wrote:

my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar and
it held this until the central heating had been on again, when it had
again dropped to 0.75 bar. This has continued all week it never drops
below 0.75 and works o.k. i can see no apparent leaks and the pressure
release valve has not discharged any water, the maximum pressure
reached when running is 2 bar. The only mention in the handbook of 0.75
bar is the pressure at which the expansion tank is pre pressurised at.
has anyone any ideas

How many rads is it running?

My HE35 only registers a pressure rise of approx 0.8 bar going from cold
to hot. That is with 10 rads.

I tend to find that my system will slowly loose a little pressure over a
couple of weeks or so if you top it up to 1 bar, it takes the addition
of the equivilent of a couple of cups full of water to go back to 1 bar.
If you leave it, then it stabilises at about 0.8 bar. The difficulty
finding such a low volume loss, is that it will probably evaporate
rather than ever appear as water anyware.

On my system many of my rads are pretty old and I don't totaly trust all
the valves either (I am sure the previous house owner must have cobbled
together some of the collection of rads by raiding skips! - there are
about three different designs). I was half expecting lots of things to
start dribbling when I converted it to a sealed system, but so far
nothing has actually sprung a noticable leak.

--
Cheers,

John.

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