public function setEcoTemperatures($temp_low, $temp_high, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        $temp_low = $this->temperatureInCelsius($temp_low, $serial_number);
        $temp_high = $this->temperatureInCelsius($temp_high, $serial_number);
        $data = array();
        if ($temp_low === FALSE) {
            $data['away_temperature_low_enabled'] = FALSE;
        } elseif ($temp_low != NULL) {
            $data['away_temperature_low_enabled'] = TRUE;
            $data['away_temperature_low'] = $temp_low;
        }
        if ($temp_high === FALSE) {
            $data['away_temperature_high_enabled'] = FALSE;
        } elseif ($temp_high != NULL) {
            $data['away_temperature_high_enabled'] = TRUE;
            $data['away_temperature_high'] = $temp_high;
        }
        $data = json_encode($data);
        return $this->doPOST("/v2/put/device." . $serial_number, $data);
    }