Leaking Megaflow Cylinder

[twgas]

No, before anyone mentions it , I'm not G3.

But the installation was done originally by a G3 bloke who notified the council etc, yet he had failed to install an important safety device, so as far as I am concerned, after rectifying the installation and adding an additional vessel plus pressure gauge, I have only made it somewhat safer than the original certificated install.

Am I missing something, but I can't see where you've said what safety device the G3 fitted omitted.

 

[Axel]

When I moved into the house, there was no pressure relief valve on the megaflo, the one that's part of the combination valve. Only the T & P was there.

 

[twgas]

If the safety device you say he left off is part of the combination valve, did he remove it and plug the hole?

 

[DP]

A megaflo's operating pressure is 3 bar.

Axel, your understanding of expansion vessel is flawed as is knowledge of safety components on unvented cylinders.

 

[Axel]

The pressure reducing valve is set to limit the pressure presented to the cylinder from the mains pressure in if it exceeds 3bar. Mine doesn't ever rise above 2 bar, but if Thames Water start to supply over 3 bar then the pressure REDUCING valve will limit it to 3 bar.

Of course, once the water heats up and expands, the pressure inside the megaflo will increase, but the expansion allowed by the compressible air bubble in the megaflo or in an external expansion vessel will absorb this expansion and the pressure in the cylinder won't rise much at all.

The other valves - the pressure / expansion relief valve and the temperature and pressure valve are only to open if there is a problem with the expansion vessel or the air bubble in a Megaflo, but these will only open if the pressure rises to 8 bar or whatever it is, I still refuse to go downstairs and look in the cupboard for the precise values.

If you wish to criticise my knowledge, then kindly explain where I have mis-understood the concepts etc.

 

[Axel]

If the safety device you say he left off is part of the combination valve, did he remove it and plug the hole?

There was a plugged outlet on the 3 bar pressure reducing valve, yes.

 

[DP]

1. I fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)

Axel, If I supplied you a red expansion vessel with a charge pressure of 8 bar, would you fit that to the UV cylinder. It is after all a high pressure expansion vessel.

fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)

Would you fit such a vessel on the outlet side or the inlet side?

 

[twgas]

There was a plugged outlet on the 3 bar pressure reducing valve, yes.

Are you sure this wasn't the balanced cold supply connection?

 

[DP]

There was a plugged outlet on the 3 bar pressure reducing valve, yes.

Pressure reducing valve for mark 3 has three ports. These are inlet (marked with an arrow pointing into the body of the valve) an outlet with arrow indicating flow out of the valve. These two ports are in line. Third port is at right angle to afore mentioned ports. Is this the port that is plugged up (if memory serves me right, it comes plugged up)?

 

[Axel]

1. I fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)

Axel, If I supplied you a red expansion vessel with a charge pressure of 8 bar, would you fit that to the UV cylinder. It is after all a high pressure expansion vessel.

fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)

Would you fit such a vessel on the outlet side or the inlet side?

No, I wouldn't fit a red expansion vessel to an UV cylinder, as I have already stated. And I would not be charging any vessel to 8 bar. The charge pressure I have set on my additional vessel is 2.8 Bar at the moment. 8 bar is the limit the emergency valve will open at. It is not relevant to the normal correct functioning of the cylinder.

Additional vessel is connected to the inlet side after the PRV etc just before cylinder along with a gauge.

 

[Axel]

There was a plugged outlet on the 3 bar pressure reducing valve, yes.

Are you sure this wasn't the balanced cold supply connection?

No, that was yet another blanked connection.

 

[Axel]

There was a plugged outlet on the 3 bar pressure reducing valve, yes.

It was a while ago I replaced the old Pressure reducing valve (which had a leak) and that was when I noticed that the correct replacement part was a combination valve that included the expansion relief valve as well as the pressure reducing valve with check valve, strainer etc.

As I have it now, the cold mains goes into the arrow on the pressure reducing valve and then out the opposite side directly into the expansion relief valve. The other port on the pressure reducing valve is blanked off as there is no pipework previously installed to provide a balanced cold supply.

The expansion relief valve has it's output to the cylinder inlet, with a separate outlet going to the tun-dish. There is also one more connection on it to which I have connected an expansion vessel and a gauge, and the whole system works very successfully.

 

[DP]

Axel, what confuses me is your statement below

I fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)

What I am saying is I can supply a red high pressure expansion vessel.

 

[kevplumb]

i think he means potable dan

we all know the pressure is somewhat unimportant

 

[DP]

Kevin, that was the bit I was looking for. Nothing to do with high pressure vessels. Use of red vessel is a common error I come across regulalry