I have a conventional Y-plan vented central heating / hot water cylinder pumped system with a gas boiler. I was thinking of adding a wood burning stove (e.g. the Morso Squirrel) with a backboiler to the system, as an alternative/supplement to the gas boiler, but I can't see an obvious way to connect it up. Would it be best to get a new cylinder with two coils or a cylinder with direct connection for the backboiler (as well as a coil), or is there some way of plumbing it into the existing boiler loop?
This must be done carefully, as if done wrong, it very easy to get a dangerous situation. That means that the back boiler must have a good unvalved gravity circulated loop. This is because a solid fuel appliance has poor control and isn't suited to the manual reset overheat controls that gas and oil can use.
The two main safe ways of doing this:
Using a neutral point device, such as a Dunsley Neutraliser.
Replacing hot water cylinder with a heat bank. This can have extra tappings that can act as a neutral point for a gravity circulated boiler. A modern boiler can still use the rapid recovery coil, if pressurised operation is required.
(1) Will be cheaper.
(2) Has the advantage of also providing mains pressure hot water if your mains water supply is good (it can run gravity fed if you must). Also, the hot water cylinder now has corrosion inhibited water, so will last longer.
With forethought, both systems can be designed to be upgraded to solar heating if there is any prospect of putting panels up.
Don't design a homebrew system to connect up a solid fuel boiler unless you are qualified to know the issues involved, as most such systems are deathtraps waiting to explode.
do heat banks too. The stove and boiler can heat an integrated heat bank which will provide heat for the DHE and space heating. Also solar panels can be attached.
Look at the Solid Fuel Association and down-load their 'Link-Up' guide.
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haven't looked at this in a long tome, but seem to recall it recommended a controller which had no electronics. I wasn't very impressed with it.
There's lots of ways of linking the systems but the solid-fuel boiler should be open-vented and should be able to discharge steam in the event of a system failure. Pressure relief valves should still be fitted to the boiler.
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