Boiler - Pressure Drops

[PaulG]

Firstly, I know there are loads of posts about similar problems, but none fit my boiler's symptoms exactly...

I have a Ferroli Optima Combi Boiler, in which the pressure drops. For example, when the central heating is on, the pressure will be about 1.5 bar say (it sometimes rises slightly when the heating is on). When the heating is then turned off, the pressure drops down to 0. Also, if the hot water is turned on for any period of time whilst the heating is also on, the pressure will drop down to zero.

I have checked the overflow pipe that runs to the outside of the building, and there is a constant drip when the heating is on. From other posts, I'm assuming there is a problem with the Pressure Release Valve but I don't know how to confirm this.

I've already been stung by an Engineer who said it was probably the Expansion Vessel, but that it probably just needed re-pressurised. He duly did this, and needless to say I was back to square one after a day. When I called him back, he suggested the Expansion Vessel may need replaced. Does it sound like a problem with the Expansion Vessel, or with the PRV?

Before I call out an another Engineer, I'd appreciate if anyone could offer advice on the likely cause.

 

[Paul Barker]

If your pressure guage is working then it isn't likely to be the expansion vessel. Also when he pumped it up he would know then if it is patent and would have told you at the time you needed a new one. To be certain you just let pressure out of water side, depress needle in midle of bike pump valve if water comes out you need a new vessel if air you don't. Check pressure with pressure guage, should be about 1 bar. Pump up with bike pump if not.

You main problem is pressure relief valve. Buy another for about a fiver, drain down heating system, fit the plastic parts only it's much easier and all that's required. Nopw refill the system, to a pressure of 1 to 1.5 bar when cold.

Your problems should now be over.

 

[meldrew's_mate]

Actually this sounds EXACTLY like lots of other posts where the conclusion is that your expansion vessel has probably failed.

I sounds like your previous fitter gave you reasonably good advice, as for stinging you make your own mind up!

 

[Paul Barker]

If the expansion vessel had failed the pressure would rise to 3 bar, 1.5 bar is the pressure reported. Either my chrystal ball is failing or the ev is working. In any event I have explained in simple terms how to check it, when we visit an appliance we prove everything regardles of history because people forget our chrystal balls are cloudy.