Short answer
Older Hamworthy boilers with Siemens LMU controls — Purewell VariHeat c and he, Fleet, Stratton mk1 and Wessex ModuMax mk2/HE — use their own fault list. The most common are 133 (no flame at end of safety time), 128 and 134 (flame lost during operation), 132 (safety shutdown), 110/111 (limit thermostat) and 118 (water pressure too low).
Lockout and internal codes
On LMU boilers a lockout code flashes with an alarm symbol (for example E150). Hamworthy's manual explains that pressing both line selection buttons for 3 seconds shows the internal error code (for example 238). Note both before resetting.
What usually causes them
These are older boilers, so worn flame probes, tired gas valves, perished seals and fouled heat exchangers are common. Code 129 (fan speed outside limits) often means a failing fan bearing. Repeated 133s on a cold morning are frequently low inlet pressure when the whole plant fires together.
Before you reset
A single reset after a power cut or a known one-off event is reasonable. Repeated resets are not: many commercial controls count resets and lock out further (for example a 'too many resets' code), and resetting a flame or gas valve fault over and over can mask a dangerous condition. If a lockout returns, isolate the appliance and call a Gas Safe registered engineer with the relevant commercial competence.
Hamworthy LMU control fault codes
| Code | Meaning | What to check |
|---|---|---|
| 10 | Fault outside sensor | Check connection, check sensor, check cable. |
| 28 | Fault flue gas sensor | Check connection, check sensor, check cable. |
| 32 | Fault flow temperature sensor 2 | Check connection, check sensor, check cable. |
| 50 | Fault DHW temperature sensor 1 | Check connection, check sensor, check cable. |
| 52 | Fault DHW temperature sensor 2 | Check connection, check sensor, check cable. |
| 61 | Fault room unit 1 | Check room device. |
| 62 | Wrong room unit 1 or wrong radio clock connected | Connect compatible room control unit. |
| 77 | Fault air pressure sensor | Check connection, check sensor, check cable. |
| 78 | Fault water pressure sensor | Check connection, check sensor, check cable. |
| 82 | Address collision on LPB | Check addresses of connected modules. |
| 91 | Data overflow in EEPROM | Hardware fault, LMU may need replacing. |
| 92 | Hardware fault in electronics | Hardware fault, LMU may need replacing. |
| 95 | Invalid time of day | Set correct time. |
| 100 | 2 clock time masters | Check settings of LMU, only 1 master allowed. |
| 105 | Maintenance message | P629 to reset : change from 0 to 1. |
| 110 | Limit thermostat has cut out | Allow the boiler to cool and reset thermostat, investigate cause of overheating. |
| 111 | Limit thermostat has cut out | Allow the boiler to cool and reset thermostat, investigate cause of overheating. |
| 113 | Flue gas supervision equipment has cut out | Check the cause of high flue gas temperature. Check sensor. |
| 117 | Water pressure too high | Check system pressure, check water pressure sensor |
| 118 | Water pressure too low | Check system pressure, check water pressure sensor |
| 119 | Water pressure switch has cut out | Check water pressure. |
| 128 | Loss of flame during operation | Check connections to flame probe. Investigate flame probe condition. Check combustion when boiler is firing. |
| 129 | Fan speed maximum/minimum has been violated | Check fan. |
| 130 | Flue gas limit temperature exceeded | Check the cause of high flue gas temperature. Check sensor. |
| 132 | Safety shutdown | Check gas pressure. Check flue & condensate trap for blockages. Check safety switches. |
| 133 | No flame on completion of safety time | Check operation of gas valve. Check spark igniter. |
| 134 | Loss of flame during operation | Check connections to flame probe. Investigate flame probe condition. Check combustion when boiler is firing. |
| 140 | Inadmissible LPB segment number/device N° | Check settings of LMU and boiler address settings. |
| 148 | Incompatibility LPB... interface / basic unit | Check settings of LMU |
| 151 | Internal fault with LMU | Check connections to clip in, replace module, check LMU. |
| 152 | Fault in connection with LMU settings | Check LMU settings. |
| 153 | LMU has locked out | Press reset button (code appears if reset button is pressed when there are no faults). |
| 154 | Flow Problems | Check water flow through the boiler & check the pumps. |
| 160 | Fan speed threshold not reached | Check obstructions in fan, burner & flue. Check non-return valve operates. Check heat exchanger for debris. |
| 161 | Maximum fan speed exceeded | Check parameters. |
| 162 | Fault air pressure switch (does not close) | Check air pressure switch and cable and connections. |
| 164 | Fault heating circuit flow switch / pressure switch | Check air pressure switch and cable and connections. |
| 166 | Fault air pressure switch (does not open) | Check air pressure switch and cable and connections. |
| 180 | Chimney sweep function active | Check boiler operation setting. |
| 181 | Controller stop function active | Check boiler operation setting. |
| 183 | LMU in parameter setting mode | Unit in programme mode. |
Source: Hamworthy Heating — fault code tool. Codes and meanings can differ between versions and control software — always check the manual for your exact appliance.
Figures are typical for UK natural gas. The current edition of the relevant IGEM standard and the manufacturer's instructions always take precedence on site.
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