Wood Heaters – Radiant or Convection?

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Re: Wood Heaters – Radiant or Convection?

Postby offgridQLD » Wed Jul 15, 2015 10:51 am

Well we finally after a few years of stuffing about purchased a wood heater (get it in a week or two) . We were looking at the Nectre bakers over but for yours they only made the one model for smaller homes up to 140m2. I was looking about on the net and noticed they had updated there webpage. I also noticed they now have a BIG bakers oven that will pump out about 22kw and is large enough for our main open plan living area. Not to mention the actual oven section on the bottom is much more generous. More like the size of a typical modern oven.You can also cook on the top of it but I don't see myself doing much of that (well no stir frys in the lounge anyhow :lol: ) Just nice to have something cooking over winter on special occasions.

Though I like that in a SHTF situation I'm not reliant on gas or even our offgrid electric system for cooking.

Its over 200kg and I need to get a base made up for it and install it. Should have a good 5m or so of flue so should draw well. The flue will be exposed for the first 3m to the ceiling and vents will be installed above it to duct/transfer heat to two other rooms when needed.
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Re: Wood Heaters – Radiant or Convection?

Postby Cherokee Solar » Thu Jul 16, 2015 9:16 am

offgridQLD wrote:Its over 200kg and I need to get a base made up for it and install it


Hi Kurt,

My unit looks almost exactly like the one in the photo and being way down in the SE corner and up in the mountains where it is as cold and misty and cloudy this winter as I can ever remember here - that thing earns its keep. It hasn't been warmer than 5 degrees for days and days on end and the sun is missing in action. I'm barely making 2kWh - 3kWh/day here. Batteries at 65% full this morning - I've had to cut back severely. :? What's going on? :? Still, extreme conditions are useful as they test your systems. It is very toasty in the house though. :D

Yes, they are very heavy units and an el-cheapo trolley will fall apart if you attempt to use one to move it around. It took five people to lift it up the stairs at the front of the house. A better quality trolley will move it no worries, but use an el-cheapo at your peril - the axle broke on mine even though it was rated to 250kg! (cheap rubbish - so I picked up a solidly built one to replace it).

The base if installed over a timber floor is made up of thick fibro cement sheet with floor tiles. Screw the fibro sheeting to the floor. You also have to be aware of the distance between the wall and the wood box and leave enough tiles at the front of the box to ensure that your nice timber floors don't get burnt by things falling out of the wood box from time to time. Just sayin...

Cheers

Chris
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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Re: Wood Heaters – Radiant or Convection?

Postby offgridQLD » Thu Jul 16, 2015 9:38 am

You might have the original smaller bakers overn (that's if its a nectre brand) is the air controlled with a big round knob that you turn like an old safe dial?


I have a little trolly made from RHS 3mm x 40x40 ss that has several caster wheels designed to move pianos and slate pool tables. Plan was to use the jib on the tractor to lift it off the trailer and lower it onto the trolly on the back deck using heavy ply sheets to get a smooth rolling surface . Then I am on the same level as the lounge room floor.

The installation manual lists 15mm cement sheet minimum with 300mm in front and 200mm each side. Rear clearance is 125mm min.

I'm more concerned about damaging- cracking-scratching the tile area that it sits on. Though I have had some heavy things (slate pool table) moved across some of my tileing jobs in other homes in the past without issue.

Most likely will just get it installed ready for QLD summer....on well

Kurt
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Re: Wood Heaters – Radiant or Convection?

Postby Cherokee Solar » Thu Jul 16, 2015 11:20 pm

Hi Kurt,

No it looks almost exactly like the unit in the photo. It is made by Thermolux and is the Gourmet cooker.

Yes, 15mm Fibro is the way to go. I didn't manage to crack any of the tiles but we were all very careful when moving the monster, but the timber floor (19mm Sydney Blue Gum tongue and Groove over timber joists and bearers) is pretty solid too and I added extra joists under that point in the floor to support the load - you can never be too careful.

Yeah, 15mm flooring plywood should take the load easily, but don't let the span be too far without it being supported underneath.

Good luck and let us know how it goes. It looks like a good unit.
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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Re: Wood Heaters – Radiant or Convection?

Postby offgridQLD » Thu May 25, 2017 10:36 pm

Finally...two years later :oops: I got some motivation to remove the fake gas log fire place and remodel the lounge wall for the bakers oven.

Works really well. Wasn't burning anything special in it just some well seasoned black wattle that grows like weeds at my place and it knocks out some serious heat. large open plan area with very high ceilings and all rooms open. Wasn't that cold tonight its about 13c outside but toast 24 throughout the house.

From stone cold lighting the fire the oven takes about 45min before you achieve 180C as there is a bit of mass to get hot. Checked 180c on the large front anolog temp dial . Verified it was reasonably accurate with a digital probe. I was supersized how controllable the oven temp was by just opening the air bleed on the bottom door. I was expecting to have to do a lot more tweaking and fiddling about to maintain a stable temp over 1hr cooking time or so but it was easy.

I tried to add some more thermal mass to the install with 250kg of stacked stone behind the heater attached to 70kg of 15mm cement sheet. The mass is there though I was surprised that very little heat radiates from the rear of the oven. The stone is still warm after the fire is out but the stone wall is not as hot as I was expecting it to get.

I noticed you can't choke the fire down completely. Shutting the top door air slider and the side glass air wash slider off completely the fire still has a reasonable air supply to it. I then noticed the small (always open) third air slot for the door glass air wash even when fully closed. Part of the parcel with tougher air pollution regulations and not a real bad thing as no one wants a smoldering fire with smoke outside and dirty black door glass from a overly chocked fire. It actually makes controlling a slow but clean burn easy as you just shut all the air controls 100% and it ticks along nice and reasonably long burn times are still achievable without choking to much.

Roasted a few spuds in it covered in foil (as I didn't want a fresh paint smell to a expensive roast :lol: ) first burn is a little stinky though has settle down now..... Overall happy.

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Re: Wood Heaters – Radiant or Convection?

Postby Cherokee Solar » Fri May 26, 2017 11:16 am

Hi Kurt,

Long time... Hope you are well and that the floods up north earlier this year haven't been a problem for you.

That Nectre unit is an excellent unit and I considered that one. I recently installed a Nectre MEGA which is an awesome unit as it has a huge wet back / boiler for the hot water and hydronic radiators. Just the thing for when the outside temperature is hovering around 3'C (you might not get as cold up your way! ;) ).

With that lever on the left hand side of the unit, just a gentle reminder that if you are not using the oven, keep the flue gases going straight up the flue (rather than around the oven). The thing is that as the flue gases go around the oven, they cool and form creosote. You want to keep the exhaust gases as hot as possible because creosote is corrosive to metal. That is the other reason you can't burn green or wet timber as the fire cools as energy is directed into boiling off the sugars or moisture in the firewood and the exhaust gases form creosote.

Far out, this autumn has been very cloudy. Just keep adding more panels.... :lol:

Chris
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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Re: Wood Heaters – Radiant or Convection?

Postby offgridQLD » Fri May 26, 2017 8:33 pm

Thanks for the tips. That nectre mega is a monster. what was it rated at 30kw nominal output or something crazy like that? Huge fire box less log splitting ;) I did notice the clearances are large to on it from anything flammable.

We had the option of the wetback (just a small box with two pipes that replaces the 3 flat fire bricks at the back of the heater. So can be fitted at anytime..or made up myself with some drilling required. Though we have a new 30 tube solar hot water system and no need for radiators in QLD. so most likely will stay as it is.

I'm kind of glad I dint go larger for my needs in QLD it's about 13c outside now and we put it on and cranked it up a little high to make some pizza and really get the oven part hot. I had the two ceiling fans on low (in reverse direction to mix the air) I was down to a t shirt and shorts. It was most likely running at a good 20kw or so but impressive in the large open plan area with all the house opened up to. I did warp one of the SS baking trays a little. I was able to pop it back into shape when it cooled but will most likely tig weld in some bracing ribs in the bottom of at least one of them that I use for pizza's up top at full throttle :twisted: or get s square pizza stone for it.

Run on medium setting with some cooler weather later in the year it should be a good size.

I did notice that even with the flue gas bypass going up the flue the oven still gets hot and holds close to 180c. It could just be residual heat from when I made the pizza a few hr ago but it hasn't really dropped from around 180 for some time....see in a few more hrs.

Much better air wash on the glass than my dads now 30 year old nectre mark 1 LE I think it is. That would soot the glass up a bit as it slow burned over night. The glass stays Cristal clear even the next morning on this one though most likely cant be throttled down as much.
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Re: Wood Heaters – Radiant or Convection?

Postby jimbo » Sat May 27, 2017 8:42 am

Where are you in QLD? I'm on the sunshine coast for work and holiday and the weather has been amazing. Got sunburn in May! Unheard of back home :)
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Re: Wood Heaters – Radiant or Convection?

Postby offgridQLD » Sat May 27, 2017 9:48 am

Sunshine coast hinterland near Maleny.

Yes winter is great in QLD 20 - 27 day time and cool in the evening but not to cold.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: Wood Heaters – Radiant or Convection?

Postby jimbo » Sat May 27, 2017 9:50 am

Ha, probably heading that way today or Monday.
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