Low Pressure in Ariston Microgenus 23 MFFI

[Daniel Bernard]

Hi All,

We have recently moved into a mid terrace 2 bed house with an Ariston Microgenus 23 MFFI boiler. Over the last few weeks, the pressure has dropped to pretty much zero (it may have been dropping gradually but I only noticed when the boiler kept needing to be restarted). I understand that I need to re-fill using the filling loop but when I compare my pipework to the boiler manual and other forum posts, there seems to be some additional parts. I have attached a picture but from my understanding (numbering relates to picture):

1 - This is the central heating intake valve/pipe. It has a blue tap
2 - This is a (subsequently fitted?) Myson combi loop linking the central heating intake and cold water mains
3 - This is, I think, the part of the combi loop stopping reverse flow?
4 - This is the cold water mains pipe/ It has a blue tap.

From what I have read, these boilers need to just have a filling loop pipe between 1 and 4. You then open both blue taps until the pressure is at the desired level. Currently though, there is no pipe between them and, when everything is open, water squirts out of both.

I had assumed that the Myson Combi loop had been installed further down to make it simpler and more accessible to fill the system but I can't find any combination of opening and closing 1,2,3 and 4 that results in the pressure going up. I either get nothing or water coming out of 1 and/or 4.

Any help would be greatly appreciated! I can provide more info if required.

Thanks in advance.

Dan

 

[denso13]

Are you opening 2 and 3? It looks like it may have a screwdriver slot on 3. Sometimes a new filling loop is subsequently fitted if there is an issue with the factory fitted one. That isn't unusual.

 

[Gasguru]

Yes not uncommon for the factory blue valves under the boiler to seize/leak/shear so close them up and ignore them.
The white Myson valve (with a combined double check valve) is well known for the spindle to seize up especially if appears to only open a turn or so.
With both the Myson and screwdriver slot valve off you could disconnect the loop and check for flow.

If you've only just moved into the property and the pressure has dropped so quick there's an issue with the boiler/system. What did the vendor say about the heating system on the tick box condition paperwork?

 

[ianmcd]

Valve 3 isnt a screwdriver slot, you will need a small adjustable or grips to open it, then use the white angled valve till at the correct pressure then close everything, you have a lot of build up on the isolating valve on the boiler, and fresh drips of water on a horizontal pipe these all need addressed

 

[Daniel Bernard]

Thanks for all your replies. I have closed both of the blue valves, opened up the white tap as far as it goes and then used a wrench to turn the spindle at #3 a long way in both directions and still can't hear any water, or see any change in the pressure gauge. I did manage to get some audible flow earlier in the day whilst doing this but I can't seem to get it going again. The spindle at #3 also seems to turn forever in either direction - it doesn't "lock out" no matter how far I turn either way.

with regards to the cause - The pressure has probably dropped as we have bled and removed some radiators to decorate behind etc as the heating system was working pretty well for the first month or so. We also had it safety checked which I appreciate probably wouldn't pick up these types of issues. The fresh drips on the pipework are from me trying out the various valves, not from any ongoing leak etc.

 

[ianmcd]

The spindle at #3 also seems to turn forever in either direction

The plastic head splines will have stripped, you will need to remove the head and use grips of some description

 

[ianmcd]

wrench to turn the spindle at #3 a long way in both directions and still can't hear any water,

you only turn it 1/4 turn, dont spin it round , the flats on the part you are turning indicate when it is open