On the display
The panel reads UNIT FAULT: PUMP FAIL MAKE FLOW. This is the only wording the manual prints for the message. The unit has locked out and the running pump has been stopped.
What it means
This is Unit Fault Code 28, Pump Flow Failure, on Hydro Pumps 1 or Hydro Pumps 2. After the 30-second stop-to-start timer the control starts a pump — when the Leaving Liquid Temperature Cutout is active, when any compressor is running, or when the daily schedule is not calling for shutdown with the unit switch ON and the remote stop/start input closed. The message means that pump started but the flow switch did not close within 10 seconds, so flow was never proven and the unit locked out.
Why it appears
- The pump was started but the flow switch did not close within 10 seconds of the start.
- On units with two pumps, duty and standby: the running pump failed to close the flow switch within 10 seconds and was stopped, the standby pump was started, and it too failed to close the flow switch within a further 10 seconds.
- A tripped manual motor starter on one of the pumps — the manual calls for these starters to be checked when attempting to clear this fault.
What to check
- Check that one of the manual motor starters protecting the pumps has not tripped.
- Reset the trip (unit switch OFF, then back to ON) and watch the restart: the pump starts after the 30-second stop-to-start timer and the flow switch must close within 10 seconds.
- On dual-pump (duty and standby) units, remember the standby pump is started automatically if the first pump does not make flow within 10 seconds; the lockout occurs only if the flow switch is still open after a further 10 seconds.
Setpoints and thresholds
- Unit Fault Code 28 — Pump Flow Failure (Hydro Pumps 1 or Hydro Pumps 2).
- Pump stop-to-start timer: 30 seconds.
- Flow switch must close within 10 seconds of the pump starting.
- Dual-pump units: a further 10 seconds after the standby pump starts.
- Lockout on the first fault (1x).
Reset and restart
Setting the unit switch to OFF, then back to ON resets the trip
. The unit locks out on the first fault (1x), so this reset is required every time the message appears. Before resetting, check that none of the manual motor starters protecting the pumps has tripped.
Questions engineers ask
What does UNIT FAULT: PUMP FAIL MAKE FLOW mean on a YORK YLAA?
It is Unit Fault Code 28, Pump Flow Failure, on Hydro Pumps 1 or Hydro Pumps 2. The pump was started but the flow switch did not close within 10 seconds, so the unit locked out and stopped the running pump.
How do I reset PUMP FAIL MAKE FLOW on a YLAA?
Set the unit switch to OFF and then back to ON. The unit locks out on the first fault (1x), so the reset is needed each time the message appears — and first confirm that no manual motor starter protecting the pumps has tripped.
Why does my YLAA trip on PUMP FAIL MAKE FLOW?
Because the flow switch did not close within 10 seconds of the pump starting, which follows the 30-second stop-to-start timer. On dual-pump duty and standby units, the standby pump also gets 10 seconds before the unit locks out.
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