Interesting results of adding Storage

[Paso]

Well I added 300 gallons of storage this summer and had a test firing last night. Only 20 degrees outside over night.
After 14 hours I had 90* water on all 7 gauges ( gauges spread all over )
Almost a complete burn a few embers still glowing but no reconizable wood.
The storage tank (old HHO tank ) has 3 of the gauges on end wall.
When starting from a cold OWB at one time I had 180* water at top of wood boiler and 80* water on the lower supply outlet.
Here is what I did to add the storage.
The oil burner is in the loop put not fired up yet.

 

[Gooserider]

Where the lines from the oil boiler cross the same color lines to the shop, are there intersections, or just cross-overs?

It's not real clear to me what the flow patterns are, but it really is best if you can set stuff up so that the oil boiler doesn't heat the storage, and that the wood boiler sends its out put heat to the storage tank first, or else set the storage tank up as a zone that can be heated whenever you aren't getting calls from your other loads. It doesn't look like your diagram does either that I can see...

What kind of stratification are you getting in the storage tank? Remember that a tank with very hot water at the top and cold at the bottom is potentially more useful than a tank of warm water that's all the same temperature...

Gooserider

 

[Paso]

The red line from the top of the oil boiler goes to the bottom of the Telydyne box heater that heats the boiler room with heat( 8 x 48 semi trailer) ,the water exits the top of the box heater and flows downward into the top of the storage tank expansion pipe about 12 inches above tank. The bottom far right side of diagram ( blue line ) supplies the oil burner intake.
The water goes from the bottom of the wood boiler directly into the shop and supplys two large bus radiators. when the water returns from the shop it is tee'd into the lower storage tank fitting and the lower wood boiler fitting.
The temperuture in the storage tank varies but is usually 10* from the very bottom to the vary top which is the higher temp.

I have plumbed it this way so I could run either unit to heat the water in the primary loop and get maximum water temperture when needed also freeze protection we often get -40
Since I added the storage and the oil burner boiler I have been just experimenting on how hot I can get the water flowing to the shop ( 10 ft away ) as the two large bus heaters and one 24 x30 heat exchanger pulls the heat out of the lines.

 

[Gooserider]

Definitely not the way I would have plumbed it, but whatever works for you...

Gooserider

 

[Paso]

How would you have plumbed it??

 

[Gooserider]

Well starting out as I mentioned in my first post, I would have set it up so that the oil boiler didn't heat the storage at all, and the wood heater sent its output to the storage tank first, then fed the boiler room heater and shop loads from the storage tank.

I would have done as much as I could to get the storage tank plumbed in a way that minimized mixing and maximized stratification.

If freeze protection was needed, I would have looked at adding a ZV controlled bypass loop into the return from the shop so that water could flow backwards through the storage tank and wood boiler on the way to the oil boiler (remember, these don't need to be kept hot, but only above 40*F or so...)

This way you get the most use out of the storage, and only spend wood and oil heating things that need to be heated, when they need heating...

Hope this makes sense,

Gooserider

 

[Paso]

Okay I get your thinking and somewhat agree however I think my circumstanses differs from the norm. I should have mentioned it earlier.

I ran the wood boiler as a stand alone unit and everything worked satisfactorily. But thats never good enough right

I added the oil boiler to just heat the boiler room and give me the option of heating the system water without personal attendance. ( freeze protection)

I added storage only to see if more warm water capacity circulating would give me more time between wood fillings.

I am heating a 5000 sg ft shop on weekends only ( saturday and sunday ) the balance of the week I just keep the fire going to keep everything circulating and from freezing up.

On friday night I usually start ramping up the fire so that I can pull the maximum heat from the radiators on Saturday morning.

Long term plan is to use this trailer to heat a radiant floor which will be a whole differant story as the requirements will be so much less.

I was just sharing my observations of adding 300 plus gallons to a OWB.

Hope I make sense

 

[Gooserider]

Even with your different circumstances, I'm not sure that I would do anything different from what I suggested... 300 gallons of storage is also not that much, although it might have made a good buffer for the OWB, and given it a longer cycle time between idle and full burn. I don't know that it would have actually given you much more in the way of time between reloads.

Where I suspect you would have gotten the benefit is by reducing the number of times your OWB would have been switching between full bore and idle modes. I am not an expert on OWB operations, but from all the complaints I've heard about them, it seems the big issue is that they make a lot of smoke and are particularly obnoxious when coming off idle and getting the fire hot again. When actually burning hot they supposedly aren't that bad, and they aren't that bad at idle, just during the transition. Without the storage, I would expect that your OWB would cycle on and off quite a bit once the shop got up to temp, and possibly even while it was heating. You might also have been subject to a lot of boiler damaging low return temps during the weekly rewarm of the shop... By using the storage tank as a buffer, your boiler wouldn't see the cold return water as much, and presumably it would spend a lot longer in full burn mode heating the buffer tank, then idle longer as the system heated off the buffer...

Thus I don't know how much you'd get in the way of added time between loads, but I would expect that you might burn each load cleaner with fewer on-off cycles.

Gooserider

 

[Paso]

Yes I think you are right I am getting no on /off cycles. It is burning hot and quick and complete to heat the added water. The real test will be when we get weeks of -30 - -40 weather.

Last winter the unit did have lots of on off cycles and when I came back 12 hours later I had lots of hot coals and a bed of embers that required just adding more wood.

Now I need to start a new fire each time. Last year I started one fire in November and it lasted till march.

Too early to tell which I like better.