Interesting results of adding Storage

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

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

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

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