System pressure high ( 2.9 bar, 42.1 psi)
The E117 error code on Potterton boilers indicates system pressure high ( 2.9 bar, 42.1 psi).
Potterton E117 means: system pressure high ( 2.9 bar, 42.1 psi). 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 E117 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E117 Mean
The E117 code is shown by the boiler’s control board when it detects system pressure high ( 2.9 bar, 42.1 psi). 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 E117 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
E117 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.
Step-by-Step Diagnosis
1. Check the boiler pressure gauge — normal operating pressure is 1.0-1.5 bar (15–22 psi) when cold. 2. Inspect all visible pipework, radiators, and valves for signs of leakage. 3. Check the pressure relief valve discharge pipe — if water is dripping, the PRV may be faulty or the expansion vessel has failed. 4. Test the expansion vessel — with the system cold and drained, check the Schrader valve on the vessel
air should escape at the correct pre-charge pressure (typically 0.75-1.0 bar, 11–15 psi). 5. Inspect the pressure sensor connections. 6. Check automatic air vents for signs of weeping
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 Potterton service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Potterton models that can display fault code E117:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Potterton 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 E117.
E117 is not classified as a high-severity fault, so the boiler can be reset once. If E117 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.