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[Sprinter]

Fact, boilers are at their least efficiency while idling. The best OWB's also have the largest volume or storage of water.  Any boiler system will see a net gain by adding any amount of storage, if installed correctly. Anytime you increase the gasification burn time, you increase the total efficiency. Who would run a delta T of 50 on storage. One giant loop hitting 2-4 exchangers is not correct. Even those mod cons use buffer tanks to increase efficiency.
I don't know about that math, but if a 125kbtu  tiny boiler can recover heat for 1500-2000 gallons and not fire for 2 days while heating 3500sqft, I think a larger boiler with more mass can also. Both being gassifiers. Some are getting more days. You have to think of your storage as you trucks gas tank, you don't have to top it off to operate. And with outdoor reset controls and the Taco electronic ODR or set point mixing valves you can see a week easy without firing. Over in Europe its illegal to idle, and the boiler controls don't even have that option, over here at least you can. If you understand how a buffer tank or hydraulic separator works then you can see how you can recover storage and cover a heat demand at the same time.
Proper placement and control of BTU's make a system efficient. My storage tank looses 1/2 degree per hour or 12 degrees per day. With the cover its 7/day. Most of it is thru the pipes themselves that don't have gravity loops.

[netwerx-r-us]

Slim , Dairy country , no , I'm about 60 miles west of Nashville tn , Its 19 degrees now , 2 large greenhouses are very inefficient to heat , I keep them at 55 and 60 degrees each , I get about a 6-7 hour burn time when its this cold , the greenhouses do heat up during the day simply from the sun but have no way of storing that heat gain , Scott's post made sense , it can be done but if after you get that much water to temp if you let it go down it will be a hard time keeping up, I see that with my 300 gallons , i can only imagine with an additional 500-1000 gallons tied to it .

I think I will look at using the sun with some homemade solar collectors and a water storage tank underground in the greenhouse , after a bit of research I see  dairy tanks and even propane tanks being used , I think ill build me a tank below grade and insulated to give it a whirl, like everything else I have 15 projects going on at same time



 

[slimjim]

Netwerx, another good place to look for tanks is retired fire trucks, the tanks are normally plastic and almost never re-used, think about bench heating at night off the tanks, alot less heat loss and the plants won't know the difference!

[Scott7m]

Fact, boilers are at their least efficiency while idling. The best OWB's also have the largest volume or storage of water.  Any boiler system will see a net gain by adding any amount of storage, if installed correctly. Anytime you increase the gasification burn time, you increase the total efficiency. Who would run a delta T of 50 on storage. One giant loop hitting 2-4 exchangers is not correct. Even those mod cons use buffer tanks to increase efficiency.
I don't know about that math, but if a 125kbtu  tiny boiler can recover heat for 1500-2000 gallons and not fire for 2 days while heating 3500sqft, I think a larger boiler with more mass can also. Both being gassifiers. Some are getting more days. You have to think of your storage as you trucks gas tank, you don't have to top it off to operate. And with outdoor reset controls and the Taco electronic ODR or set point mixing valves you can see a week easy without firing. Over in Europe its illegal to idle, and the boiler controls don't even have that option, over here at least you can. If you understand how a buffer tank or hydraulic separator works then you can see how you can recover storage and cover a heat demand at the same time
Proper placement and control of BTU's make a system efficient. My storage tank looses 1/2 degree per hour or 12 degrees per day. With the cover its 7/day. Most of it is thru the pipes themselves that don't have gravity loops.

not quite sure what your reffering to as a delta t, shew.  Im talking available affect heating temp of water not difference in supply and return

No one is arguing that a long burn time is less efficient, but to think you can take a conventional stove or even a gasser not designed for storage and add storage and suddenly heat for days per fill isnt true either.   The math is where its at, there is only so much usuable heat in 2000 gallons of water.  I was simply saying if it cools to 150 from 200, thats  still 830k btu of available heat.  So if your heat load is normal for most folks lets say 45kbtu per hour, just divide 830/45 and you have how many hours it will do its job.

Once again, I know the European style mass storage boilers who do batch burns are very efficient, but in an outdoor wood boiler forum its not practical or a good idea to lead people to believe the answer to there efficiency is nore storage.  Best advice is for everyone to install there stoves aa close to dealer specs as you can, it was designed that way for a reason

[Sprinter]

A boiler is a boiler, regardless of fuel or efficiency in burn or transfer. Any storage, be it buffer tank or storage tank is exactly like a battery. Delta T, well you don't run a battery dead before you recharge, and that's what you'd be doing by having a big delta T in tank temps. All these OWB's already are fed multiple times a day.  So while tending why not run at max efficiency to recharge. So if it takes a solid 2-6 hours of full gasification (a stoves most efficient use of wood) to recharge storage it reduces cycle times. Just with any boiler the more you reduce cycling the more efficiency you get out of the boiler and fuel.
Even something as small as a 30 gallon buffer tank will help. A lot of the problem lies with typical bad manufacture design and suggested install. Just like the diagram where you see everything connected in one big loop and an oversized pump on too small of a supply line running 24/7. There is nothing efficient about a wood eating design like that.
2000 gal is a lot and that's why there's design sizing programs to fit the bill. But as the industry likes to do, bigger must always be better.
So when a OWB is flowing 8gpm thru 1" on a call, but only the baseboard or air handler is calling for 30-50kbtu or 3-5gpm flow,  the buffer or storage tank would store the excess. Every so many calls the boiler wouldn't even have to fire. saving fuel and electricity from a proper design and placement of btu. Buffers and storage are a proven design in hydronic heating, utilized by the most efficient systems. The heating source does NOT matter. The OWB industry itself makes its own bad name, by letting butchers install their product. This does not apply to all manufacturers and installers. I am sure you yourself have taken some bad installs and made a very good system out of it. Half or more of the ones I work on, are flat out jokes. Where they sold him the cheapest package to make the sale, rather than doing a proper sized design, of course it cost more to do it right. Pay a little now or pay a lot later. Unfortunately it's the customer that suffers. Zoning, buffer, correct circs and supply line size and quality are where most problems lie.  It is easily possible to cut wood usage by 20% Really bad ones can cut the wood in half. 1% of the time an OWB installer supplies the customer with a manual J.
The only way a buffer or storage would not benefit a system is if the output perfectly matched the load on every call for heat. An impossible feat for even the most flexible and efficient systems, when the correct design is sized for the coldest day.

In your opinion what percentage of OWB installs are done correct? Doesn't have to the best, just working properly

[Sprinter]

1820 sq/ft house up in Almont, plus the man cave poker room / shop office. OWB rated at 120kbtu/hr max , 1000 gal LP tank feeding the primary loop thru a hydraulic separator and a taco i125T4R-1 mixing valve that feeds baseboard zones ,infloor tile heat and IDWH in the house. He burns from 6 to 7-7:30 charging the storage, while guys show up for work and getting the tree trucks warmed up.  Then again in the evening for an hour to 2 hours charging the storage.  That's it , no feeding during the day or late into the night, when it's above 25 degrees for the day it only takes a 40 minute burn to recover.  The house heat loss is 39,000. The shop office Its 11x 22' corner section of the barn not heated at night unless we're playing poker.
Prior to the storage, added pex lines and ODR mixing valve it burned or idled 24/7 and had to be fed minimum 3 times/day packed and praying for no bridging. It doesn't have to be packed full and it only burns hot, no low return temp worries. The fire box is much cleaner from the hot burns.