need unvented advice

[Billy Bob Bob]

not had my g3 ticket for a while so not working on unvented that often anyway i look after a old retired gas engineer poor sod us in 30 years, multiple health issues and asbestosis too boot,anyway he respects me enough to sort his issues out this guy was the kiddy in his day and has passed me loads of work,his unvented cylinder has a 3 bar prv on the cold main its fitted with a 6 bar safety valve thats passing,now he only has 3 bar coming in on his main so why has his safety valve failed? its a range tribune cylinder no external expansion vessel visable now does this cylinder have a internal expansion vessel and could this cause the safety valve on the cold main to fail? i am assuming its there to stop the cylinder being over pressured,the higher up safety valve bolted to the cylinders fine not passing at all

 

[shaky]

We look after some flats on a HA that have theses cylinders fitted and as far as I'm aware there is no internal e/v in them and were are for ever replacing T&P valves on them.

 

[Paulplumb]

Fitted one of the tributes and the vessel is contained under the lid of the un vented cylinder. This is a direct cylinder? Pop the lid off the top and check that the bladder in the pressure vessel hasn't failed.

 

[Billy Bob Bob]

Fitted one of the tributes and the vessel is contained under the lid of the un vented cylinder. This is a direct cylinder? Pop the lid off the top and check that the bladder in the pressure vessel hasn't failed.

its indirect

 

[Paulplumb]

May be the seat of the valve has just perished. You had a peek?

 

[AWheating]

is it an air pocket? maybe needs to be drained and refilled?

 

[Billy Bob Bob]

May be the seat of the valve has just perished. You had a peek?

could not get the pipework apart bar tight wanted to check the outlet

 

[Billy Bob Bob]

is it an air pocket? maybe needs to be drained and refilled?

my thoughts also but why would the safety valve on the cold main fail but the cylinder ones ok?

 

[chris watkins]

my thoughts also but why would the safety valve on the cold main fail but the cylinder ones ok?

T&P is always set at a higher pressure than the expansion relief. (if it's 6 bar TRP likely to be 8)

 

[Paulplumb]

The one that goes into the side of the cylinder is a temperature relief valve.

 

[chris watkins]

The one that goes into the side of the cylinder is a temperature relief valve.

temperature & pressure it is combined.

 

[vern]

Mark sort ASAP sould have an external expansion vessel, 6 bar valve blowing on expansion, these had flexi hose in to side of valve that has failed, other end of flexi to vessel how long has it been like that?

 

[Paulplumb]

Regenerate the air gap as Mr Wheating suggests, sorry missed that bit out. Too many Cuba libres ;-)

 

[vern]

Regenerate the air gap as Mr Wheating suggests, sorry missed that bit out. Too many Cuba libres ;-)

No air gap, external vessel on these, sized acorrding to cylinder capacity in litres

 

[mfgs]

The tribunes have an external vessel like has been said.

 

[Billy Bob Bob]

Mark sort ASAP sould have an external expansion vessel, 6 bar valve blowing on expansion, these had flexi hose in to side of valve that has failed, other end of flexi to vessel how long has it been like that?

not sure vern old guy had noticed it ages ago according to him,its dribbling into a drain,no flexy fitted its strait off the 22mm cold feed after the prv

 

[Megaflo-Experts]

Is the pressure relief passing continuously, or only when the water is being heated up?

If continuously, then it's likely to be the pressure relief valve or the pressure reducing valve (assuming the incoming mains pressure is greater than 6 bar).
If only when heating up, then probably due to expansion which would be the case if there was no expansion vessel. But, this would have happened from day one, unless something changed recently.

 

[vern]

not sure vern old guy had noticed it ages ago according to him,its dribbling into a drain,no flexy fitted its strait off the 22mm cold feed after the prv

So deffo no expansion vessel?

 

[Billy Bob Bob]

So deffo no expansion vessel?

no external one anywhere fits been in about 10 years

 

[Billy Bob Bob]

Is the pressure relief passing continuously, or only when the water is being heated up?

If continuously, then it's likely to be the pressure relief valve or the pressure reducing valve (assuming the incoming mains pressure is greater than 6 bar).
If only when heating up, then probably due to expansion which would be the case if there was no expansion vessel. But, this would have happened from day one, unless something changed recently.

continually dripping cold main pressures low 3 bar

 

[vern]

no external one anywhere fits been in about 10 years

Sweet Jesus get one fitted asap, and replace the inlet valve set, it will need a slight repipe as the control sets have changed 3 times since then, nowt hard though

 

[Megaflo-Experts]

continually dripping cold main pressures low 3 bar

I would say the pressure relief valve is faulty and need replacing.

 

[vern]

I would say the pressure relief valve is faulty and need replacing.

Thats on the inlet valve set, now combined not separate, vessel on asap!!!

 

[Megaflo-Experts]

Thats on the inlet valve set, now combined not separate, vessel on asap!!!

If it's combined, then yes agree with Vern.

 

[vern]

Mark....expansion trust me work on these weekly........vessel on and water inlet control set, job, done.....hows its run for 10 years i have no idea, get me some pics for a laugh:grin: