We have a 2 year old Baxi Maxflow Combi WM (gas-fired, room sealed powered flue combi boiler which incorporates a 54 litre unvented hot water storage cylinder) which has been making making loud banging noises (thump. thump, thump) for the past couple of months.
When pump operates for the first time for the central heating circuit it makes this loud banging sound for a second or two. ie Central heating timer starts central heating mode - water heats up to required temperature (no noises) - once pump starts to pump the water around the radiators you get the thump, thump, thump but only at the start. If you use hot water during a central heating period, cylinder refiils, water heats up to required temp and central heating circuit restarts with a thump, thump, thump. Thats the only time we hear that banging sound (again only at the start).
Central Heating Pressure Gauge on the combi shows the pressure is/was okay (in the green). I've bled the radiators of air but only recently did it for the first time a short while back when the noises started
. Repeated the bleeding again (quite a lot of air this time and refilled system). Noise quietened down for a day or so then returned.
Here is more info on the boiler if it is of any help
Quoting from the manual
"If there is a call for central heating the diverter valve operates and the pump circulates the primary heating water, operating the differential pressure switch. The fan will run at full speed; once the air pressure switch has been proved the burner will light. The burner output then automatically adjusts to suit the system demand; as the temperature of the heating water in the boiler approaches that set by the adjustable central heating control knob the burner output is reduced. When this set temperature is reached, the burner extinguishes and the fan stops. The pump continues to run for 3 minutes to prevent residual heat build up in the boiler. The burner will not relight for 3 minutes unless there is a demand for domestic hot water during this period."
Any ideas? Air trapped? Faullty automatic air vent?
When pump operates for the first time for the central heating circuit it makes this loud banging sound for a second or two. ie Central heating timer starts central heating mode - water heats up to required temperature (no noises) - once pump starts to pump the water around the radiators you get the thump, thump, thump but only at the start. If you use hot water during a central heating period, cylinder refiils, water heats up to required temp and central heating circuit restarts with a thump, thump, thump. Thats the only time we hear that banging sound (again only at the start).
Central Heating Pressure Gauge on the combi shows the pressure is/was okay (in the green). I've bled the radiators of air but only recently did it for the first time a short while back when the noises started
. Repeated the bleeding again (quite a lot of air this time and refilled system). Noise quietened down for a day or so then returned.Here is more info on the boiler if it is of any help
Quoting from the manual
"If there is a call for central heating the diverter valve operates and the pump circulates the primary heating water, operating the differential pressure switch. The fan will run at full speed; once the air pressure switch has been proved the burner will light. The burner output then automatically adjusts to suit the system demand; as the temperature of the heating water in the boiler approaches that set by the adjustable central heating control knob the burner output is reduced. When this set temperature is reached, the burner extinguishes and the fan stops. The pump continues to run for 3 minutes to prevent residual heat build up in the boiler. The burner will not relight for 3 minutes unless there is a demand for domestic hot water during this period."
Any ideas? Air trapped? Faullty automatic air vent?
