We have configured the network and setup the node addresses of the valves. The problems we experience is intermittent. Sometimes a valve will just fail to communicate and other times it will accept a command to open but does not send the 24Vdc signal to the solenoid. We have now constructed a test program to test the devices one at a time. But the results are the same. The installation used siemens profibus dp cable and weidmuller spur line connectors. The maximum length of the network is about 50m. All the spur lines are shorter than 1m. Is there anybody that can give me a couple of ideas as I am fresh out.