Hi,
Sealed system, direct feed, Ideal Standard NF60 boiler, Megaflo water heater
Had a faulty 2 port valve (micro switch not working properly) and leaking PRV on cold water mains feed. Both were replaced professionally. System was drained down to below water heater level to carry out the work.
Since the work has been completed, I cannot regulate the pressure on the boiler. I understand it should be at around 1-1.25 bar. Normally, it would commonly lose 0.5 bar during 6 months and I would re-fill through filling loop.
Now when boiler is heating water for central heating, the pressure continues to rise (unless the thermostat kicks in, which has been tested) and eventually will rise above 3 bar. I assume the pressure relief valve opens at this point.
However, the water will discharge from the discharge pipe thereafter, when running at a much lower pressure, and the system pressure will reduce. Engineer checked expansion vessel, which contains air and has not failed, which has about 0.8 bar pressure.
I can understand some water and pressure loss if PRV has opened and not sealed properly and needs to be replaced. However, why is the system rising to 3 bar in the first instance and surely this will only open a replacement PRV?
Further, the water coming down the discharge pipe is cold. It does not originate from the water heater as I have checked the tundish and it is not flowing through this, so must be sourced from the boiler PRV, but how can it be cold? I am sure it is central heating water as it has a bluish colour which I assume is the inhibitor that was added.
The pressure drops after one heating cycle (an evening) to about 0.5 bar and needs to be topped up constantly.
One further point, when the system was not topped up, when the hot water was next being heated, there was a lot of 'air' running in the system and the hot water taps expel this (quite a lot of it) when opened.
Gas engineer is looking to replace PRV on boiler, but I'm not sure what is causing the high pressure in the first instance given the expansion vessel is ok. I can confirm filling loop is closed and not leaking (as otherwise pressure would rise when not in use). Any help would be much appreciated.
Sealed system, direct feed, Ideal Standard NF60 boiler, Megaflo water heater
Had a faulty 2 port valve (micro switch not working properly) and leaking PRV on cold water mains feed. Both were replaced professionally. System was drained down to below water heater level to carry out the work.
Since the work has been completed, I cannot regulate the pressure on the boiler. I understand it should be at around 1-1.25 bar. Normally, it would commonly lose 0.5 bar during 6 months and I would re-fill through filling loop.
Now when boiler is heating water for central heating, the pressure continues to rise (unless the thermostat kicks in, which has been tested) and eventually will rise above 3 bar. I assume the pressure relief valve opens at this point.
However, the water will discharge from the discharge pipe thereafter, when running at a much lower pressure, and the system pressure will reduce. Engineer checked expansion vessel, which contains air and has not failed, which has about 0.8 bar pressure.
I can understand some water and pressure loss if PRV has opened and not sealed properly and needs to be replaced. However, why is the system rising to 3 bar in the first instance and surely this will only open a replacement PRV?
Further, the water coming down the discharge pipe is cold. It does not originate from the water heater as I have checked the tundish and it is not flowing through this, so must be sourced from the boiler PRV, but how can it be cold? I am sure it is central heating water as it has a bluish colour which I assume is the inhibitor that was added.
The pressure drops after one heating cycle (an evening) to about 0.5 bar and needs to be topped up constantly.
One further point, when the system was not topped up, when the hot water was next being heated, there was a lot of 'air' running in the system and the hot water taps expel this (quite a lot of it) when opened.
Gas engineer is looking to replace PRV on boiler, but I'm not sure what is causing the high pressure in the first instance given the expansion vessel is ok. I can confirm filling loop is closed and not leaking (as otherwise pressure would rise when not in use). Any help would be much appreciated.
