MAIN CONDENCING BOILER FAULT Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[shawplumb]

MY MAIN BOILER FAULT LIGHT HAS STARTED FLASHING, AFTER RESETTING I NOTICE IT THAT WHEN THE HEATING WAS ON AND THE HOT TAP WAS OPENED THE HEATING PRESSURE JUMPS UP BAR 0.5 BAR AND THE FAULT LIGHT FLASHES .WHEN THE TAP IS CLOSED THE PRESSURE DROPS BACK TO NORMAL. CAN ANYBODY THROW ANY LIGHT ON THIS ?

[htg engineer]

What model is the boiler ?

The boiler pressure should be above 0.5, try re-pressurising the system it could be that the sytem pressure is too low.

[DONFRAMAC]

It looks as though there is some gas in the radiator loop, which will respond by showing extra pressure, when the DHW is operating, as it shuts off the rads. pump, so the fluids in the rads. system will occupy more volume, until the DHW use stops.
I would shut-down the boiler, and air-bleed the rads., then top-up the boiler pressure, using the filling loop, to 1.5 bar, then re-start the boiler on DHW+rads.
It is likely that only one or two rads. will have had some gas content.
(I say gas as water corrosion in radiators creats hydrogen, and topping-up water holds some dissolved air, but the oxygen disappears by creating solid magnetite particles, rusting the rads.)