Wood burner and unvented cylinders

[ajstoneservices]

 

[lightfoot]

Go on Tony......just say the words....it's time we weaned you off those unvented time bombs   
......you know it makes sense....it's the future.....just repeat after me......Th Th Th...St St St

Please Sir, can I have a THERMAL STORE

Repeat this mantra, tens times before you go to sleep each night...or any time you get a UVC craving   


Lightfoot.

[ajstoneservices]

  no! I cant do it, except were installing one next week ish

[lightfoot]

Ummm.....I can see your weakening .....I'll have you fitting proper wood boilers next 


PS, Congratulations Tony, I've just noticed you've recently (and quietly) joined the executive 1000 posts club...
......have a cigar and keep up the good work 

Lightfoot.

[jeando]

Ah - I see. Use the wbs to heat a big tank. then suck the heat from the tank and inject it into the UVC using a pump. Then run the system as if the pump were the one to the oil boiler....

simple - and cheap - I could even use the original oil burner circulating pump - I just need a changeover valve, and an efficient tank somewhere. But the tank needs to be sized to be able to absorb all the heat from the WBS.

Hello,

seems an awful waste to dilute all the nice heat from the WBS in a th' store (or whatever one wants to use/call it) and then feed it into the unvented store.

How about using a heat exchanger? Vented gravity loop with the heat exchanger and a sizeable heat dump on thermostatic valve (same issue as a solar heat dump) for the stove, heat exchanger in a pumped circuit either direct or on the solar coil (if you happen to have a controller with a spare second loop.)

Any thoughts about that?

Jens.

[guydewdney]

the other option is stuff the WBS, go for a plain wood cooker and a pellet boiler. We have plenty of land (5 acres, with a 2 acre empty field) and could grow / coppice willow and process it into pellets (via one of Ivans chepo pellet mills - can I have some more blurb on those please Ivan?).


hmmm

[lightfoot]

Good idea Guy.  If wood is going to be your main heat source and you have anything but a small house/heating load, then in a effort to reduce your firewood consumption and pollution and also to provide a element of automation, it may well be worth investing in a proper dedicated, clean burning, efficient, log batch/wood chip/pellet boiler and thermal store system (which could be installed in a out building if required) and there are plenty to choose from these days, so I'm sure you could find something that suits your needs and budget.  You could also have a small independent room heating wood stove as a secondary heat source for cozy winter nights etc.

Good luck,

Lightfoot.

[Brandon]

just put a PHE in, wee f&e tank for the WBS, job done. worst case, a couple of essex flanges.... don't let go of th' DOH!!!

[guydewdney]

I have had a thought...

If one set up a simple system with:- tank in the loft, heat leak rad below that, WBS below that, all in 28mm. Teed into the 28mm was an anti thermosyphon loop / dip, a normally closed valve, a pump which fed the unvented cylinder (instead of the original oil boiler), then in disaster mode, its exactly the same as a 'normal' wbs setup - ie I have a tank of very hot water in the loft, and a very hot radiator. The water cannot syphon past the dip, PLUS the valve PLUS the pump, so it will take the 'easiest route' and flow up to the tank in the loft.

I have discussed elsewhere using a heat exchanger to do the same thing - but Im now thinking that I dont need it.

Theres a pic of a rough schematic- some details like expansion vessels are omitted - but the principle is there. (I think I have also missed the normally closed valve)

[dhaslam]

Does this mean that you have a tank in the attic with no function except when there is a power cut?   Why not use the attic tank as a buffer tank and transfer heat down when needed as you would use a boiler.   It needs a high standard of insulation all the way.     This is what I am using  and will have 1000 litres of buffer tank in the attic and a normal solar cylinder downstairs.   It would take more than three fills of the woodburner to boil the store.

[guydewdney]

I had thought of that - using the pump to suck water out of the vented tank, and round - but I assumed this would be very inefficient, and take a long time for the heat of the boiler to be enough to heat the house, as it has to heat the store / vented cylinder first. With my rough sketch, the heat is available immediately.

or is it? Does the heat from the WBS heat the top of the tank pretty quickly? You have such a beastie, let me know!

[dhaslam]

You need to think of the buffer tank doing its job and retaining heat over a longer period so the warm up time is less important.  The output from a buffer tank is going to be at the top so there shouldn't be much delay in warming up.  When I was heating the house and office using a wood burner I had to use electric heaters for an hour or so in the morning in cold weather.