fixmyplumbing

The customer is getting an E119 fault everyday. They top up the pressure in the morning and it’s gone by the afternoon.

This is a classic expansion vessel fault.

The expansion vessel is a tank with an air bubble inside. (Red tank on the left). It uses this air bubble to keep the pressure in the system steady.

Over time (or if there is a fault) the air bubble leaks away and pressure in the system is no longer controlled.

When the system heats up the pressure isn’t controlled so goes too high. It is then released by the safety valve. This lowers the pressure causing the E119 fault.

The air bubble is reinstated in the tank using a bike pump.

When the bubble is back in the expansion vessel the pressure should stay under 2.5bar when hot.

Modern boilers are designed to be safe. All the dangerous bits are sealed up inside an air tight case. This means if anything does go wrong inside the boiler the carbon monoxide doesn’t tend to leak out into your house.

It also means that if things are going wrong you may not know about it until it’s gone very wrong.

This boiler I serviced was a potterton promax combi (a very good boiler incidentally). The customer was happy with how it was working, never had to reset it, all working very well.

When I took the cover off the marks of leaking heat and fumes were obvious immediately. The rubber sealing gasket for the burner had disintegrated and was no longer sealing the heat exchanger.

Along the top edge of the burner door you can see wispy white marks where the fumes and heat have been leaking. In the bottom of the case was white powder from the metals corroding. When I took the burner out it was obvious that the silicone rubber seal had failed.

Luckily this had been caught in time at the yearly service so no harm had been done.

The new silicone rubber seal costs a few quid. Fitting it takes hardly any time and because it’s in the middle of a service all the safety checks have to be done anyway so no extra work.

I’ve come across this seal failing a few times. Mostly caught early. Two were not caught early.

The first one had the fumes and hot gasses leaking for a long time which burned through the wiring and spark generator above the heat exchanger. This eventually put the boiler off. A costly job replacing the parts.

The second one was left for even longer. It eventually melted the wiring , spark generator and burnt though the plastic body of the main heat exchanger. Parts cost went into the hundreds and labour added even more hundreds.

The moral of the story is that a stitch in time saves nine. Get your boiler checked once a year. It might save you a lot of money and trouble.