Sinclair SCV-EB Series Service Manual page 72

Broken expansion vessel
The water flow rate is not sufficient,
caused by crushed or bent water piping,
high resistance in water piping
Replace hydro system PCB
Notes:
1. Inlet water temperature sensor (Tw_in) connection, outlet water temperature sensor (Tw_out) connection is port CN6 on the hydro system PCB.
2. Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor's resistance
characteristics table, the sensor has failed.
70
No
No
Make sure the expansion vessel is not
Yes
Ensure maximum system head is
Yes
within pump head and flow rate range
broken.