captonion said:
I must be a slow learner!
Longer time between feedings means less wood used. No?
My thought are that if well insulated storage is used there will be less heat loss as the water cycles if there is 500 gallons as opposed to 50. I may be wrong, thats why I ask.
You need to make a bigger fire(and thus probably have a bigger boiler), and therefore use more wood to get the same amount of BTUs out, then save them for later.
Let's break it down. I'll make up some numbers here.
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Scenario 1, no storage:
Your heat loss is 50,000 btu/hr
You have a 55,000 btu/hr boiler
You will need to keep the boiler cranking nearly 100% of the time, but you will put 4 splits in on each reload, every 4-5 hours(assume this as being a "full" boiler load). You need to keep the boiler loaded, and every 4 hours turns out to be loading 6 times a day.
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Scenario 1, with storage:
your heat loss is 50,000 btu/hr
you have a 55, 000 btu/ hr boiler
You still need to keep the boiler cranking most of the time. Every once in a while on warmer days, some heat goes into the storage, but the house is constantly calling for heat, and the storage never really gets to temp.
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Scenario 2, no storage:
your heat loss is 50,000 btu/hr
you have a 100,000 btu/ hr boiler
You put 8 splits in the boiler, it runs for about 3 hours, then idles, and kicks on again after 2 hours. during this idle time, the boiler is still consuming wood,(albeit slowly, it's still going) and is also making smoke and possible creosote buildup. The boiler runs out of wood after 5-6 hours, and abruptly stops heating the house. The wood
sorta lasts longer, but you're consuming wood and not gaining any energy out of it during the times that its idling, and, just like the above "no storage" option, as soon as the wood runs out, it stops heating abruptly. THIS is the only scenario where adding storage will save wood consumption.
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Scenario 2, with storage:
your heat loss is 50,000 btu/hr
you have a 100,000 btu/ hr boiler
You put 8 splits in the boiler, it runs for about 2 hours, then the house stops calling for heat. The boiler still has a pretty decent fuel charge, and starts putting the energy into storage instead of idling. Once the house calls for heat again, the boiler stops charging the tank and starts putting heat into the house. You can now let the boiler burn all its fuel, and continue to heat the house from storage. Depending on the amount of storage, or how you want to run your schedule, you can run the boiler for 4 hours, then go another 8 hours just running heat from storage. This allows you to put 8 splits every 12 hours, instead of 4 splits every 4 hours. It's the same amount of wood, but a much easier schedule to maintain.
It's not quite that simple, because while the tank is charging the house will still call for 50,000 btus every hour, but this is a decently accurate model. I hope you can now see why the storage doesn't reduce wood consumption, unless the boiler is oversized and idling.