wood burning stove problem with hot water circuit

[jgray]

Recently installed wood burning stove - gravity fed indirect cylinder and pumped radiator circuit. Once the flow pipe from the boiler gets too hot to touch on most occasions the stove boiler starts hissing and the return pipe is always luke warm. To get around this problem we activate the pump by turning the thermostat down. Having read several plumbing manuals and numerous web searches I understand the gravity flow pipe should always rise to the cylinder and fall on return, in our setup the flow pipe is higher than the connection to the cylinder it Ts off with vent pipe, runs horizontally and then vertical drop approx 8 inches into the cylinder coil. The return exits the cylinder with immediate short elbow joint vertical climb approx 2inches with elbow fitting then runs horizontally and then falls. Plumber convinced the system is air locking and is not concerned re setup of pipes. When the pump comes on there is a blup blup sound, I think in the vent pipe. Please can someone advise me on what to do next, we have put a lot of money into the boiler stove and would really like the benefits.

 

[WHPES]

I think you've answered it in your question - You need to relocate the cylinder so that the hot water rises to it and falls from it in a steady gradient. It needs to be sufficiently high enough above the stove for the gravity circulation to work.

 

[paul bone]

Hi, on the gravity system you must have a continuous up run for this kind of system to work correctly, you must have a heat leak.
Air can be a big problem on the best of installations where gravity is concerned.
best way to install the cylinder is in a room above the wood burner so you have nice vertical rise, if not possible then make sure you have enough rise on the pipework and min size of 28mm on primary pipework.
hope this helps
Paul