Potterton [E119] fault codewhat it means and how to fix it

E119 is low system pressure, and on a Potterton it is worth thinking about slightly differently from the same code on a newer appliance. Most Promax boilers in service are now on the far side of fifteen years, attached to pipework and radiators that are older still. On a system of that age the question is rarely whether there is a leak somewhere but where, and how much corrosion the repeated refilling has already caused. Every time fresh mains water goes into a sealed system it brings dissolved oxygen with it, and that oxygen attacks steel radiators and produces the black magnetite sludge that eventually blocks heat exchangers and seizes pumps. A Promax that needs topping up monthly is not primarily a pressure problem; it is a system being slowly destroyed by the remedy. That is the argument for finding the leak rather than living with the routine, even though topping up is quicker and free.

1. 1

   Open the drop-down flap on the front of the Promax to see the display and the reset button. A surprising number of these appliances are reported dead when the flap has simply never been opened.

2. 2

   Find the pressure gauge. On most Promax installations it is a separate round gauge on the pipework beneath the appliance rather than on the front panel.

3. 3

   Locate the filling loop — usually a braided silver hose between two pipes below the boiler, with a small lever valve at each end.

4. 4

   Open both levers slowly until the gauge reads 1.2 bar cold, then close them firmly. Check they are properly shut by feeling whether the hose is still cold and quiet.

   Do not fill beyond 2.5 bar cold. On an older system, over-pressurising can start a leak at a joint that was previously holding perfectly well.
5. 5

   Hold reset for five seconds. Then walk round every radiator and feel underneath each valve for damp — with the system freshly pressurised, a weep is easier to find than at any other time.