Combi Boiler Maintaining 3 bar whilst hot.

[AndyStone]

I've got a Worcester 280 with a cold pressure of 0.8 bar (just to be different). The house is only a 2 bed semi with 2 rads downstairs (on inverted loops) and 3 rads upstairs.
I've been told this should be no where near capacity for the boiler but when the CH is on it stays far too close to 3 bar for comfort.
It doesn't seem to be venting yet but obviously it's getting a bit close for comfort.

Any ideas ?

Also any tips on how to balance rads ?

 

[breezer]

I am not a plumber or heating engineer, have you checked your expansion vesel's air pressure?

see simon's reply for balancing radiators

//www.diynot.com/forums/viewtopic.php?t=1909&highlight=balancing+radiators

 

[AndyStone]

That may well be it !

The manual says it should start off with 0.5 bar but it was 0.1 to zero.
I did charge it with a pump and brought the remaining pressure up with the filing loop but when I switched the CH on it sounded like I had a lot of air in the pipes.
Has this just forced air into the whole system including the rads ?
Surely the air should remain trapped in the expansion vessel ?!

As I've fitted an automatic air release valve at the top of one of my inverted loops it should all vent out again.

Have I got this wrong ?

 

[breezer]

i am not a plumber or heating engineer and i do not know what the valve you refer to is, but try bleeding the radiators then check system pressure again.

The expansion vesel is like a balloon in a sealed tank, you can only blow up the ballon (unless it is split, which is unlikely)

 

[Ant]

Do not confuse the pressure of the pressure vessel - mine can be checked with a tyre valve - and the pressure of the central heating circuit measured on the boilers gauge. You could recheck the pressure in the pressure vessel to confirm it is correct - if not it would point to the fact that it may be split. This happened to me and the boiler pressure would rise until it vented through the overflow/vent pipe.
It may be worth checking with the manufacturer as to the usual working pressure - you may be worrying unduly.

 

[AndyStone]

Cheers guys.

Despite yeterdays fears of introducing air into the system I let it cool down all day today and it returned to the 0.8 bar I set it at yesterday (0.5 bar air pressure which covers my static head plus 0.3 as it says in the manual).
Also heard no air when I started it up again today.
Best news is that the max pressure with the CH on last night was about 2.25 so huge improvement.

The balloon analogy was useful !

BTW Whilst trying to convert psi to bar earlier I found this jolly useful link :

http://www.ex.ac.uk/cimt/dictunit/ccpress.htm