Hi Jon,
Try this code, it should turn all relays on for 3 seconds and then off for 3 seconds.
byte relay_address1 = 1; //Tech sheet said 8 was default
void setup(){
Serial.begin(9600);
}
void loop(){
Serial.print(relay_address1, BYTE); // send relay module address
Serial.print(100, BYTE); // All relays on
delay(3000);
Serial.print(relay_address1, BYTE); // send relay module address
Serial.print(110, BYTE); //All relays off
delay(3000);
}