Are boiler stoves much less efficient?

[charlieb]

I've triumphantly managed to buy a Morso Dove on ebay very cheap. It was cheap because the insert boiler had sprung a pinhole leak, but that doesn't bother me as I'm taking the boiler out in any case and reverting to room-only heating.   But I'm surprised just how much new baffle, etc, I need to install: basically the sit-in boiler, a proper Morso one as far as I can tell, sits at the back and over the back-top of the firebox, but it replaces all the cleverness of the stove: ie no pre-heat air coming in the back, no firebricks or anything.    Two exploded diagrams of the stovewithboiler and the stovewithoutboiler are at http://www.stovespares.co.uk/morso-dove-multi-fuel-stove-spare-parts.html .  I'm amazed at the difference. Anyone else?

[dhaslam]

Yes it seems that  boiler and non boiler versions  of the same stove can be quite different.     It is very odd that the efficiency  of the two versions turns out to be similar in tests  when you consider how much hotter a dry stove can burn. 

[Billy]

Certainly my Squirrel without the boiler ran hotter and cleaner.  The boiler just cools the back of the fire.  It would be much better with a loading valve to keep the water temperature up.  If I burn it real hot then it's fine but the TV starts to melt which upsets Mrs B.   

During a period of fiddling on the wet side I did disconnect the boiler and fill it will some dry sand.  This seemed to work remarkably well and the boiler survived.

billy
 

[charlieb]

Yep Billy, that's my default plan if I can't get nuts off.   But the stove's actually in such good nick I think I'll splash out the £200 or so to get proper baffle plates, etc.   Anyone want a leaking back boiler for a Dove, carefully removed?

[Baz]

I wonder which they designed first. It's difficult to see what the extra bits do but I think it may have an access panel for sweeping and other bits are like that to enable replacement without complete dissassembly. I suspect they were being all clever with the non boiler but when they then came to the boiler version they had realised the faffing around didn't really help much.

[charlieb]

I see what you mean Baz. It does look a bit like that.  But my squirrel has some sort of air inlets at the back that make for jets of flame when there's fresh wood in there.  I've always thought of this as 'burning off the smoke', which is one reason why stoves are so much better than open fires. (it also makes a great pattern to watch - which I've done a lot of).     Certainly there's no way the dove could have done that with the boiler in - I'm hoping there's something in the baffle mechanism that does equivalent once I've put it in.

[Ivan]

Yes, efficiency is generally about 10% lower WITH a boiler on a woodburner, but it depends on the design. If you can put the boiler in a post-combustion location, then the efficiency shouldn't be affected (a la "wood boilers").

Download the Sedbuk database - which should give you independent test results for stoves with/without boilers. This is where I got the 10% figure from (for my Hunter stove)

[charlieb]

Has anyone got thoughts on whether it's worth keeping the insert boiler (that apparently has a pinhole leak)?  It's pretty damn rusty to look at, but feels solid enough. Heavy, so I guess a bit of scrap value and I don't really want it lieing around, so unless people think it's definitely worth keeping (or passing on to any of you lot..) I'll scrap it this weekend.