Pressurised system problem

Bannman · 24 Nov 2007

To move two upstairs radiators I drained the central heating system. Moved the radiators and started to refill the system, as I refilled the system building up the pressure and bleeding radiators the pressure release valve for the central heating system (not the valve on the pressure vessel) started allowing water out of the system and flooding my garage. Consequently I could not build up the pressure on the system. I was told that this due to an airlock in the system and that the water could not push it too the radiators.

I stopped trying to fill the system and cleaned up the mess!! To try and get the pressure up in the system I took off the pressure release valve for the central heating system and fitted a valve which allowed me to seal the system, I then repeated the process building up the pressure and bleeding radiators. Eventually no more air came out of the radiators and the pressure remained at 1 bar.

Can I switch on the heating system with valve that is sealing the system closed or could this allow too much pressure to build up in the system? If so could this pressure not be released through the pressure release valve on the pressure vessel?

Need some advice what to do next.

Thanks in advance

chrishutt · 24 Nov 2007

The PRV is a vital safety device and you mustn't use the system without it. However it should not release water until a pressure of 3 bar is reached. If yours is releasing water at much lower pressures then it needs replacing, although I have to say that is very unusual - I suspect you have left it in the open position. Try twisting the red knob so that the valve closes.

gas4you · 24 Nov 2007

Agree with Chris. But let it 'bang' shut rather than release it slowly.

Bannman · 24 Nov 2007

When the water was flowing out of the pressure release valve in the garage the gauge on the pressure vessel (in the attic) was reading around 1 bar and continually dropping, due to the relaese of water

The valve that allowed water to flow out is next to the air vent for the central heating system.

I originally had a normal heating system and recently got it pressurised the pressure valve that is allowing water out was part of the old systyem, it is basically a spring loaded valve.

chrishutt · 24 Nov 2007

In that case you can leave it off, providing the system has a proper PRV valve fitted near the boiler. Incidentally which boiler do you have?

baxpoti · 24 Nov 2007

How high is the attic from the garage (roughly in meters)?

Bannman · 25 Nov 2007

baxpoti said:
How high is the attic from the garage (roughly in meters)?

I have a two storey house with a converted attic. The attic is roughly 6m above the garage.

Does anyone know why the PRV in the garage "blew out" when the pressure reading on the gauge on the pressure vessel only read 1 bar?

If there is air in the system could I turn on the pump (without the boiler)to try and move the air to the top radiator?

Bannman · 25 Nov 2007

chrishutt said:
In that case you can leave it off, providing the system has a proper PRV valve fitted near the boiler. Incidentally which boiler do you have?

Truco Trojan

chrishutt · 25 Nov 2007

Bannman said:
Does anyone know why the PRV in the garage "blew out" when the pressure reading on the gauge on the pressure vessel only read 1 bar?

The old open system had a static head of 0.6 bar (6 metres), so the old safety valve would have been set to open at a slightly higher pressure, so 1 bar (10 metres) sounds about right. It's also likely that the safety valve was scaled up and may not have opened at 1 bar before, but when you refilled the pressure shock may have freed it.

No trace of Truco Trojan on the net. What type of boiler is it (oil, gas, how old)?

Bannman · 25 Nov 2007

chrishutt said:
Bannman said:

Does anyone know why the PRV in the garage "blew out" when the pressure reading on the gauge on the pressure vessel only read 1 bar?

Click to expand...

The old open system had a static head of 0.6 bar (6 metres), so the old safety valve would have been set to open at a slightly higher pressure, so 1 bar (10 metres) sounds about right. It's also likely that the safety valve was scaled up and may not have opened at 1 bar before, but when you refilled the pressure shock may have freed it.

No trace of Truco Trojan on the net. What type of boiler is it (oil, gas, how old)?

Have checked the PRV and it has scaled-up also held it under the tap in the kitchen and water dripped out. It would seem that this valve is not sealing properly.

The boiler has Truco Trojan written on it and the burner is a Sterling 40 burner

bengasman · 25 Nov 2007

You have a pressure gauge, but does it also have a red knob that lets water out when you turn it? if so, is this water safely let out to the outside of the house? Both are pretty essential.

Bannman · 25 Nov 2007

bengasman said:
You have a pressure gauge, but does it also have a red knob that lets water out when you turn it? if so, is this water safely let out to the outside of the house? Both are pretty essential.

The pressure vessel (in the atic) has a knob that lets water out. The PRV that is giving me the bother was one beside the boiler (in the garage), I think it is to ensure that too much pressure does not build up in the boiler.

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Pressurised system problem

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