Sudden leak in boiler and heating system!

[Corazones]

I wonder if anyone can suggest the reason for my boiler problem, as the only engineer who knows the system well has just gone on holiday for a month!

I have a Grant Vortex Eco condensing wall-hung oil boiler in a sealed system, which heats rads, underfloor and hot water. Last week the boiler appeared to be running continuously all day, though the noise was more like the start-up routine than full ignition - but I could be mistaken, as the flow pipe seemed very hot. Then it stopped working.

The problem which stopped it was a blown O-ring in the underfloor control valve, causing a loss of fluid and pressure. The valve was replaced, the system refilled and checked, and the boiler started as normal.

A day later I noticed a leak below the boiler. I turned everything off and it stopped. I also noticed the system pressure had fallen 0.5 bar, so it seemed unlikely to be a condensate leakage.

A further day later and the boiler leak has returned, even though it's off. It seems to be from the left side, where the heat exchanger etc is, although I can't see anything as it's all covered in foil and insulation.

Could something have occurred which caused both the O-ring and the heat exchanger gasket to burst? Surely there are too many safety devices to prevent anything like that, and the boiler's only 4 years old.

What to do now? I am thinking of calling Grant's own engineer out on the basis that he'll carry all spares with him - would that make sense, or be unnecessarily expensive?

Many thanks for your advice,
Alec.

 

[Corazones]

I found someone local who has taken a look, and I think he's found the problem. The original plumber turned up the pressure to 1.5 bar even though it's always run happily at 1.0 before, and the pressure relief valve at the top of the boiler cuts in when it's hot. It has some obvious corrosion, so it's now down for replacement... when the guy returns from his holiday!
Alec.

 

[45yearsagasman]

Two main reasons a pressure relief lets off:-
1 The valve is defective.
2 The pressure in the system(when hot) is rising above 3bar, therefore the valve is doing its job. Get the expansion vessel charge checked when replacing the PRV.

 

[Corazones]

Thanks for your help, Pete. I have since discovered that the item which both engineers described as a pressure relief valve is, in fact, an automatic air vent. Also the fact that the system had been pressurised to between 50% and 150% higher than the official specification, and not bled of air in any other way, probably meant that some fluid was released from this vent with the air and, over time, had caused it to be corroded. Decidedly not impressed!

The manufacturers (Grant) were very helpful and gave me the part number, which I have looked up online and it's identical to what I have. I have therefore ordered one up - it cost very little - and I'll have it to hand when I find someone competent who's not on holiday. I realise this is a simple DIY screw-in replacement, after partially draining down the system, but in this case I'll leave it to the builder's plumber as I consider the builder has a liability to repair the stained oak top and so I don't want to interfere!

Alec.