On the display
The message is printed exactly as System Fault; this is the only spelling the manual lists for it. It is one of the fault/inhibit code names of this chiller, defined in the data map as: Fault/inhibit code name in the Native BACnet, Modbus, and N2 communications data map (reported via the Sys 1 / Sys 2 Fault Code points)
. The code is therefore reported separately for system 1 and system 2, and a controller reading those points over the communications link sees the same name the panel shows. The entry defines the name only — the manual attaches no cause and no corrective-action text to this code name.
What it means
The manual separates two levels of fault response: the unit is shut down on a unit fault, or locked out on a system fault — the respective contacts will open when the unit is shut down on a unit fault, or locked out on a system fault
. A system fault is thus a lockout condition, and System Fault is the name the control reports for it.
The lockout is visible at the terminal block. The normally-open alarm contacts open whenever the unit shuts down on a unit fault, locks out on a system fault, or experiences a loss of power to the chiller electronics. System 1 alarm contacts are located at XTBC2 Terminals 29 to 30, and system 2 alarm contacts at XTBC2 Terminals 31 to 32. The contacts close again when conditions allow the unit to operate or the fault is reset; after a loss of power they remain open until power is reapplied and no fault conditions exist.
The fault also holds the unit off: before the start sequence can run, all run permissive inputs must be satisfied and no chiller or system faults may exist, so a daily schedule start or a remote cycling device cannot bring the unit in while this condition is present.
What to check
- Identify which system reports the code: it is carried on separate system 1 and system 2 fault code points, so check which of the two points is set.
- Verify the state at the alarm contacts: XTBC2 Terminals 29 to 30 (system 1) and Terminals 31 to 32 (system 2). Open contacts mean the unit is shut down on a unit fault, locked out on a system fault, or without power to the chiller electronics; the contacts close again when conditions allow the unit to operate or the fault is reset.
Questions engineers ask
What does System Fault mean on a YORK YLAA chiller?
It is the fault/inhibit code name reported through the Native BACnet, Modbus, and N2 communications data map on the system 1 / system 2 fault code points. It corresponds to a lockout condition, which the manual distinguishes from the shutdown caused by a unit fault.
How can I tell which system is locked out?
The code is reported via separate system 1 and system 2 fault code points, and each system has its own normally-open alarm contacts: XTBC2 Terminals 29 to 30 for system 1 and Terminals 31 to 32 for system 2.
Will the YLAA restart while System Fault is active?
No. The start sequence requires that all run permissive inputs are satisfied and no chiller or system faults exist, so the unit stays off until the fault condition is cleared and the fault is reset.
Messages next to this one
Source
Written from the manufacturer's manuals for the YORK YLAA; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YLAA messages: fault codes · YORK YLAA documentation · YORK manuals