We are in the Pacific NW. On hot sunny days my hot water tank overheats/ over pressures and  releases the safety pressure valve on the tank to discharge about a gallon of water outside . How do I adjust the settings for the tank , differential temp and collector temperatures to prevent the tank from getting to hot. Is  it a problem with the controller? We live on an island and do not have anyone in the  area to work on our system.

I have already replaced the pressure relief valve on the tank.