This combi boiler has been running trouble free for over 3 years, and
serviced annually. Got home from shopping, to a cold house and no hot
water. Pressure on boiler below 1, checked throughout house for leaks,
no found. Increase pressure to 1.5, boiler fired up fine. Checked
several minutes later pressure up to 3, so I had to bleed off a little
water. Any ideas as to the cause please? Is it indicative of a problem
lurking? I certainly do not want problems over the Christmas/ New Year
It started with the pressure dropping, I increased it, then when it
warmed up I had to drop it again. I have just had another look and had
to drop it once more. My guess (and it is a pure guess)is that I have
now taken as much water out as I put in when the pressure had dropped!
You really need to reference this when it is cold, set it to 1bar cold
and run the system. The pressure should not rise by much more than
0.5bar when hot, if it rises by more than 1 bar then as previously
suggested the expansion vessel is suspect.
1 Did you isolate and disconnect the filling hose? A leak in the filling
valve would cause the symptoms you described.
2 Does the pressure rise rapidly when the bioler heats and fall again rapidly
as the boiler cools? If so has the pre-charge air leaked out of your pressure
vessel. A top up with foot pump may be the cure. Before doing so read the
sealed system FAQ (and your bioler manual).
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