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Wood Boilers

Plumdog_2 Member Posts: 873
Anybody tried the shell and tube exchangers that are sold by Central Boiler? They show a vertical install on the side of a standard water heater that utilizes a gravity flow on the potable side of the exchanger. I was wondering how well this works from someone with experience with this setup.


  • hr
    hr Member Posts: 6,106
    They work

    not super fast as they are a thermo siphon on the "B" side. They can also get the tank up to 180° if they are not controlled properly!

    hot rod

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  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,290
    As with many things suggested

    AS with many things suggested by the majority of the O/D boiler companies............Well......Yes, it works, in a roundabout way sorta,........usually, everyday except the 3rd Tuesday of each month............sometimes.

    I've found reading through the manuals for a number of these units, from many different manufacturers, that they try to dumb down the installation as much as possible. I would assume that this is to try and make their product appeal to the DIY folks.

    I came across an installation where the HO had a sidearm type water heater for his domestic hot water. The boiler loop fed through constantly, 24/7. The domestic side was just gravity flowing through the "B" side. His complaint was that sometimes when his wife opened a hot water faucet, steam came out instead of water. He had his aquastat on the O/D unit set at 210* because he had been sold an undersized heat exchanger coil for the heating side of the program.............Go figure.

    Ditto to what HR said!! Proceed with caution.
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    you guys are right

    about the dumbed-down instructions and schematics. They show the heat exchanger piped into the T+P valve port and the T+P is nowhere to be seen-nor is there any mention of an aqaustat. Yikes.
    I knew a carpenter once that built his own heat exchanger inside a woodstove and piped it to some baseboard. He said he was sittin around the stove having a glass of wine and thinking about how great this thing worked when it blew up in his face.
  • Martin Lunde, PE
    Martin Lunde, PE Member Posts: 6
    wood boilers

    The vast majority of outdoor wood boiler manufactures do not have anyone on staff who has studied or really understands heating (delivery systems, pump sizing, building heat loss, etc). For instance, every HWS and HWR pipe is either 3/4" or 1" no matter the load or distance from the wood boiler to the heated building! And if boiler X is the correct size, boiler 2X is even better because it is twice the size!

    At DECTRA (manufacturer and distributor of GARN WHS wood units we have Engineers on staff who have been in the heating design business for 30 years; and we only sell through trained qualified dealers who can properly size equipment, install equipment, trouble shoot systems, etc. Over the years we have replaced many other manufacturers failed outdoor units with ours. During the process we almost always find: oversized wood units, improper pipe sizing, improperly installed pumps, undersized coils with very high air side pressure drops, dismal control, high fuel usage, excessive emissions, etc.

    This idustry begs for technically competent personnel, truth in advertising and a thorough shake out of the players.
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