Any tips to hook Buderus wood boiler in series w/ Maxim corn boiler ??

[700renegade]

OK here is my setup. I have a 2 year old Central Boiler Maxim in an unheated pole shed about 200' from the house. The great thing about the Maxim is everything is automated, including my 4" auger feed from a 15T grain tank.

Recently I came across a lot that needed to be cleared of about 40 cords of Oak and Hickory, so I've got 'free' wood piled up high behind the barns. In order to find an economical way to use this wood up, I bought a used ( 2 years ) Buderus indoor wood boiler off Craigslist. This unit is insulated well enough that I shouldn't have much loss in my cold shed. Although the firebox is nothing like an OWB, this unit is rated at 145,000 BTU and will take 27" long wood.

The Buderus is a German made cast iron system w/ wet grates and fairly sophisticated looking HX area - they claim 75% to 81% efficiency and by the looks of things is ought to be better than most any OWB. It is intended to be a pressurized ( 44 psi max ) system.

My intent is to pop the Buderus in the same shed, run my pex return line first thru the Buderus, then the outlet from that to the inlet of the Maxim. The Buderus will sit about 18" lower than the top of the Maxim so it should always be a flooded water jacket. I'll run wood w/ a low maximum damper setting in hopes of getting an 8 hr burn so I'm not relighting all the time. If I set the damper of the wood boiler for 180* and the corn boiler at 170*, the wood should work as primary and corn as 'backup' heat source.

Here are my questions:
> do you think I'll have any corrosion issues w/ the Buderus since it will be running in an open system, not pressurized?

> will 180* water be a problem for the Buderus?

> if the fire is out in the Buderus, how much heat loss will go up it's stack due to the hot water from the Maxim circulating thru it in series?

> is there any risk of it freezing somehow in a 'dead spot' of the water jacket if it is unlit for a number of days?

> any guess on how many hrs burn time I might get on a load of wood.

> an other problems I haven't contemplated?

 

[Hydronics]

>Your questions:
My Replys
> do you think I’ll have any corrosion issues w/ the Buderus since it will be running in an open system, not pressurized?
It's less than ideal, are you treating your existing water? Have you checked the PH/reserve alkalinity? It will corrode to some extent but will probably outlast the steel boiler under the same conditions.

> will 180* water be a problem for the Buderus?
My old boiler is a Buderus, they are tough units and in my opinion the Cadillac of updrafts. You can run it at 200, they actually recommend 190 to reduce creosote. They're great for burning anthracite coal. I may keep mine in case I decide to do this in the future.

> if the fire is out in the Buderus, how much heat loss will go up it’s stack due to the hot water from the Maxim circulating thru it in series?
I'd put it in a small enclosure.

> is there any risk of it freezing somehow in a ‘dead spot’ of the water jacket if it is unlit for a number of days?
You should be ok as lond as you're constantly flowing through it. Enclosure.

> any guess on how many hrs burn time I might get on a load of wood.
I got about 8 hrs, depends on heat load though.

> an other problems I haven’t contemplated? Again, put it in an enclosure.

 

[jpowell1979]

I personally like primary/ secondary plumbing for dual fired installations. Either system can add heat when it is available and it is easy to isolate either system for maintenance.

 

[700renegade]

Hydronics, I'm running stock Central Boiler corrosion inhibitor. Why do you suggest the enclosure? Do you think the 3" fiberglass insulation blanket around this unit is going to have significant heat loss? I can't imagine it's any worse than the insulation my neighbor's Aqua-therm OWB.

Another question: Since I'm at atmospheric pressure, if I get a good fire going is there any chance I'd get the Buderus above boiling and be burping steam into the backside of my Maxim corn boiler?

 

[Hydronics]

Hydronics, I'm running stock Central Boiler corrosion inhibitor. Why do you suggest the enclosure? Do you think the 3" fiberglass insulation blanket around this unit is going to have significant heat loss? I can't imagine it's any worse than the insulation my neighbor's Aqua-therm OWB.

Another question: Since I'm at atmospheric pressure, if I get a good fire going is there any chance I'd get the Buderus above boiling and be burping steam into the backside of my Maxim corn boiler?

The greatest heat loss will be from the back at the smoke hood area and the bottom. I wouldn't necessarily use an OWB as a good design example.

As you know water boils @ 212 @ sea level, higher elev. lower temp. Suction from a circ. will lower the pressure worsening the condition, be sure to keep your circ. on the return to the boiler. Circ. cavitation is more likely to be an issue especially if you have a high head circ. & small tubing. Cavitation beats up the circs. impeller.

You could pressurize it, add glycol & a hx, starts to add cost though.

 

[700renegade]

My current circ pump ( tayco 009 ) is on my Maxim corn boiler on the discharge line, so cavitation isn't a factor here ( flooded inlet on the pump ).

I thought about running this with a hx and under pressure, then I could gycol the Buderus system ( it only holds 10 gallons ). My preference is the KISS approach of inserting it in series. If I have a fire in the Buderus a high percentage of the time, 'parasitic' heat loss should be no concern.

In a few years I may move these boilers into a new heated workshop and the heat loss off the units themselves won't matter.

Anyone have a guess on the real world efficiency of the Buderus I bought and how it compares to a typical OWB?

 

[harttj]

If you do this, post the corn consumption of the Maxim idling all day. I'd be interested in seeing what the usage is.

Tim

 

[fratelli101]

HI,thanks for the ideas. Will definitely try one of these. THen i'll post here my feedbacks...


Regards,
fratelli101
(broken link removed)