SLC Card Fault

Hey guys,
So recently my iO panel started giving me a communcations fault trouble for all my devices. Not good! I’m using 22/2 solid wire for the communications path even though the recommended is 18/2. Could that cause a problem? Also I have some devices running into a cold environment, but I doubt that would kill the whole circuit?

Hopefully it’s just a wiring problem as a new SLC card would be expensive!

Try to isolate the problem, disconnect the SLC and use some spare wire and hook up a device to the SLC and see if it responds.

The panel was giving an SLC fault. The cause, short. I found a wire possibly being crushed so I moved it out of obstruction, and so far it’s behaving. I’ll let you know if anything changes.

22/2 solid is very thin and it’s quite possible that some of the data is getting lost between your panel and the devices, and while that isn’t your problem right now, you won’t be able make very long wire runs with 22/2 before you start getting random communication troubles. Most manuals include a wiring diagram that lists the minimum wire type and thickness next to the maximum length it can run from the panel and still carry good data.

Also, with wire that thin, especially if it’s unshielded, cross-talk can be an issue. If any of the wire is hung next to a high voltage AC connection (like the cord feeding the panel), or even higher-current DC circuits (like a 24V NAC), they can induce small voltage spikes/currents in your SLC. While all systems have safeguards that prevent these extraneous voltages from causing any damage to your panel, depending on how much cross-talk happens, the panel can start reading bad data and get confused by signals it’s receiving on the line, resulting in random SLC errors (think “Missing,” “Invalid Reply,” “Wrong Type,” or even Ground Fault).

TL;DR: for the short runs you’re doing, it’s probably just fine, but if you need to make longer runs consider some thicker gauge wire.