Can I plumb a Wood Stove (internal back boiler) to C/Heat

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I imagine this isn't a simple as it sounds with modern boilers, what I am looking to do is plumb in a Wood Burning Stove with an internal back boiler to a standard gravity fed gas central heating system so the stove also heats the CH fluid sharing the rads around the house with the gas boiler. The gas boiler is a Worcester 14/19cbi open gravity feed with Honeywell Smartfit controls.

Where and how would you plumb it into the loop? I'm no expert but I've fitted my own Combi System so have a good DIY plumbing knowledge. Problems which come to mind (but may not even be problems) are

if plumbed in before the boiler will it shut the boiler down if the CH fluid gets too hot after the stove?

if plumbed in after the boiler but using the existing pump how do I get round water not circulating when the boiler and pump aren't on demand... will the back boiler boil the CH fluid causing vapour blocks etc?

or can I simply add an extra manually switched pump just for the stove heated fluid and circulate going into the main loop after the boiler, having the pump on the return before it goes back into the main loop (again after the boiler) if that makes sense?

Any advice would be very gratefully received.
 
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There are several issues to contend with and the recommendation would be to get an experienced engineer to visit and advise how its best done.

The big potential problem is to stop the stove output circulating through the CH boiler.

Some will recommend a Dunsley neutraliser although the same effect can be obtained with simulated pipework.

Another method is to put a non return valve on the boiler return and use a pump and a non return valve on the return to the stove. Then power the stove pump from a thermostat on its flow pipe.

A safety issue is that the stove has to be supplied from a big header tank so that it could boil away the water if the pump fails. However the non return valve might still have a flow direction resistance too high to allow enough gravity circulation. To counter that the non return valve could be left out and a gate valve fitted after the pump to create resistance to reduce the flow through the stove when the CH is on and stove off.

So in all there are many considerations to be made and it might still need modification after first connection if it does not work as well as expected.

Tony
 
Thanks for the quick reply Tony,

I always assume nothing in life is as simple as it could be :D

As you suggest, I'll definitely get advice if trying to run the systems in tandem which was my plan.

I guess another way would be to totally isolate the boiler with two ball valves (if even needed if the boiler is switched off?) and just switch it off when using the stove. I could then run either just the stove for heat or the just boiler for heat and DHW. I presume if doing this the existing pump wouldn't obstruct the flow too much when it is off and the extra stove pump is running (this would also give the back boiler a gravity fed header tank as it would use the tank normally used for the boiler?) - but then I'd also have to ensure the control valve when switched off wasn't just diverting to the water tank only I like your suggestion of a thermostat to switch the extra pump for the stove, that didn't occur to me.

Nic
 
You might find this thread advantageous.

Have you got gravity to a cylinder with a pumped CH circuit?
 
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You can put a SINGLE full flow valve on the RETURN to both boilers and manually change them over.

However even that is not totally correct as if you close the the stove valve when its in use it will potentially overheat as th steam produced miy block the slow of water down the same pipe.

It would not be very dangerous as it would still all be at atmospheric pressure but might crack the heat exchanger.

If you make any connections to the stove pipework you must replace a plastic F&E tank with a metal or fibreglass one that will not deform and fail as a plastic one will if the stove starts boiling

Tony
 
That all makes a lot of sense Tony, thanks, I'm glad I asked rather than just trying to figure it out blindly. Still I guess that's what this site is all about. Thanks very much for your help.

Goldspoon, I've searched for the topic you've described and it doesn't come up on here (well, not that I can see) and even then I'm not sure which part of the topic you mention I need to look at either, any chance of a link?
 
The whole topic also has some useful info so thanks for the link Goldspoon. Looks like other are far more ambitious than me with what to connect to their heating too :D
 

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