Oso unvented cylinder problem

[fedupwithheating]

Please Please Please can someone help me.

Been living in a new build house for past 4 years and having problems with my hot water supply/ central heating since the day we moved in.

The 5 bed house runs off a Oso condensing cylinder. Approx every 4-5 months there is a surge in pressure to the hot water taps followed by a few radiators springing leaks. I've been told time and time again that they run independant of each other and not to confuse the two. So why do they always go hand in hand?

I am not technically minded but have built up a good awareness of this system over the past 4 years. I understand the reason for the surge in hot water pressure is due to the air-pocket in the cylinder being replaced by water. This is also confirmed by the fact that water ommits from the tundish when the surge in water starts up, and remains until the plumber has re-charged the air-bubble again.

Attempts to remedy the problems have been:-

replace separate pressure gauge
replace separate expansion vessel
upgrade water meter from 15mm to 22mm
check stop-cock opened fully
replace showers as possibly faulty valves allowing water back into the system
all olives and joints to radiators replaced incase poorly made-up or overtightened!?!
can't remember the figures but supposedly there is also good water pressure/ supply to the property

The guy from Oso himself has even been to visit me and suggests the problem lies with the mains pipework. The majority to the property is 32mm but where it is connected to the water meter, a small part of it reduces to 15mm. Great - just get the water company to increase the size of the pipework? Not so - this is standard on all the meters, and unfortunately I seem to be the only one on this 70 house development with problems to the hot water supply. Having said that, I know numerous neighbours who have leaking radiators but some are just living with it by putting bowls underneath to catch the drips!

Is there anyone out there who can throw any more light on the situation or advise an alternative 'good' and 'easily maintainable' unvented cylinder?

I will be your best friend for life if you can help!

 

[mario500]

Oso cylinders are quite good. Maybe your Ch system has a problem with corrosion? Do you have to bleed rad on a regular basis?

The surge in domestic hot water in unrelated to the radiator problems.

Maybe your expansion vessel is undersized or maybe the diapram inside is damaged. The expansion vessel comes as part of the oso kit so probably not undersized.

Did the oso engineer pick up on any faults with the installation?

AL

 

[fedupwithheating]

Hi mario500,

The Oso rep found no faults at all with the installation, however, his comments were to check 2 possible faulty shower valves (which have since been changed), the reduction in the pipe to 15mm where the water meter has been attached, and thirdly, he recommended fitting an additional expansion vessel to extend the time period that the cylinder is needing the air-bubble recharged. We have not actioned this as we are wanting to find out the cause of why it needs re-charging so often - delaying the time is just eating into my warranty with the builder and not actually solving the problem.

The rads do not need bleeding at all but have been checked.

With regard to corrosion, the water runs quite clear from the rads (when they have been made-back up after leaking). The inhibitor has also been checked to see at the correct level - it is. Also as the house is only 4 years old, I've been told that there shouldn't be any corrosion - Does this sound right to you?

Finally, the expansion vessel. There is a separate orange expansion vessel attached to this Oso system. Again, for fear the internal flange had a hole or tear, this has also been replaced for new. The Oso guy said the air-pocket on the Oso cylinder was internal and did not have a flange, so no fear of ripping/ tearing - it's just a cylinder part filled with water/air. Eventually air absorbs water and therefore as part of your yearly maintenance it should be drained off - however, as I've said, mine is requiring the water to be drained every 4-5 months.

Hope the above provides you with a bit more insight. I welcome any further questions/ comments. Thanks so far!

 

[wattcom]

Hi I have the same issue did the second expansion vessel cure the problem

Sick of recharging the tank every 4/6 months

 

[kevindgas]

fitted a few of these so have an idea of them and how they work.

1 the air bubble is created by a tube that is fitted in the top of the cylinder. a drain down to Temp/ pressure relief valve level will recharge it
2 the filling loop must have 2 stop taps and a non return valve and should be removed when not in use.
3 the filling loop should ideally be fitted after the pressure reducing valve
4 the pressure reducing valve should be checked with a pressure gauge connect it to filling loop if fitted as 3 above should be 2 - 2.5 bar

these are normally very reliable and only need an annual service.

 

[Norcon]

Do the shower valves have a balanced feed for the cold inlet and not taken direct from mains?

 

[fedupwithheating]

Hi Folks,

Sorry I haven't looked at this for a while. Thanks for your input so far.

Since I last wrote, my Oso condensing cylinder was changed for a new but bigger Oso condensing cylinder. But after 5 months, we are back to square one. The last plumber appointed by the builder doesn't have a clue, and his response was to re-charge the air-bubble yet again!!!

I have now been appointed another plumber from a different firm. He rang Oso technical department as he wanted to check whether a certain component should be there (sorry for my lack of knowledge - I just keep picking up bits and pieces as I go along). It had something to do with the flow and return. Oso advised that an external one wasn't required as it was built-in to their cylinder. So the plumber cut a joint out and replaced it with just standard copper piping. In addition to this, he states that the cold and hot water supplies were being fed upstairs at different rates. He added/changed a pressure reducing valve and when finished said they were now both running at 30 whatevers a minute (or second - I can't remember)!!!

This work was only carried out last week, so only time will tell. But to wattcom, I hope it doesn't take you as long as it has me to figure all this out. If you are in a New-Build and are still under warranty, all I can suggest is that you email or write to the builder each time (rather than phone), that way if the problem is still ongoing after your standard warranty ends, NHBC will back you up if you have written proof it is the same problem from day 1 that has never been fixed.

Thank you to kevindgas and Norcon. If the problem persists, I will pass your info onto the assigned plumber.

Many Thanks

fedupwithheating