I have an indirect hot water system. I have just had a pressure vessel installed to my central heating system because a new radiator has been fitted as part of a loft conversion. The CH top up tank was lower than the top of this radiator, hence the pressure vessel. I now find that the water in my cylinder is not heating up. If I set the system to hot water only, the boiler cuts out on its thermostat almost immediately. I suspect that the pressure in the coil from the new vessel is preventing the normal gravity flow from the coil in the cylinder back to the boiler. Currently trying to reduce the pressure on the vessel to try and restore this flow. The central heating is working fine. I have no motorised valves in the system so it is normally hot water or both water and heating. Any ideas anyone?
Sorted it. Immediately after first post here, decided to check for an airlock in the cylinder heating coil. Cleared it by restoring pressure in pressure vessel and cracking open the old expansion/vent pipe for the CH system which had been blanked of with a screw-in plug.