code: public function setFanModeMinutesPerHour($mode, $serial_number = NULL) {
          $modes = explode(',', $mode);
          $mode = $modes[0];
          $duty_cycle = $modes[1];
          return $this->_setFanMode($mode, $duty_cycle, NULL, $serial_number);
      }
docs: Set the thermostat-controlled fan to be ON for a specific number of minutes each hour.
  
  @param string|array $mode          One of the FAN_MODE_MINUTES_PER_HOUR_* constants.
  @param string       $serial_number The thermostat serial number. Defaults to the first device of the account.
  
  @return stdClass|bool The object returned by the API call, or FALSE on error.