47 | P a g e
• Check expansion vessel not leaking, replace as required.
• If the expansion vessel is of adequate size for the property, is not leaking and has been fully
serviced but not holding pressure, replace the expansion vessel.
9. If no obvious leaks are found, isolate boiler from system and leave on test.
• *Note* system must be cold, and pressure set to approx. 1.5 bar before isolating valves from
boiler to system.
• The time required for this test will depend on patterns and amount of pressure loss. (i.e., every 2
days etc.).
109 Description: Constant filling, water pressure too high, > 3.0 bar
Cause: System water pressure higher than 3.0 bar.
1. Check filling loop is turned off and not passing, replace as required.
2. Check for secondary filling loops in the system and check as per point 1.
3. For combi’s check main water pressure not passing back through plate heat exchanger by isolating cold main
into boiler.
4. Ensure adequate expansion for property.
5. Check expansion vessel flexi hose is correctly connected with no kinks or blockages.
6. Check expansion vessel pressure is set correctly as per the manufacturer’s instructions, and check Shrader
core for leakage.
• Water in the expansion vessel may only be condensation and can be removed using the
expansion vessel service procedure found on page 68.
• Check expansion vessel not leaking, replace as required.
• If the expansion vessel is of adequate size for the property, is not leaking and has been fully
serviced but not holding pressure, replace the expansion vessel.
7. On rare occasions unvented cylinders may pass back to the central heating via a burst coil. Isolate the mains
to confirm.
110 Description: Flow sensor defective
Cause: The flow sensor T1 value out of range.
1. Check full T1 wiring harness and connectors for signs of damage, corrosion, or loose contact.
2. Use a multimeter to check T1 sensor resistances are in line with the return temperatures.
• The return temperature can be identified using the customer information menu.
• The resistances can be taken at the connector at the PCB (located on the bottom left of the
PCB next to resistor RL5, pins 3&4). This checks the wiring harness continuity at same time.
Disconnect the connector from PCB 1
st
to ensure no additional resistances are given through
the PCB.
• If the readings are incorrect, disconnect the wiring harness from the sensor and check the
sensor readings without the harness to prove if the sensor or harness is the fault.
Note thermistors may need cleaned and not always replaced.
3. If error 110 remains after the above has been checked, replace PCB.
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