I have an Indirect central heating system.The problem started when the overflow pipe from the ch system started dripping outside. checking the expansion tank in the loft, the ch vent pipe was trickling hot water into the expansion tank. Since then, I have had a CH engineer replace the pump, the indirect cylinder tank, thermostats on most radiators,boiler serviced and the whole system power flushed, costing Â£710, and the problem still exists. There is a valve next to the pump and hot water tank, that works when the system is set to hot water, hot water and ch, or ch only, the hot water comes out of the vent pipe into the expansion tank when the system is set to hot water, either hot water on its own or with the ch as well, appears ok when on ch only.
Any ideas on this problem would be welcome, as I cant afford to keep spending and just hoping the problem is curred.
Thanks in advance for any advice, Mark.