I have an oil fired aga which heats the domestic hot water, at least it should do but I can't get it to thermosyphon. I have plumbed it myself, and have had it working only once. On servicing the aga I haven't been able to get it thermosyphoning again.
The lower pipe from the exit is hotter than the top, and I assumed that the flow came from the top. It is in 28 mm and there are some relatively level runs which maybe the problem. I have a heat sink radiator in the loop to stop it getting too excited - some hope!! Any ideas.

Matthew, March 2010

Make sure the top pipe ( is it 28mm?) rises continously from the aga to the cylinder. so that any air in it will rise up to the vent ( you must have a vent?) Also I guess you are aware that the cylinder MUST sit higher than the Aga for the gravity heat pump system to work.

Jonsox, August 2010

Top pipe should be the hot, so follow the pipes from the Aga to the cylinder, and make sure the top one from the aga goes to the top union on the cylinder, after that try boiling it , or when the boiler is running try drainning some water off , as it is trying to refill through the retuen pipe it might pull the hot water up the top pipe from the aga and start working.

erj, March 2010