Baxi Duo-tec Combi Boiler E119 Low Pressure Fault

Although I’m going to talk about a low-pressure problem if you have the Baxi Duo-tec Combi Boiler then well done as it was voted Boiler of the Year (gotta love that title) 2008 at the CORGI Awards.  The award is voted for by the people who work with it on a daily basis.  The boiler was also awarded a 'Best Buy' by Which? in 2007 achieving the top score.

E119 low pressure fault
Let’s get to the recent fault and I hope this helps someone.  We have had this boiler for 3 years and very occasionally in the past it has lost pressure and switches itself off displaying an E119 fault on the display.  Reading the user instructions this was easily solved by re-pressurising the system and something you can do yourself.

This picture shows the display and pressure dial on the boiler.  (Cam: C902)

Recently though the E119 fault is occurring with more frequency.  The constant loss of pressure would indicate a leak somewhere in the system. The leak is either going to originate in the boiler or in the pipework and radiators.

First job then is to switch the thermostat down low so it will not call for heating.  Re-pressurise the boiler to 1.5 bar and then turn off the flow and return valves under boiler. This then creates a break between the boiler and the rest of the system and allows you to problem solve.  Leave it an hour or two…… A pressure drop on the dial indicates a leak in boiler.  No pressure drop indicates a leak from somewhere else, ie the pipework or radiators. 

Where is the flow and return valves?
Look under the boiler front at the pipes from the boiler, the 2 large ones 22mm will be flow and return to your CH system. The 3rd large one in the middlish is the gas pipe. Looking at my picture below you can see the valve on each pipe, turn these to a horizontal position to isolate the boiler.

The flow and return valves under my boiler.  (Cam C902)

In my case the pressure continued to drop indicating the leak was on the side of the boiler. I had laid some kitchen roll under the boiler to identify any drips.  From this I could the see the connector that was leaking and which required a quick tighten. Once I was happy that the leak was fixed the flow and return valves could be turned back on and the thermostat raised so the heating kicks in. I was lucky this was an easy fix.

If there is no pressure drop on the boiler dial then it’s time to check pipe joins, the radiator taps, bleed screws and any other joins where there could be a leak.  The signs of water seepage should be easy to detect with a finger or piece of kitchen roll.  Once the leak is detected you can take whatever remedial action is required.

Here is a bit of info from the manual.
E119 is displayed when the primary water pressure is less than 0.5 bar. After re-pressurising the system the boiler should operate.  The normal operating water pressure is between 1 and 2.0 bar. If the pressure exceeds 3 bar the safety pressure valve will operate and a fault is indicated.

Re-pressurising the system
It may be necessary to re-pressurise the system occasionally. A filling device (the filling loop) will be fitted on the system. This will be on the boiler itself, or on pipe work near to the boiler.  If you are unsure of its position, or cannot identify it, consult the installer who fitted the boiler.
The filling loop consists of two taps and a separate copper pipe with connection fittings. Only when re-pressurising should the copper pipe be connected between the two taps. (Note – I keep mine attached all the time).

Here’s the filling loop in situ  (Cam: C902)

Fully open the tap while watching the pressure gauge, when the needle on the gauge is indicating 1 or more turn off the tap.  Disconnect the copper pipe from the taps (Note – as I say I keep mine attached) and remove it. Keep the pipe in a safe place for future use.

Good luck if your in the same situation.

A word about frequent depressurizing.  If you find no leaks anywhere  my guess would be that your expansion vessel has lost pressure. The expansion vessel, or expansion tank, is the small tank used in closed hot water heating systems that helps to absorb water pressure. If it's lost it's 'charge' then as your water heats up the pressure builds and because the expansion vessel isn't doing its job then the PRV kicks in to protect the system and this will give a E119 fault. Theoretically you can recharge the expansion vessel yourself , but this is a job best left for an engineer.