I have added some code in the "temperature.cpp" for have the possibility of control the time of the states with the heater drived by relays, with this feature now it is possible use PID function in conjunction with relay to control the temperature. I have made some tests and the temperature stay always in the range of +-1°C from the setted temp.
There is the possibility of turn on this features adding "#define SLOW_PWM_HEATERS" in Configuration.h