ChauffePro · Anderlecht 1070
Boiler expansion vessel: pressure rising and falling
The expansion vessel accommodates heating water expansion. Large pressure changes need checking alongside leaks, filling arrangements and safety valve discharge.
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Why the heating circuit needs expansion space
Water expands when heated. A suitable expansion vessel provides a compressible cushion separated from the water by a membrane. Its size, condition and charge affect pressure stability. An expansion vessel for heating is not automatically interchangeable with one for potable hot water.
Watch the cold-to-hot pattern
Pressure that rises strongly while heating and falls after cooling can point towards expansion problems. A safety valve may discharge when pressure becomes excessive, leaving the circuit low afterwards. Leaks, an open filling connection or an unsuitable gauge reading can also contribute.
Assessment requires the right conditions
A professional checks the vessel, connection and charge using the correct procedure with the water side appropriately depressurised. Reading or adding air under arbitrary conditions can give a misleading result. Do not dismantle a hot pressurised system or repeatedly top it up to hide the symptoms.
Recharge, replace or resize
A vessel may need its charge corrected, but a damaged membrane or unsuitable capacity can require replacement or another solution. After work, pressure behaviour cold and hot and any safety valve discharge should be checked. The final choice depends on the complete circuit and appliance instructions.
Arrange a diagnosis in Anderlecht
Provide the make, exact model, full fault message and when the symptom occurs. Keep the appliance accessible without opening it, and mention previous repairs or leaks. ChauffePro can discuss breakdown diagnosis, repair and servicing. Availability and the proposed work are confirmed for your installation.