     pinMode(relayAC, OUTPUT);
     pinMode(relayHeat, OUTPUT);
 
+#if defined(SERIALDEBUG)
     // start serial monitor
     Serial.begin(9600);
+#endif
 
     // get mode and temperature settings from eeprom or default values
     // we store a basic check pattern in first bit

    tempC = (voltage - 0.5) * 100.0;
    tempF = (tempC * (9.0/5.0) + 32.0);

    Serial.print(F("voltage: "));
    Serial.print(voltage);
    Serial.print(F("   deg C: "));
    Serial.print(tempC);

    return int(tempF * 10.0);
}

    // otherwise use the defaults and write them to EEPROM
    // note that mode only stores either "on" or "off"
    if (eepCheckVal == EEPROM.read(eepCheckAddr)) {
#if defined(SERIALDEBUG)
        Serial.println(F("Using mode and temperature from EEPROM"));
#endif
        mode = EEPROM.read(eepModeAddr);
        centerpoint = getEEPROMint(eepCenterpointAddr);
    } else {
#if defined(SERIALDEBUG)
        Serial.println(F("Using mode and temperature from defaults"));
#endif
        mode = on;
        centerpoint = defaultCenterpoint;

