I'm planning to add an outdoor gasification boiler to my existing radiant floor heating system. The boiler as well as a ~500 gallon thermal storage tank will be open/non-pressurized. I was planning to use a coil in tank heat exchanger (large coil of copper near the top of tank) to get heat from the storage tank into the closed/pressurized heating system. In this configuration the load could never pull heat directly from the boiler, it will only work after the boiler has brought the tank up to a usable temperature. My concern is that the first 4-6 hours of firing will be used just to bring the tank temp up with no heat output to the load. I guess this is just a problem for the first firing of the season and I shouldn't be concerned about it? Is there a better way to implement unpressurized storage with a pressurized heating system? I'm not opposed to using plate heat exhangers. I'm looking for any suggestions to improve performance and/or efficiency.
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OWB with open storage, draw from boiler?
- Thread starter Rockcrawl
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Most OWB are not designed to use storage. What did the OWB manufacturer say when you asked them about adding storage? My OWB's runs great without it, and I use very little wood. I'd spend the money on good underground piping, lots of ball valves, and a Grundfos pump.
I have a unpressurized system and in the storage tank there is a baffle that traps the hot water from the rest of the tank and gives heat to the heat exchanger within a half hour of firing the boiler !
I haven't purchased a boiler or chosen a manufacturer yet, just planning.
I've been reading a lot about the European method of batch burning, I think this is better suited to my situation vs burning on demand and idling. My heating load is quite low, even a small wood boiler will spend a lot of time idling. I'm afraid it will idle long enough between firings that it will require constant relighting. I'd rather load and light once per day or perhaps every second or third day in the swing seasons, burn hot and continuous, and store the heat. It seems like everyone who has a wood boiler with storage only seems to want more storage capacity.
hobbyheater, I'd like to see a drawing or diagram of your tank if possible.
I've been reading a lot about the European method of batch burning, I think this is better suited to my situation vs burning on demand and idling. My heating load is quite low, even a small wood boiler will spend a lot of time idling. I'm afraid it will idle long enough between firings that it will require constant relighting. I'd rather load and light once per day or perhaps every second or third day in the swing seasons, burn hot and continuous, and store the heat. It seems like everyone who has a wood boiler with storage only seems to want more storage capacity.
hobbyheater, I'd like to see a drawing or diagram of your tank if possible.
You are better off with a European batch boiler that's built to do that vs an OWB. An OWB isn't built to do batch burning.
If the heating load is quite low, why spend 20k on a good OWB? I'd invest in a mini split, and a high-quality wood stove or a good furnace and call it a day.
If the heating load is quite low, why spend 20k on a good OWB? I'd invest in a mini split, and a high-quality wood stove or a good furnace and call it a day.
I was basing my design on the AO Smith and Lochinvar diagrams that show the hot water from the boiler entering the storage tank at or near the bottom on tanks that do not contain baffles. They are intentionally mixing incoming hot water with cooler water in the bottom of the tank. It creates natural circulation, disrupts stratification layers and eliminates the thermocline. Perhaps this is good for DHW supply, but it seems like it's not the best for space heating storage. I see some other diagrams now where the hot water from the boiler enters the top of the storage tank and return water to the boiler is drawn from the bottom. This would eliminate my concerns as the top portion of the tank should heat quite quickly.
I personally think that an old school OWB could work very well doing batch burns...lots of efficiency to be gained there IMO.
The one thing I'd worry about would be heat cycling of the OWB steel...but as long as you keep circulating through the OWB (keep it warm) I don't think there'd be an issue.
But, constantly doing "cold starts" on a gasser would be a real PITA, unless you can keep a good pile of coals somehow...so I guess ultimately, I hafta agree with @sloeffle , no need to reinvent the wheel, a well-designed gasser OWB works fine without additional storage, not sure there is much, if anything to be gained there.
The one thing I'd worry about would be heat cycling of the OWB steel...but as long as you keep circulating through the OWB (keep it warm) I don't think there'd be an issue.
But, constantly doing "cold starts" on a gasser would be a real PITA, unless you can keep a good pile of coals somehow...so I guess ultimately, I hafta agree with @sloeffle , no need to reinvent the wheel, a well-designed gasser OWB works fine without additional storage, not sure there is much, if anything to be gained there.
I have two buildings to heat, home and shop. Both have radiant floors and oil burners. The oil burners are firing at about 50-60k BTUH each, so combined I guess it's a considerable load, but still smaller than most residences in the area. The house already has mini split, I use it for A/C, but very rarely for heat. After living with radiant floors for 25 years I don't want hot air blowing around. I don't want wood/ash/smoke inside the house, nor do I have room to install a wood stove or furnace inside. I have more wood than I could ever use, I'm already using time and energy to move it, I might as well get some heat out of it instead of giving it away. I've debated about installing a wood boiler for many years. The existing system is already set up for an alternate heat source. Tekmar controls, piping, pumps, everything already in place including the insulated underground piping. I won't be spending $20k on a boiler, there are many used boilers available in my area, both conventional and gassers, in the $1000-5000 range. Repairing a used boiler is not a concern, I am a welder/fabricator and I have the time to put into a complete overhaul or rebuild if necessary.
If additional storage isn't beneficial that's great, I'll just run the boiler through a plate heat exchanger.
That's pretty small really...back in the 80's it was super common to have 120k btu oil burners...just your average size house.
The lesson there is that you won't need a huge boiler...but if you get a conventional, they are less picky, but oversizing them still means smoldering/smoking all the time, and on a gasser, oversizing too much is not good, they like to run hard.
I'd have to think anything much under $3-4k is gonna be pretty used up.
Your statement isn't exactly true
OWB is a term being used to lump them all together
I have an OWB which is a gasification unit and is also pressurized.
"Boiler "also used to define that it was a pressurized system
Plus i don't see why any boiler or unpressurized water heater couldn't be used for batch burning.I feel that any wood burning water heater would benefit from running storage, as it almost completely eliminates idling which is the part of the burn which produces the most creosote.
Restarting my gasser is no problem, i have never had a fire not start.
I am kinda lazy though, i fill the burning chamber right full when i start my daily fire.
If i did a small hot fire i would be burning even more efficiently.
But i stuff it full light it wait about 10 minutes close the bypass and return in about 2 hours to fill it again.
Sometimes with a full box after burning for a bit the load will hang up and smoke for a bit, that is where the small hot fire to get a bed of coals before the full load would improve the efficancy
But having an oversized gasser with storage just means you don't have to burn as often if you have lots of storage.
With storage you are hard pressed to oversize a boiler as it's only job is to fill storage with BTU's. It will run wide open in the sweet spot till storage is full.
I would assume any used boiler I get will need work. I'm not sure what gets "used up" in a boiler. Worst case I can imagine is a rusted out firebox or water jacket, which for me is a pretty easy fix. $10-15k goes a long way in repairs, and I actually enjoy restoring things.
This is the same conclusion I've come to which is why I planned for storage.
My thoughts exactly.
Used up, worn out, junk.
Me too...but continually fixing pin holes in the machine that is supposed to be keeping your house warm does not sound like a good time, at all!
Used up? Refractory burnt out needs replacing , components not available and impossible to make without proper molds !
An OWB (Heatmaster, Crown, etc etc) is a unit that's designed to sit outside in the elements. An IWB (Frolong, Vedolux, etc etc) is a unit that's designed to sit inside, hence that's why it's called a IWB, not an OWB. I've yet to see any European type of batch boilers that are designed to sit outside. If they are out there, they are few and far between. Whether they are pressurized or unpressurized doesn't matter.
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My Econoburn was designed to be outside, exact same unit as an inside one except for insulation and a bigger tin box. Pressurized units in both cases, so it is an OWB and an IWB.
Thats what i mean about terms not being used properly
When i started down the hydronic heating road, boilers were pressurized. IAnd i will assume that is still the case.
But terms, names always change in different regions of the country or even country's
Pressurized and unpressurized matters a lot, it defines two completely different heating systems.
So as far as most professionals go a boiler is a pressurized heating unit however it makes BTU's
An unpressurized wood burner is not a boiler by technical terms, but everyone uses the term for their unpressurized wood burners.
The confusion is real, and continues to be pushed by those that are not in the heating profession
True...its a wood fired hydronic heater...indoor, or outdoor, depending on design. HeatMaster is the only one that I'm aware of that has their OWB certified to be placed indoor too.
Think you are spliitting hairs at this point. My OWB is in a building, it doesn't make an IWB, it's UL compliant OWB that happens to be in a building. Again it doesn't matter if the IWB is pressurized or not, it's still an IWB. An OWB is still an OWB if it's pressurized or not. A calico cat is still a cat, a spotted dog is still a dog.
No i am not splitting hairs
A boiler by definition is a pressurized unit,that is a fact.
It doesn't matter how you feel, or how many times you say otherwise the facts don't change !
I too have an actual OWB, a pressurized one that i installed inside a building with storage
Now if the B in your OWB, or IWB stood for burner, instead of boiler then your statement would be true. At the moment your statements
I’ll stop rail roading this thread after this reply.
What’s a Garn considered then?
What’s a Garn considered then?
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A Garn is a wood fired hydronic heater...
Unpressurized, burns wood to heat water, made to be installed in a building.
Could be outdoors with a weatherproof cover with some modifications.
Unpressurized, burns wood to heat water, made to be installed in a building.
Could be outdoors with a weatherproof cover with some modifications.
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