nest.class.php
public function setDualFuelBreakpoint($breakpoint, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        if (!is_string($breakpoint)) {
            $breakpoint = $this->temperatureInCelsius($breakpoint, $serial_number);
            $data = json_encode(array('dual_fuel_breakpoint_override' => 'none', 'dual_fuel_breakpoint' => $breakpoint));
        } else {
            $data = json_encode(array('dual_fuel_breakpoint_override' => $breakpoint));
        }
        return $this->doPOST("/v2/put/device." . $serial_number, $data);
    }
public function setDualFuelBreakpoint($breakpoint, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        if (!is_string($breakpoint)) {
            $breakpoint = $this->temperatureInCelsius($breakpoint, $serial_number);
            $data = json_encode(array('dual_fuel_breakpoint_override' => 'none', 'dual_fuel_breakpoint' => $breakpoint));
        } else {
            $data = json_encode(array('dual_fuel_breakpoint_override' => $breakpoint));
        }
        return $this->doPOST("/v2/put/device." . $serial_number, $data);
    }
Change the dual-fuel breakpoint temperature.

@param float|string $breakpoint    DUALFUEL_BREAKPOINT_ALWAYS_PRIMARY, DUALFUEL_BREAKPOINT_ALWAYS_ALT, or a temperature: thermostat will force usage of alt-heating when the outside temperature is below this value.
@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.