Temperature relief valve dripping

[Matt0029]

On an unvented cylinder if the expansion vessel has lost its charge. Can this still be the cause of dripping/discharge from the temperature relief valve. Or if the expansion had lost its charge would it discharge through the pressure relief on the composite valve? Thanks

 

[SJB060685]

If the expansion vessel had lost its charge I'd expect the expansion relief valve to act first, unless itself was faulty. If the combined temperature and pressure relief is discharging that symbolises other problems. Either can be affected by a number of things. If you're not G3 then best get someone who is to attend.

 

[king of pipes]

Clue is in the question Matt it will be one or the other temperature or pressure or possibly both or a fault with the valve G3 mate ? . Kop

 

[Matt0029]

I am g3 yes. I've had it before were the pressure relief on the composite valve has dripped as the expansion has vessel has lost it charge. The expansion has lost it charge its charge on this one. The temperature relief has its own tundish on it and is dripping I cant tell if the pressure relief is dripping too as its combined after the tundish.

 

[SJB060685]

Is there anyway you can catch the drip from combined temperature and pressure relief and check pipe termination for possible expansion relief drip? Having said that that is installed wrong and both need to terminate into D1 of tundish.

 

[Matt0029]

Is there anyway you can catch the drip from combined temperature and pressure relief and check pipe termination for possible expansion relief drip? Having said that that is installed wrong and both need to terminate into D1 of tundish.

Yes I release it is installed wrong. I will recharge the expansion vessel before I go any further.

 

[EvilDrPorkChop]

Failed expansion or in need of a recharge yes the combined Temperature/Pressure relief will drip

 

[Matt0029]

Failed expansion or in need of a recharge yes the combined Temperature/Pressure relief will drip

Thanks so the pressure relief on the composite valve and the temperature relief would drip. I can only confirm the temperature relief is dripping presently due to the position of the tundish.

 

[SJB060685]

If the vessel had lost its charge, too much charge or failed altogether, or the pressure reducing valve had failed or not present then the expansion relief valve SHOULD drip first as its pressure setting is usually 1 bar lower than the combined pressure and temperature relief valve. The only time I would expect the combined pressure and temperature relief valve to activate due to excess pressure is if there's a problem with one of the above and the expansion relief valve had failed.

Edit: If there was a problem with a mixer unit letting by then any cold mains pressure not balanced and at higher pressure than supply to cylinder can also cause this problem.

 

[Ben-gee]

If one uses the balanced supply and there is a problem meaning the valve to the unvented needs to be shut off - the property loses all water. Is this a usual scenario?

 

[EvilDrPorkChop]

If the vessel had lost its charge, too much charge or failed altogether, or the pressure reducing valve had failed or not present then the expansion relief valve SHOULD drip first as its pressure setting is usually 1 bar lower than the combined pressure and temperature relief valve. The only time I would expect the combined pressure and temperature relief valve to activate due to excess pressure is if there's a problem with one of the above and the expansion relief valve had failed.

Edit: If there was a problem with a mixer unit letting by then any cold mains pressure not balanced and at higher pressure than supply to cylinder can also cause this problem.

In my experience the T&P always drips when expansion has failed. Agreed in theory the PRV at 6/7 should activate first, however from what I have seen they don’t. You also have to remember the T&P only start dripping, not discharging. They can start dripping at 6/7 bar before their set point.

 

[Matt0029]

If one uses the balanced supply and there is a problem meaning the valve to the unvented needs to be shut off - the property loses all water. Is this a usual scenario?

The one I'm looking at just has the balanced cold caped on the composite valve. I'm not sure if there's another pressure reducing valve on the mains. So back pressure could be an issue too I guess.

 

[John.g]

A pressure gauge, if fitted, should give a good indication of what's happening, it should also rise and fall with the cylinder heating/cooling.