Ferroli Modena 80 E: Pressure Leak

[Finhunter]

Hello all,

I have a Ferroli Modena 80 E Boiler that was fitted 13 years ago (approx). The boiler on the whole is still running well.

Last week I noticed that I have a slow pressure drop of around 0.5 bar over about a 9 hour period although I have noticed that the system pressure is not dropping any lower than about 0.9 bar.

From that I’m assuming that the leak I have is balancing out at about this pressure, 0.9 bar (although there may still be a sweat leak somewhere in the system).

I have bled the system and checked all the radiators and pipework that is above the floor level but can find no leak. So it looks as though my leak is below floor level.

My question comes in 2 parts;

• Would the use of Fernox F4 have a chance on sealing this leak (or is there a better sealer)? I know a repair of the leak is the best way to go but lifting laminate flooring at this time is not an option for me.

Whilst charging the stem to pressure the other day I inadvertently left the filling valve slightly cracked open which over pressurized the system then causing the safety valve to open to reduce the system pressure. There is now a very slow drip coming from this valve, mainly when the system is operating.

• Will I need to replace this? Will it gradually stop dripping? Can it be re-sealed?


Thanks in advance,


John

 

[MANDATE]

The PRV (pressure relief valve) opens at 3bar.
You have found one way of opening it. The other way is when the expansion vessel has lost some of it's air charge so when the heating is operating the normal rise in pressure of approx 1bar becomes considerably more.
However once opened a PRV seldom makes a good seal when closing again.
Your options are to either clean it or replace it with a new one, but do check the air pressure of the expansion vessel when there is no water pressure and open to atmosphere.
A expansion vessel should be around 0.8 to 1bar .
The system water pressure should ba approx 1bar cold and then rise when heating is on to approx 2bar.
If the pressure goes up near the 3bar mark, then the vessel has not been charged correctly or the diaphragm holed.

If you think the leak is on the system side and not the PRV, you can isolate the boiler with the flow and return valves. and observe the pressure gauge. If on the system side gauge pressure will remain stable. If on boiler side pressure will still drop.

 

[Finhunter]

Hi,

Thank you for the reply.

I should have added that I had tried closing both the flow/return valves for the CH system on Saturday with the pressure set at 1.5 bar and there was no drop after a 3.5 hour wait. So I assumed that the leak was definitively at the pipe/radiator side of the system.

The over-pressurizing of the system was an error on my part with the filling valve.

I have always ran the system at 1.5 bar so the sudden drop in pressure appears to be due to a new leak or associated problem.

Thanks again,

John