Our Vaillant VCW242 has suddenly developed a problem where it cannot heat up the hot water sufficiently. It normally produces hot water (I don't know the temperature but it's too hot to touch probably 60-65C) at about 9 litres/min. This morning I had to reduce the flow at the tap to 3 litres/min to get hot water at the same temperature, so running a bath takes ages and the shower is useless.
The boiler is probably well over 15 years old (we've been in the house 9 years) and I've replaced a lot of the 'water' side components: diverter valve, diaphragm, heat exchanger, extraction fan etc. and I'd noticed that the boiler would fire up with a lowish flame and then flare up (i.e. gas flow increase) after 5 seconds or so. Now it all fires up ok but it doesn't seem to have the increase in gas flow, so the burners are not supplying as much heat per unit time as they were yesterday (about 1/3 in fact). I am guessing that there is a mechanism that checks something (perhaps water flow or pressure) before telling the regulator to increase the gas flow to maximum.
Assuming my guess is correct, then the fault would be in the sensor, the control circuitry or the gas regulator. The probability of an electronic failure with no other symptoms is low. If the fault is on the gas side it is beyond my ability to safely repair but it would be useful to have other input.
Does anybody have any ideas or has anyone seen these symptoms before?
The boiler is probably well over 15 years old (we've been in the house 9 years) and I've replaced a lot of the 'water' side components: diverter valve, diaphragm, heat exchanger, extraction fan etc. and I'd noticed that the boiler would fire up with a lowish flame and then flare up (i.e. gas flow increase) after 5 seconds or so. Now it all fires up ok but it doesn't seem to have the increase in gas flow, so the burners are not supplying as much heat per unit time as they were yesterday (about 1/3 in fact). I am guessing that there is a mechanism that checks something (perhaps water flow or pressure) before telling the regulator to increase the gas flow to maximum.
Assuming my guess is correct, then the fault would be in the sensor, the control circuitry or the gas regulator. The probability of an electronic failure with no other symptoms is low. If the fault is on the gas side it is beyond my ability to safely repair but it would be useful to have other input.
Does anybody have any ideas or has anyone seen these symptoms before?