I'm no expert nor do I own an OWB but I think some are missing the point of having a large amount of storage. Once the large mass of water is up to temperature, you don't have to heat it from ambient temperature back to 165-180. All you are doing is making up the difference from what btu's you have extracted to heat with. If you have say 1000 gallons of water in a well insulated tank and it is at 170 degrees and you draw it down to 160 degrees you only have to heat it back up to 170. More storage will mean that you can draw off that storage for a longer period of time. If everything works as it should you shouldn't need to have a continuous burn but rather a burn when needed to raise the storage temp back up.
just my .02
dave
Again I say "google Garn".
taken from the garn website: When the GARN WHS unit drops below the operating temperature of your system, start a fire and heat the water again.
Dave, your right on saying:
"If you have say 1000 gallons of water in a well insulated tank and it is at 170 degrees and you draw it down to 160 degrees you only have to heat it back up to 170. More storage will mean that you can draw off that storage for a longer period of time. If everything works as it should you shouldn't need to have a continuous burn but rather a burn when needed to raise the storage temp back up."
I always fire my stove to 195 degrees and then let it go out. Here in NC it's not as cold as it is up north. I fire it hard then let it go out at night then in the morning it's down to maybe 160 then I put some good seasoned wood in, throw alittle diesel fuel, light it up and turn on the fan and make it burn as hard as I can back up to 190. By the time it recovers to 190 there is nothing but good hot coals, no smoke.You be surprise how long a box of hot coals will keep the water up there. When you have more water storage you can play around with the firing.
Thank you dave_dj1 and NR wooduser for further proofing what I have stated, wherein working
with more water/thermal mass/firebrick allows for more heat transfer and easier firing to maintain
the water temprature desired as you are only heating it enought to bring it back up to the desired
temperature.