Relay Logic 2nd Opinion

We have a line that has a PLC on it, the panel is out of room, the rack is out of slots, and the PLC is out of inputs. I am looking at a manual mode to make the line run backwards.

Right now, the PLC runs the line automaticaly forward. The system uses solenoids to raise sections of the drive belt to run against the bottoms of the rollers. I will be using a switch to run a relay, and that relay will disable the motor in the forward direction, as well as turn on a second relay the 2nd relay will then engage the motor in reverse, as well as manually connect 110vac L1 to the solenoids I need to drive. Should I use the NC contacts on the #1 relay to disconnect the solenoids from the PLC, or since they are using the same L1 leg, I shouldnt be out of phase, so it wouldnt matter.

Should I use the NC contacts on the #1 relay to disconnect the solenoids from the PLC? or since they are using the same L1 leg, I shouldnt be out of phase, so it wouldnt matter.

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Somehow you need to fix your circuit to disable the PLC control while it is on. I would use the new switch (2 poles) to disable the PLC Solenoid OUTPUTS at the same time. If this switch is ON, the PLC cannot energize the solenoids. You may have to add a master control relay to part of the PLC output power supply, if you don't have one already. Sooner or later, someone will move the solenoids to a different leg of the panel, maybe after you are retired or laid off.

The reason is simple.

If there are two or more ways of doing something and one of those ways leads to a disaster (turning on both Forward & Reverse controls at the same time), then someone will do it. - Edward A Murphy's Law

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