FNL_ENG (Customer) asked a question.
I have a P1-M401-16DR with 8 AC/DC inputs and 8 relay outputs. each set of 8 has a single common identified as C1 and C2. The documentation isn't clear (to me) that C1 and C2 must be of the same polarity. My project is using 24VAC. I wired it up so that I supply 24VAC hot to my input devices and when true they send 24VAC hot to the input terminals. I connected the 24VAC Neutral wire to C1. I wired my output devices so that they require a 24VAC hot to be delivered from the output terminals when switched on. 24VAC Neutral is connected to the other side of my output devices(motor starter for example). I connected 24VAC hot to terminal C2. When I switched on power, my 24VAC circuit breaker tripped. If I remove either C1 or C2, the breaker doesn't trip. C1 and C2 must be connected internally. The documentation doesn't tell me that they are, or that I must connect the same signal or polarity to C1 and C2. The documentation on page 5 of the user guide that comes with the hardware looks very much like I can connect anything I want to C1 or C2. I would expect that I could connect DC com to C1 and DC+ to C2, or an AC source to one and DC to the other, etc. I think it would be good for the documentation to point out that they must be of the same type and polarity, or otherwise indicate that they are connected.
I reached out to our supplier, and they confirmed that C1 and C2 are not internally connected on the P1-M401-16DR. C1 serves as the common for the input circuits, while C2 supplies the common side of the relay output contacts.
Since the breaker only trips when both commons are tied together, this points to an unintended path somewhere in the external wiring or through one of the connected field devices.
Could you send us a complete wiring diagram showing the 24 VAC power source, input devices, output loads, and all connections to the P1-M401-16DR? That will help us pinpoint where the hot-to-neutral path is occurring.