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OWB exchange plate location

Ya2UP_A Member Posts: 21
edited October 2023 in Biomass
Good day, I’m looking as to where I can pipe in my outdoor wood boilers exchange plate. I purchased a home with an old Johnson little John and a really old indoor oil burner as a back up in the basment. I’ve since removed the oil fired boiler and installed a wall hung LP combi boiler but left all the wood boiler plumbing intact knowing, I was going to connect them later. That said the combi and piping are crammed into a small 4x4 spot on the wall there was no more room to utilize so the plumbing is tight, the combi is plumbed in a close space T continues loop fashion and there in lies the problem, the way I understand it I must break the return with two T’s running to the plate exchanger in  which I did however sort of, becouse of the compressed area and short pipe allowance, I was not able to put them near each other which is defiantly not working as the plate water is not getting anywhere near the combi boiler. I’m thinking the only way I can add more copper is if I extend the main supply and return coming directly out of the bottom of the combi towards the floor and in doing so put in two more close space T’s on the return side for the plate exchanger. Will this work or am I wasting my time?  The only reason I’m wanting to integrate the old Johnson is to burn through the 16+ cord of wood that was left here by the previous owner. And who knows from there.  I’ve attached pics a drawing of the current situation and a drawing of my potential next move. Please let me know what hall think. Thanks for any advice!  


  • leonz
    leonz Member Posts: 1,187
    I filled my hand fed boiler half full of firebrick up to the flue breech to add thermal mass and I cut my wood and coal use in half.

    Is the existing forest eater a closed system or an open to air system??

    Do you know how often the water in the boiler was tested?

    Do you know when the plate heat exchanger was last cleaned?

    Have you cleaned the existing plate heat exchanger with vinegar to remove any scale?

    What brand of circulator do you have on your forest eater and how old is it?

    Is your hot water circulator in the back of your forest eaters fire box like most of them or in the house by other boiler?

    If the plate heat exchanger for your forest eater is not pushing hot water into your system it may very well be plugged up or the circulator is not pushing water to the home very well and needs to be replaced as the volute in it is worn out.

  • Ya2UP_A
    Ya2UP_A Member Posts: 21
    The unpressurized renewable green energy maker is working just fine, I just completed flushing the lines and test running it, in doing so I flushed the exchange plate with white vinigar and it’s running a modern taco e series. Hot water from the OWB to the inside plate and sidearm DHW is running flawless however getting that plate to play with the combi is the problem here. It’s only about a 3’ span of pipe from the plate to the combi so I don’t think an additional circ pump is the key. Tying in a plate is pretty simple on an older system or one with adequate  space to work with. 
    when cut into the return however I’ve never seen this done with a close space t loop like mine, on all other examples including my last house the plate completed the return circuit.  I guess what I need to figure out is if the old tech will work with the new tech and if so where I can add the new T’s as I don’t think this is plumbed correct. 
  • hot_rod
    hot_rod Member Posts: 22,483
    It comes down to how much control and piping technology you want to throw at it :)

    Piped like this, either or both boilers can add energy.

    With low temperature radiant, run the OWF as low as possible, maybe 90F or lower, if you have slab radiant.

    The delta T controller is watching two temperatures and determines when then OWF is no longer contributing, then turns off that HX circ.

    How is the DHW side arm installed? Sometimes they are in series, always getting flow. Or treat it as another load, with its own circ.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream