Pellet fuelled donkey for hydronic floor heat.

[mudguard]

Hi all,
This is my first post, although I have been lurking and learning for some time from this great site.
I have an unusual project and would like some info and input if possible.
I live in Australia, and we don't have as cold climate as some parts of the US, but my home is in need of heating this winter, it is not long been completed.
Secondly we don't have the take up of pellet burners and boilers to the extend to the US , so sourcing parts etc is not convenient from here but it's doable.

My home has hydronic floor heating installed in the concrete floor, it is currently hooked up to solar water panel that transfers heat into a 400 litre tank that is then circulated through the floor. This is not sufficient to heat the house through the darkest part of winter or in times of overcast weather, but it has done a great job of warming the floor coming into and out of winter. The building also allows winter sunlight into the house for warming on clear days.

The project is to boost the 400 litre storage tank with a pellet / biomass / wheat burner.
I have secured all the important parts from a Harman P43 pellet stove, that is the entire auger feed, burn pot assembly hooked up to a 240v auger motor (Australia uses 240v not 110v).

The burner set-up is going under a 135 litre water heater tank that previously used a LPG gas burner to heat domestic hot water. The heater tank will be plumbed to the larger storage tank with a circulating pump. We call a water heater like this a 'donkey'.

The questions I have initially are easily answered by those familiar to the Harman heater.

1. What is the flame height measured from the burn pot of a Harman P43 at full throttle? (I need to gauge the placement of the burn pot relative to the bottom of the heater tank.)


Constructive suggestions welcome.

For those concerned with safety, both tanks and burner are outside the house, there is a controller with the target temp of the heater at 55 degrees C. There will be some other safety cut-outs added as the build progresses based on a thread from this forum, by 'snowy downs'.


Steve

 

[Lake Girl]

There are stoves that are left relatively intact but utilize a cross-link to a water heat system. Bioburner has a photo of his Harman with the cross-link in his avatar.

Glad to hear that the donkey boiler is away from the house and that you are adding safeties. Just wondering if a system like Bioburner's would be more effective as it heats the room it is located in but provides hot water that can be circulated ...

Good luck with the build - hope you have a mild winter!

https://www.hearth.com/talk/threads/harman-pc45-with-now-installed-crosslink.93158/

https://www.facebook.com/pages/Crosslink-Conversions-LLC/260782207405466
http://crosslinkconversions.com/

 

[mudguard]

Thanks for the reply
In our previous cottage we had a wood fire and it was a messy thing to have in the living area, twigs and smoke and so on. So in our new house we opted to go with the slab heating and not have an indoor wood heater of any kind.

As we have the storage tank, pump and in floor all in place the boasting with the donkey suits our needs.

So - Harman flame height anyone?

Steve

 

[railfanron]

9 to 12 inches. That's pretty much full height in my avatar picture.
Ron

 

[mudguard]

Cool - thanks Ron, for the reply.
I can work with that to set the space between the burn pot and the bottom of the tank.

Cheers
Steve

 

[Lake Girl]

9 to 12 inches. That's pretty much full height in my avatar picture.

railfan Is that flame height dependent on the fuel type? mudguard, what fuel are you planning on using? I know Harman recommends a mix of pellets and corn (common fuel in US) for their stoves. Not sure what the difference is w/wheat compared to corn . Would hate to see you set it up based on one fuel type and find a big difference with another fuel.

 

[Lake Girl]

had a wood fire and it was a messy thing to have in the living area

Same here with the wood stove so we switched to an outdoor wood boiler. The beast liked to eat lots of wood - so much loading of large pieces of wood that I had a nephew ask where I was working out because of developed biceps They are a lot of work too but the mess is kept outside. Older and wiser now (maybe!) so have gone to the pellet stove

 

[johninwi]

The p43 was just a pellet stove, look at the pc45, they were multi fuel and wheat i believe was included as a fuel. You may be able to get the parts of the p43 to work but you might want to build a "cap" for your burnpot like the pc45 has, it holds the heat in better for burning fuels that aren't as cooporative as pellets. The 45 also has a stirrer for the burn pot that attaches to the end of the auger, the stirrer works well for breaking up corn as it burns, (the corn melts together), might be something to consider in your build if your going to be experimenting with different fuels.

If your board from the 43 has dip switches this pic from bioburner may help. I would guess the board is the same as we have here but it's just a guess.
Have you looked at the Boiler Room section of the forum? May have a few ideas for you to borrow too.

Keep us posted, be intrested in what you build, best of luck.
Another fuel that you may have available is olive pits, a former member here sells them in your part of the world, google "cheapheat australia"

 

[mudguard]

Thanks for the tip on the PC45, will see how I get on with the P43 parts I have now.

Thanks too Lake Girl, will have to be flexible with the burner position on my build re flame height, guess I will run a test before I settle on a final pot position.

BTW I'm missing on support bearing / bush assy, see circled in diagram below.
It supports the shaft of the feeder arm. When I got the feeder arm it had the bearing captured between the plate and the arm but not the bearing at the other end. My supplier is telling me this bearing support cannot be ordered??? Seems odd.
Any one there familiar with these parts, an agent maybe.

Thanks
Steve

 

[doghouse]

Had to re-read the post to find out what a 'pellet fuelled donkey' is. Although, it would produce some interesting post consumer waste.

 

[johninwi]

i googled flange mount bearings, numerous hits such as this
(broken link removed)

this one toward the bottom
(broken link removed)

and considering the speed it runs at a piece of steel 6 or 8 mm thick, drill a few holes, would support the assembly just fine for at least the testing stage of your project.

http://www.primebearing.com/SAPFL-200-Series/

 

[mudguard]

Thanks for the links for the flanged bearings.
I found the maker of the one used by Hearth - http://www.triangleoshkosh.com/
Trying to find a distributor near to me (Australia), interestingly these are used in lightweight aircraft ! as apart of the control system - yikes.

but you are right I can cobble something simple together for the time being, and then find a flanged bearing/bush as I go.

Cheers
Steve

 

[mudguard]

Hi All,
life gets in the way sometimes, just getting back to the floor heating donkey project.

As I have only started with parts of a Harman P43 pellet stove, I have fabricated a base that holds the tank and mates with the burner. The burner is mounted on rails so it can be rolled away from the tank for cleaning etc.

A question for anyone who is familiar with the P43.
Where does the combustion fan draw air from? and am I correct to assume it blows it into the 2 holes in part 2.6 ( see diagram above in an earlier post)

Will post some pics soon

Steve

 

[Bioburner]

The burn chamber on most pellet stoves is ran in a vacuum and the supply air is then directed through the fire pot etc. and the exhaust is run over or through exchangers.

 

[bags]

Sounds like a cool project. Good Luck! Radiant and thermal mass gives you a huge head start. It's a damn shame we can not set out discarded jugs and store some sun shine for those overcast days. I have always wondered about bottling kids energy and selling that. Instant gazillionaire over night.

Bioburner is about the best resource here. I do radiant floors and thermal mass with the OWB and it is awesome but requires a lot of firewood. Also domestic hot water. Happy with it just beat down dealing with the wood required. Have you looked into pellet furnaces and boilers for info? Might discover some pointers there you can incorporate.

 

[mudguard]

The burn chamber on most pellet stoves is ran in a vacuum and the supply air is then directed through the fire pot etc. and the exhaust is run over or through exchangers.

Thanks for the reply, now that I look at it that way, the P43 does draw the air out of the chamber rather than blow it in. Obviously it is for a reason, I would have thought that blowing clean air in would be easier on a fan set up than sucking the exhaust through a fan with all the heat and grit etc?
Can anyone shed some light on why this is the common arrangement?
Cheers
Steve

 

[Bioburner]

Well the feed systems used to have fires go into the feed bin because of the hot exhaust trying to find a way out.

 

[Deromax]

Blowing into the fire chamber will make any potential leaks to expell smoke in the living space. Sucking from the chamber will merily make leaks admit some air inside, which is obviously safer. They had to design fans that work in high temperature but this is not a problem. There are manufacturers (I know of Drolet) that have a dual system, both blowing and drawing, and they are promoting the advantages of this "zero pressure" system.

 

[Bioburner]

I see that may be advantageous in using the dual fan system in keeping the burn pot possibly cleaner when the stove loosens up and more leaks develop around gaskets etc. But gaskets are very cheap vs the need for two motor fan assemblies. The more electromechanical a device is the more possibility of failure vs a good simple gasket.

 

[mudguard]

Hi All,
I have finally made the first test firing of the bio-mass burner for the hydronic heating in our house. We intend on using wheat as fuel, but have started with regular wood pellets to get it going. It uses the auger and burn pot from a Harman P43 / 105, everything else has been made from scratch.

The current set up is as follows:
- The boiler tank holds about 100L (22 Gallons?) of water and is vented to the outside
- 18m (60ft) of 3/4 in copper tube is coiled in the boiler and carries the heated water the a holding tank for the floor heat.
- The burner pot is under a 6 inch tube - heat gases go up thru tank, inside lid and then down thru 3 x 4 inch tubes and out thru the exhaust fan.
- The control is by a thermostat and two asymmetrical recycle timers that give me essentially two speeds for the auger, one fast for heating and one slow for idle, (inspired by a post by member Snowy Rivers).
- Tank is yet to be insulated, Lid is insulated with vermiculite mix.
- Making some turbulators today to go in the tubes, first burn the exhaust temp was 70 c (158F)

I would like to also run the fan at half speed for the idle setting and would like some advice.
Unfortunately the fan motor I have cannot be run at two speeds (240v, cap start, cap run) apparently if I had the Permanently Separated Capacitor version I could add a speed controller.

Where I live (Australia) pellet boilers are very very rare, so I don't have access to examples.
Do most pellet boilers have variable speed combustion fans?

Another option to reduce the fan draw would be to add a damper to the outside to reduce the speed of air thru the burn pot, is this metod used at all in boilers?

Any advice welcome.

Steve

 

[Bioburner]

Long post on your progress.
Not all boilers use a vacuum fire chamber. I have a Kernal Burner-Amaizing boiler(100k btu) and the pot is fed air from around and through holes in the pot and has a 6 inch vent with a barometric damper. When heat is called for the fan is activated and the feed is fed from the bottom. Have to have a delay of feed pump when the feed is shut down to allow the pot to cool down without boiling the boiler and then an occasional circulation to keep the remaining fire from overheating the boiler.
While the system worked well it was way to large for my newer home so was wasteful. Now if someone needed that many btus it would be a good unit. My home does not need much more than 12k