Ariston Microgenus 23

[hopelessjohn]

Hi I have the above boiler and the pressure in it keeps rising to around 3.5 bar when it vents from the overflow. At this point I have to drain the system using a drain off valve on a radiator downstairs until the pressure is reduced to around .5 - 1 bar.

I've been trying to work out whats happening and from reading on here it seems likely that it is either the heat exchanger or the refilling loop that is at fault. If I understand correctly, the filling loop is the flexible pipe that runs between inlet and outlet pipes and should be removed after filling. Mine, however has always been attached since I moved into the house about 3 years ago. I've discovered that if I turn off the water into the boiler, the pressure doesn't rise but then I have no water from hot taps. Does this confirm the heat exchanger is the problem or have I totally misunderstood everything??

Please excuse me if any of this is stupid, I have no idea what I'm doing here, I'm just trying to work it out!

Any help gratefully received.

John

 

[EliteHeat]

I've discovered that if I turn off the water into the boiler, the pressure doesn't rise but then I have no water from hot taps. Does this confirm the heat exchanger is the problem or have I totally misunderstood everything??

That would seem to indicate a perforated plate heat exchanger - so you're not so hopeless after all John

 

[Agile]

You have probably understood the situation!

You should disconnect the filling loop to ensure its not letting by. If it still rises with the filling loop off then its the heat exchanger leaking from the secondary to the primary side.

Tony

 

[hopelessjohn]

Thanks for the quick replies!

Because the filling loop has always been connected I was concerned that it might leak if I disconnected it! I'll go and have another look in a minute and see if I'm brave enough to unscrew things...

Any guesses as to the cost of having the heat exchanger replaced? I've seen that a replacement part is likely to cost around £140 and I'm wondering how much the labour might/should be.

Thanks again for your help.

 

[Rob]

Aslong as either both the black taps or Blue knobs are closed there shouldnt be much water if it is letting by. This is more likely than the Heat Exchanger.

 

[bengasman]

If the filling loop is letting by, it can easily be replaced. Simple job and not expensive.
If you leave the filling loop as is and the pressure stops rising when you shut off the inlet to the boiler, it is pretty sure that your plate exchanger is gone. Not a common fault on a microgenus though as far as I am aware.
Did you turn the water of at the inletvalve on the boiler or with a separate valve before the boiler?

 

[hopelessjohn]

i used a separate inline valve before the boiler - is that ok?

 

[Agile]

Its a question of whether the isolator you turned left the filling loop still pressurised or if it cut the supply to that as well.

I dont see why you dont want to remove the filling hose. Even if the valve was leaking they are cheap and easy to replace.

Its about two hours work to replace a main HE and about one hour to replace a plate. Both times including a service/performance test.

Tony

 

[hopelessjohn]

it's not so much that I don't want to, more that I'm not sure how to and I'm concerned that it might start pouring out water if I disconnect it! I think I'm going to get British Gas to try and fix it by taking out one of their monthly payment arrangements...