Biasi RIVA COMPACT HE MK2, pressure loss-not usual suspects!

[MrBenjamas]

Hi all

I'm a bit lost with my boiler at home. its a Biasi RIVA COMPACT HE MK2, model number M96A.24SM/C GC number 47-583-17.

Now follows a long tale, but hopefully i'll cover everything and someone may have some ideas on what to try next as I'm a stuck.

We moved here a few years ago, and the boiler was already installed, there was no paperwork with it at all.

Its always worked fine until last year when it started losing pressure. it was blowing out the safety valve. I got my uncle to come tack a look as he is gas safe qualified plumber, but he's near retirement now and needs help labouring, so we worked on it together.

We changed the valve and things improved until a few months ago, the pressure would rise a lot and then blow out around 3 bar as I would expect.

I did some research and read the service manual and deduced it was possibly a expansion vessel problem, so i drained it down and tested the pressure in the expansion vessel with the heating system fully drained.

sure enough there was no pressure in there, but also no water. I re pressureised it with a foot pump to 1 bar and refilled the system. it was good for a bout a week before the same problem returned.

I drained it down again and tested the expansion vessel, it was empty again and this time had a little moisture at the valve.

I called my uncle in and we then bought a new expansion vessel and another new safety valve and fitted these. Then all seemed good, when running flat out the system pressure would barely rise more than 1/4 - 1/2 a bar, so it seemed to be finally sorted.

now its losing pressure again, I'm confident it is not out of the safety valve, the joints where we fitted the new expansion vessel all seem dry and fine. when running, the boiler still barely rises in pressure so I'm happy the vessel seems to be doing it's job and I cant see any leaks in the house anywhere.

The only place thats been disturbed in the last 18 months is under the bathroom floor, where we had a new rad fitted. its a tiled floor over boards so I'm loathe to pull it up to check but am concious this could be a culprit. We have no visible leaks on the ceiling below though.

So I'm wondering is there anything else we can check?

if there was some residualy air left in the system that I hadnt been able to bleed out of a rad, how long would it take to make it's own way out of the auto bleed valve near the pump? could this account for about 1/2 bar loss in a week?

I'm thinking the worst at the moment that theres a crack or soemthing in one of the exhangers

Thanks in advance for any help

Ben

 

[MrBenjamas]

Little update (and shameless bump)

I let the boiler cool right down this morning and then shut off the CH circuit flow and return then left for work for the day.

The idea being if there was a leak during the day, then I would get a pressure drop as I opened the valves this evening. I've just completed this and noted no drop, no noises at all.

So unless theres a fitting that leaks only when warm, then I'm fairly sure there are no leaks on the system. Is this a fair assumption?

 

[Agile]

You cannot make any assumptions!

Best to rise pressure to about 2.0 bar and boiler cold to look for leaks.

Have you felt round ALL the rad valves and looked on your hand for moisture?

The condensate output pipe needs to be checked. ( Unlikely but a professional has to consider all eventualities.)

If nothing found then open if you dare and remove the diverter valve motor and see if the bottom part is wet!

Many, many, other possibilities though!

Tony

 

[MrBenjamas]

Thanks for replying Tony.

I've checked the diverter motor, the manual refers to it as the electric actuator, I presume it's the same thing? Iremoved it and saw the pin. There is no moisture present there or inside where it contacts the valve.

What checks should I perform on the condensate pipe?

I'll do a cold 2.0 bar test on Friday when I can leave it all day to see if it drops.

Is there anything else I can try? Could the diverter valve be leaking into the DHW ?

Thanks

Ben

 

[Agile]

You need to see if water comes out of the condensate drain when the boiler is not in use!

Tony

 

[MrBenjamas]

Thanks Tony, i checked and it seemed fine.

a little update, I ran the heating up to full power and opened all the rad valves fully including all the thermostatic valves. (I guess I should have done this already). Anyway when I bled the top most radiator I got a little rasping water out of it.

It seems to have been fine ever since.

I can only imagine I still had a lot of air in the system, some must have been making it's way out of the auto purge valve in the boiler which was dropping the pressure. Anyway so far so good, hopefully i wont be back in a weeks time saying it's dropped again.

thanks for the help.