On the display
The message on the display reads SYS X LOW SUCTION SUPERHEAT. The manual's fault tables print it as SYS X YYYYYYYY LOW SUCTION SUPERHEAT: X is the number of the system that tripped, and the YYYYYYYY field between the system number and the message text indicates a FAULT condition or a LOCKOUT.
What it means
This is the Low Suction Superheat Cutout Fault, one of the system safeties. It helps protect the compressor from liquid floodback due to low suction superheat. The response is a controlled ramped shutdown of the system. The safety is ignored for the first 30 seconds of compressor operation.
Why it appears
- After the first 30 seconds of run time, with discharge superheat below 15°F and run time below 5 minutes: if suction superheat falls below 2.0°F, the safety is ignored for the next 30 seconds, then the cutout is set to 0°F and ramps linearly to 2.0°F over the next 60 seconds — the fault trips if suction superheat falls below the ramped cutout during those 60 seconds.
- Suction superheat stays below 2°F while discharge superheat is below 15°F for 10 seconds, with run time of 5 minutes or more.
- Suction superheat stays below 0.5°F while discharge superheat is above 15°F for 60 seconds, with run time of 5 minutes or more.
- Suction superheat stays below 5°F for 10 minutes.
Setpoints and thresholds
- Safety ignored for the first 30 seconds of compressor operation.
- Ramped cutout (run time below 5 minutes, discharge superheat below 15°F): cutout starts at 0°F and ramps linearly to 2.0°F over 60 seconds.
- 10-second trip: suction superheat below 2°F, discharge superheat below 15°F.
- 60-second trip: suction superheat below 0.5°F, discharge superheat above 15°F.
- Sustained trip: suction superheat below 5°F for 10 minutes.
- The 10-second and 60-second trips require run time of 5 minutes or more.
- Restart delay: 120-second anti-recycle timer.
- Lockout: 3 faults on the same system within 90 minutes.
Reset and restart
The system restarts automatically after the 120-second anti-recycle timer times out. It locks out after 3 faults on the same system within 90 minutes — if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad
. The manuals describe clearing the lockout by cycling the system switch OFF and ON.
Questions engineers ask
What does SYS X LOW SUCTION SUPERHEAT mean on a YORK YCAV?
It is the Low Suction Superheat Cutout Fault: a controlled ramped shutdown that helps protect the compressor from liquid floodback when suction superheat drops too low. X is the number of the affected system, and the status field shows FAULT or LOCKOUT.
Will a YORK YCAV restart on its own after a low suction superheat fault?
Yes. The system restarts automatically once the 120-second anti-recycle timer times out, unless the fault has escalated to a lockout.
How do I clear a LOCKOUT after low suction superheat on a YCAV?
A lockout follows 3 faults on the same system within 90 minutes, and the system will not restart until the operator clears the fault using the keypad. The manuals also describe clearing the lockout by cycling the system switch OFF and ON.
What suction superheat values trip the YCAV low suction superheat safety?
After the first 30 seconds of operation: below 2.0°F against a ramped cutout (with discharge superheat below 15°F), below 2°F for 10 seconds, below 0.5°F for 60 seconds, or below 5°F for 10 minutes. The 10-second and 60-second trips apply once run time is 5 minutes or more.
Messages next to this one
Source
Written from the manufacturer's manuals for the YORK YCAV; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YCAV messages: fault codes · YORK YCAV documentation · YORK manuals