heatrae sadia megaflow

[susan saunders]

I have a megaflow system which is giving so much hassle. I have had two plumbers and a further recommended one by Heatrae Sadia. It has been serviced back in february. every four months the overflow runs in through the tundish. each plumber has replaced the pressure valve, and at more or less four months, I get water running again. it is quite a lot, I have to put a basin underneath and mop up with towels. the water pressure has been checked and is below 8 bar which is the limit for the proper heatrae part. I have been throwing money at it for a long time now and getting nowhere. please, can someone suggest something?

 

[Steelmasons]

External expansion vessel is required.
High water temperatures will deplete the internal bubble (air gap) in a short space of time.

 

[hertsboilers]

It is a common failure by their internal air gap, and has nothing to do with PRV or TPRV, the pressure relief valves.

I am surprised that the company still products cylinders with this failed design.

 

[Agile]

Guy I have been working with has to reform his every month!

But it is a user task which any competent user can do.

It even gives the instructions on the side!

If you have to mop up water it sounds as if its not installed correctly!

Tony

 

[dilalio]

+1 For external vessel.
The expansion of the heated water is not being absorbed by the internal diaphragm of the 'bubble'.
This could be due to a number of things... More expansion than it is designed to cope with; air depletion and/or faulty schrader valve; defective/split diaphragm.
The only route that the expanded water can then take is through the PRV to discharge.
As Agile said... You shouldn't have to "mop up"! Where is water spilling from? Tundish? This would suggest restriction downstream of tundish and that would mean scalding water backup!

 

[picasso]

Could also be mains passing back into the hot water system, the next time it happens turn off the supply to the cylinder (not the supply to the rest of the house) and wait ten minutes, if the water is still running through the tundish or at any hot tap you have found the problem.

 

[susan saunders]

thanks so much for all your advice. I have regenerated the airgap and it makes no difference. it is the first thing the plumbers try as well. the mopping appears to be due to the quantity of water coming through, it splashes around the tundish and spills over. I know what will happen, the plumber will come back with yet another pressure valve, which will look as though it has fixed it, and then 4 months later we are back to square one!

 

[susan saunders]

can anyone recommend a better unvented system? we need pressure because it is situated at the bottom of the house with a lot of bathrooms to supply. a different manufacturer? it is quite old, was here when we moved into the house and I keep reading that they are not very good.

 

[Agile]

Where is this "pressure valve"?

Is it the pressure and temperature valve towards the top of the cylinder?

It sounds to me as if the pressure reducing valve is at fault. This is mounted near to the cylinder on the pipework. They are quite expensive too, close to £100.

Or as suggested a cross leak somewhere else in the house such as a shower mixer valve.

Tony

 

[Steelmasons]

+1 For external vessel.
The expansion of the heated water is not being absorbed by the internal diaphragm of the 'bubble'.
This could be due to a number of things... More expansion than it is designed to cope with; air depletion and/or faulty schrader valve; defective/split diaphragm.
The only route that the expanded water can then take is through the PRV to discharge.
As Agile said... You shouldn't have to "mop up"! Where is water spilling from? Tundish? This would suggest restriction downstream of tundish and that would mean scalding water backup!

No diaphragm or schrader on the megaflo in question , more often than not the internal disc (flying saucer) has flipped upon itself.

 

[Steelmasons]

The only way to generate "air bubble" is to completely drain the cylinder of all water......set cylinder stat to 65c which will maintain air gap for a longer period of time....setting higher than 65c will deplete bubble at a faster rate.