YORK YCAV — UNIT VSD CT PLUG FAULT

The panel reads UNIT VSD CT PLUG FAULT. The manual records this safety as item 18 in its list of unit VSD faults and classifies it as a unit fault for all units, so it is announced at unit level rather than for a single circuit. The manuals group it under the VSD safeties (faults).

This is a hardware-generated VSD fault raised by the VSD Logic Board. Each CT plug on that board has a jumper installed in it, and those jumpers feed back signals telling the board whether the plugs are installed. If either plug is not installed, the board reads a low value on its digital input. The response is immediate: a running unit shuts down on the fault at once, and a unit that is off is inhibited from starting.

• A CT plug is not installed on the VSD Logic Board. With the plug missing, the jumper that should feed back the “plug installed” signal is out of the circuit, so the board reads a low value on its digital input.

1. Check that each CT plug is installed on the VSD Logic Board. The jumper inside each plug is what feeds the “plug installed” signal back to the board.
2. Check both plugs, not just one: the manual states the fault occurs if either plug is not installed, so a single missing plug is enough to trip the fault.
3. If a plug is found uninstalled, fitting it back restores the jumper feedback and removes the low value the board reads on its digital input.

• Auto-restart: the unit restarts after the 120-second anti-recycle timer times out.
• Lockout threshold: the unit locks out on the 3rd fault in 90 minutes.

The manuals treat this as an auto-restart safety. After a shutdown the unit restarts by itself once the 120-second anti-recycle timer has timed out — no action at the keypad is needed for that restart. If the fault occurs a 3rd time in 90 minutes, the unit locks out instead, and a lockout will not restart until the operator clears the fault using the keypad.