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Corn burning boiler add on

AHerra Member Posts: 15
Here goes. 8 years ago I converted an old 2 pipe steam system to a hotwater system for a friend of mine. He called the other day and told me he purchased a corn fired boiler and wants to add it for his primary heating system and leave the L.P fired boiler in place for back up. I also plan on adding a DHW for him and his growing family.  I have been contemplating how to pipe and control the boilers.

Here are my thoughts. I was going to take his original piping and make it a loop with a supply pump. Put my closely spaced tees in with 4 sets of tees off the loop tees. #1 for corn boiler #2 LP boiler #3 DHW #4 Heat disipator loop to radiators in basement. Required by corn boiler manufacturer.

I am coming to a loss for controlling all my needs. I don't think I am going to need priority for DHW since there is no way to fire the corn boiler on and off. Its always gonna be on. The disipator loop is controlled from the corn boiler and should be easy. And the second boiler will only need to be fired for DHW in the summer and back up heat. Should I just install a second thermostat on the wall for LP boiler or should I control that with an aquastat.

Anyone have any experience with this set up.




  • Ironman
    Ironman Member Posts: 7,399
    Corn Boiler

    We do alot of outdoor wood boilers that have the corn burner as an option. Do you know the make you're going to install?

    You're right on track with a primary loop and everything feeding on/off it. I would make it primary/secondary series with the corn boiler the first connection, then the gas boiler, then the DHW, then the radiators as you said.

    Put an aquastat on the corn boiler that will bring on its pump when it reaches temp. Leave the rest of the controls just as if the corn boiler didn't exist. You don't want to even consider that second t'stat which the corn boiler manufacturer recommends. You may want to set the high limit on the gas boiler 10 - 15 deg. lower so it doesn't try to fire if corn boiler is hot. Or if you really want to keep the gas boiler off for sure when the corn dog is hot, connect a relay to the normally closed contacts of the aquastat that you'll put on the corn and run the burner from the gas through the relay.

    Also, If the corn boiler is not a pressurized (30psi) vessel, and I'm not aware of any that are, you'll need to put a heat exchanger between it and the house loop with an additional pump on the house side.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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