Low Water Pressure Insufficient water pressure and consequent intervention of the minimum water pressure switch ( 13 )
The 08 error code on Unical boilers indicates low water pressure insufficient water pressure and consequent intervention of the minimum water pressure switch ( 13 ).
Unical 08 means: low water pressure insufficient water pressure and consequent intervention of the minimum water pressure switch ( 13 ). On this component the documented failure modes are system water pressure too low, or a leak somewhere in the system. You can safely reset the boiler once — if 08 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does 08 Mean
The 08 code is shown by the boiler’s control board when it detects low water pressure insufficient water pressure and consequent intervention of the minimum water pressure switch ( 13 ). The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 08 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 5 different manufacturers.
| Cause |
|---|
| System water pressure too low, or a leak somewhere in the system |
Safety Warning
08 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
How to Fix It
Repressurise the system to the pressure stated on the boiler — typically 1.0–1.5 bar (15–22 psi) when cold. If it drops again, look for a leak on pipework, radiator valves and the pressure relief discharge.
Refer to the Unical service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Unical models that can display fault code 08:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Unical models | — | Possible |
Frequently Asked Questions
Repressurise the system to the pressure stated on the boiler — typically 1.0–1.5 bar (15–22 psi) when cold. If it drops again, look for a leak on pipework, radiator valves and the pressure relief discharge. According to the technical documentation, this is the first check on the list for 08.
08 is not classified as a high-severity fault, so the boiler can be reset once. If 08 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.