Boiler Pressure Droping

[JamesRees05]

Hi
I ve had problems with my ferroli combi boiler(11 years old )on and off for the last 6 months. The pressure keep s dropping. I definitely have no leaks. I ve had the PRV replaced and the expansion vessel replaced. And still it is dropping.

When I had the expansion vessel done, it was ok for 3 weeks. Pressure did nt move at all. But after 3 weeks it was has if the problem as come back again.

I'm losing a 1 bar every 3-4 weeks.

Any suggestions what else this could be ?

Regards

 

[bengasman]

...The pressure keep s dropping. I definitely have no leaks...

Yes, you do. Dropping pressure = leak.

 

[martyndc88]

exp vssle may not be charged correctly

 

[Jake1886]

You got any htg pipes laid in screeded floors?

 

[45yearsagasman]

You must check the basics first before diving in. Check the vessels precharge as mentioned earlier and also the connecting pipe. Then check the relief valve is not passing. If they all prove correct then you may well have a leak.
Strange that it was ok for a while?

 

[Gasman77]

Small leak on heat ex, being evaporated by the heat of the burner would be my guess young man

 

[MANDATE]

Don't overlook the Scharder valve on the expansion vessel. The vessel may have been charged to the correct pressure, but the slightest air leak will allow the air pressure to drop. Too low a pre charge means the volume of air in vessel is reduced. A smaller volume of air when compressed means higher pressures attained so prv opens. PRVs once opened rarely close correctly due to dirt on sealing valve face.
If you observe water pressure when heating is switched on, what pressure does it increase to? and from what initial pressure

 

[JamesRees05]

I have no pipework going under the floors, its all on show. I ve looked round all the system and tightened up all the fittings.

For example the pressure when off is 1.5 bar, then when turned on it rises to 1.7-1.8 bar .

I'm no plumber but I have a gut feeling that its something on the boiler not the system.

Also when I turn the hot water tap on fully for the bath, the boiler only pumps hot water for about 20 seconds then the water goes Luke warm. But when I only open the tap half way its fine, it can cope with that.

I want to claim on my house insurance for a new boiler but I ve gotta feeling they ll tell me to bog off cause it s still in working order, any ideas ?

 

[Gasman77]

You must do the most basic test you can do first - isolate the boiler from the rest of the system for 24/48 hours and not use it. You will at leats know if it a boiler or system fault.

Had this before on untraceable leaks, like I said, small leak on the heat ex evaporating

 

[gblades]

No idea about the layout inside your boiler but in mine I have had the automatic air vent leak in the past. It was dripping down and collecting on a plate next to the burner chamber so got evaporated off when the boiler came on. Only noticed it when it got worse enough to leave a small pool of water under the boiler overnight.