Getting ready to upgrade

[Highbeam]

I also have a Windhager Biowin. Can you explain what a "batch burn" is and how you set it up?

As treehouse used it, batch burning a pellet boiler just means running the boiler at high output (or most efficient output) level constantly to reheat his storage. Then shutting off until the storage cools. That is different than modulating pellet boiler output to try and match the heat load which varies and is less efficient.

 

[Sparky978]

As treehouse used it, batch burning a pellet boiler just means running the boiler at high output (or most efficient output) level constantly to reheat his storage. Then shutting off until the storage cools. That is different than modulating pellet boiler output to try and match the heat load which varies and is less efficient.

So how does he run his PB at 100% output constantly? I would think that it would start to modulate at some point. Unless he actually watches it and when it starts to modulate he sends it into burn out mode.

 

[maple1]

So how does he run his PB at 100% output constantly? I would think that it would start to modulate at some point. Unless he actually watches it and when it starts to modulate he sends it into burn out mode.

'Then shutting off until the storage cools'

 

[nhtreehouse]

Hi @Sparky978 ,

I have the Windhager set to maximum boiler setpoint, which I believe is 176. I have a conventional Thermovar, a LK823 setup, much like you would setup any wood boiler hooked up to storage. Plumbing is really straightforward. I've got mine piped with 1" copper, and run an alpha on the lowest constant speed setting. Mine runs about 7 gpm at 14 degrees T.

I turn on the pellet boiler when the top of the tank reaches close to the ODR target, which obviously fluctuates with the outdoor temp. Once the boiler fires, I keep it on until the return temperature of the pellet boiler reaches 160.

The boiler's output temperature isn't the 176 number but rather determined by the flow rate and the regulating temperature of the Thermovar. I see the Windhager settle in at around 160-162 for a burn. Towards the end of the burn, the boiler temp does rise as the return temperature rises. But it happens quickly, as the boiler is putting energy into your storage and moving the thermocline down.

I've got a 150 (15kW or 51kBTU/hr) unit and about 120 gallons of storage. My run times are around 2.5 hours on average.

I don't know if a image would be helpful or not, here is the last complete burn:

bT = boiler temp (ya know, the hot side)
LKAB = Boiler Return (ya know, the cold side)
LKA = The "A" port on the LK valve, coming from the bottom of storage.
pBR = crappy beer, or if you're a hipster, it's the pellet boiler return. This sensor is over in the tank several feet of piping away.

The system which logs the data only logs when the boiler is being called to heat the tank. Those extraneous lines are the graphing software trying to connect the dots from the last full burn to the next.

Anyways, it works really well. Super reliable and I've had no issues with it. In the biomass sticky there are some control systems like this described. I'm certainly not the first to do this.

 

[nhtreehouse]

Oh, and I should have said ... because the boiler never reaches the setpoint, it runs wide open at 100%. It may modulate a little at the very end of the burn as the return temp increases, and the thermovar opens. But if it does, it only modulates for a few minutes as that pellet boiler return temp is really moving fast.

 

[Sparky978]

Oh, and I should have said ... because the boiler never reaches the setpoint, it runs wide open at 100%. It may modulate a little at the very end of the burn as the return temp increases, and the thermovar opens. But if it does, it only modulates for a few minutes as that pellet boiler return temp is really moving fast.

Thank you
Now I have a better understanding of how your system works. Very helpful.

 

[huffdawg]

Your underground lines suck.They are going to make you cut a bunch of wood for no reason.
You should count on abondoning them and putting in new lines sprayed in place with underground rated spray foam.

Care full with that one , I spray foamed my pex lines with closed cell foam about 8 years ago. I'm now seeing a nice melted path above my pextubing. I'm thinking the foam is starting to break down.

 

[salecker]

Care full with that one , I spray foamed my pex lines with closed cell foam about 8 years ago. I'm now seeing a nice melted path above my pextubing. I'm thinking the foam is starting to break down.

I would be talking to the spray foam guys about that.
Mine are still good after 8 yrs no sign of any melt

 

[huffdawg]

I would be talking to the spray foam guys about that.
Mine are still good after 8 yrs no sign of any melt

Is your ground dry?

 

[3fordasho]

Care full with that one , I spray foamed my pex lines with closed cell foam about 8 years ago. I'm now seeing a nice melted path above my pextubing. I'm thinking the foam is starting to break down.

I get all set to go with foam in trench and then I see stuff like this.. I wonder if it's got something to do with the expansion/contraction cycle the pex goes through as water temp changes. Regular and oxygen barrier pex move quite a bit. pex al pex is much more stable so I was thinking of using that in the trench.

 

[salecker]

Is your ground dry?

Hi
I am not sure what you mean by is the ground dry?
We live in the bottom of an old glacier formed lake,300+ ft of clay.

 

[Seasoned Oak]

I suspect simply that the green wood is hampering your boilers ability to get & stay hot enough.

.

Bingo. Cant expect much heat from green wood. Id try to get few boiler loads of certified dry wood and see what difference it makes first. I wouldnt be surprised if wet wood decreases performance by 50% or even more depending just HOW wet it is.

 

[huffdawg]

Hi
I am not sure what you mean by is the ground dry?
We live in the bottom of an old glacier formed lake,300+ ft of clay.

Mine is on top of clay also, the 3 ft of fill on top I think gets quite saturated during wet spells.. I guess I won’t know what the problem is till I dig it up .

 

[salecker]

Mine is on top of clay also, the 3 ft of fill on top I think gets quite saturated during wet spells.. I guess I won’t know what the problem is till I dig it up .

All clay here.
Some people make the mistake of digging a basement here and back filling with gravel.Then wonder why they have a leaky basement.I back filled my trenches with dry clay and my basement.