Should My Combi Go From 1.3 Bar To Zero In 7 Months?

[3500P5BV8]

I posted a question about my Broag 28c combi being noisy when the CH was on.

//www.diynot.com/forums/viewtopic.php?p=1637089#1637089

With the help of a knowledgeable friend, we have discovered the fault was caused by the pressure being at zero. We refilled it to 1.3 Bar, and the noise has completely stopped.

Should a boiler drop to zero pressure in the seven months of usage? It has been used a lot, especially during the cold spell. Is this normal, or is there a slight leak somewhere that needs attention?

 

[Agile]

No, but thats only because you should have topped it up when it went below 1.0 Bar.

I recommend pressurising to 1.5 Bar cold and repressurising when it has fallen below 1.0 cold.

At those pressures it typically needs repressurising every 2-4 months. A few last a bit longer, if much longer then i expect a slight leak on the filling loop.

The installer should have shown you how to repressurise it.

Tony

 

[ianniann]

I blame TRVs. I've had systems that run for years without topping up, yet now it is accepted wisdom that the pressure will drop every few months. Either gas fitters all forgot how to join pipe properly or something in the design changed. Valves pass a tiny amount of water every time they operate and I suspect that the net result of several of them operating a few times a day is a slow pressure drop.

 

[Agile]

That might be one of the causes but I am apalled by the poor quality of most of the cheap lockshield valves.

Now they use rubber "O" rings rather than a packed gland and there are differing qualities of rubber and I expect its the cheapest rather than the best which they use.

Tony

 

[Paul Barker]

If it has a plastic case turn off the domestic hot water preheat.