Control method of heating unit

Thread Starter

mztrordinary

Joined May 25, 2016
54
Hi guys

I am having trouble with a temperature control unit which is heating a process and talking back to a PLC. The trouble is that the PLC is dictating 3 different temperatures to the controller but i don't think the controller is able to meet the instructions of the PLC as when it is heating its internal heater just keeps ramping up constantly until it alarms and trips out the contactor. I have had an expert in to review the problem and he says it is not the PLC but the HMI controller on the heater unit itself but the problem is the company who made it have gone out of business so i cannot get help from them. The PLC guy did suggest putting in a controller with multi channel input so it can be regulated through the 3 different setpoints or possibly a second temperature controller. The HMI is turning on an output which is turning on a solid state relay which is then turning on the contactor which stays on until it trips because it doesnt know when to stop. I have attached photos of the back of the HMI controller along with the relays in use and the variable pots that are dictating the temperature, note that the unit alarms if i try adjust the pots, or even if i disconnect the output from the HMI, so it is like the relay banks (the Ascon Technologies ones from the photo) are constantly looking for a feedback loop, but i cannot be sure of this as i have no drawings at all. I am just looking for some direction as to where to go with this would a different controller help that could talk back to the PLC and do what i am looking for? Or is it a second probe, a signal isolator or what?054.jpg 055.jpg 056.jpg
 

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