Recently a friend who does HVAC contracting (he lives several states away, so he can't contract for me) noted a heating upgrade could get me a more cost effective system. In addition to the straight oil boiler replacement (we have a cast iron oil boiler right now) he recommended an Econoburn unit (they're made close to us, so shipping costs are fairly low, and he likes their quality). I spoke to him and a representative at Econoburn, and read some things here, and now I'm just confused, so I want to toss out a couple of questions to the crowd here.
First, the rep indicated that due to the efficiency of the gasification process, idle losses are fairly minimal, and their system doesn't benefit a lot from a storage tank. At the same time, my friend indicated that a storage tank would allow for more efficient use of the wood. My friend also indicated that I'd be looking at filling it 2-3 times per day in the winter.
Now, for some math. Our current boiler is fairly inefficient, though we keep our heat turned fairly low in the winter (62F at night, 65F daytime upstairs 68F daytime downstairs) With that, we used 780 gallons of oil over the worst 12 month period. Presuming the wood gasification boiler is no less efficient than our old oil boiler, and using the btu chart at their faq I see that I need 4.9 cords of wood per year. (780 * 138,690 / 22,000,000) Presuming a simple case where I need 4 of those cords over the worst 4 months of the year, that's 1 cord per month. A cord is 128 cu ft round (unsplit), and contains only about 74-86 cu ft of solid wood, split & well stacked. That's an average of 4.3 cu ft round wood per day (or 2.7 cu ft of solid wood mass). The unit sized for my needs (EBW-150) has 6.19 cu ft of space in the firebox.
So here's what I don't understand, with the exception of a very few particularly harsh days, why would I need to load the firebox more than once per day? Surely 2.7 cu ft of solid wood mass can fit within 6 cu ft of firebox, even loosely arranged. If I do need to load it twice per day on average over the 4 coldest months, does that mean I'll be using closer to 8 or 10 cords per year?
Secondly, if I were to get a storage tank, how would that help? If losses to idling are less than 30% (and even if they're bad, I can't imagine they're that bad, I'm talking cool weather, where the heat is demanded every few hours, not summer) then that still wouldn't be able to load only once in one day on average. I might have 24 hours of heating time available in the storage tank, but I'm still going to have to load it twice per day. Those two times can just be at my convenience, instead of when the unit runs low.
Is there something I'm missing? Are losses to idling truly that bad? Or does one fill substantially less than the capacity of the firebox? Or are there far fewer two-refill days than I've come to understand?
I'd certainly like to have a system with a storage tank, I just don't think I can afford that at day one. I'd like to put in a system and save the difference in fuel costs for a few years and then invest that into a storage tank later. I'm already going to have enough work to do erecting an outbuilding to house the system, and leave suitable space for a storage tank at a later date.
Is there perhaps a different unit sized so that I can fill it only once daily for my heating needs?
First, the rep indicated that due to the efficiency of the gasification process, idle losses are fairly minimal, and their system doesn't benefit a lot from a storage tank. At the same time, my friend indicated that a storage tank would allow for more efficient use of the wood. My friend also indicated that I'd be looking at filling it 2-3 times per day in the winter.
Now, for some math. Our current boiler is fairly inefficient, though we keep our heat turned fairly low in the winter (62F at night, 65F daytime upstairs 68F daytime downstairs) With that, we used 780 gallons of oil over the worst 12 month period. Presuming the wood gasification boiler is no less efficient than our old oil boiler, and using the btu chart at their faq I see that I need 4.9 cords of wood per year. (780 * 138,690 / 22,000,000) Presuming a simple case where I need 4 of those cords over the worst 4 months of the year, that's 1 cord per month. A cord is 128 cu ft round (unsplit), and contains only about 74-86 cu ft of solid wood, split & well stacked. That's an average of 4.3 cu ft round wood per day (or 2.7 cu ft of solid wood mass). The unit sized for my needs (EBW-150) has 6.19 cu ft of space in the firebox.
So here's what I don't understand, with the exception of a very few particularly harsh days, why would I need to load the firebox more than once per day? Surely 2.7 cu ft of solid wood mass can fit within 6 cu ft of firebox, even loosely arranged. If I do need to load it twice per day on average over the 4 coldest months, does that mean I'll be using closer to 8 or 10 cords per year?
Secondly, if I were to get a storage tank, how would that help? If losses to idling are less than 30% (and even if they're bad, I can't imagine they're that bad, I'm talking cool weather, where the heat is demanded every few hours, not summer) then that still wouldn't be able to load only once in one day on average. I might have 24 hours of heating time available in the storage tank, but I'm still going to have to load it twice per day. Those two times can just be at my convenience, instead of when the unit runs low.
Is there something I'm missing? Are losses to idling truly that bad? Or does one fill substantially less than the capacity of the firebox? Or are there far fewer two-refill days than I've come to understand?
I'd certainly like to have a system with a storage tank, I just don't think I can afford that at day one. I'd like to put in a system and save the difference in fuel costs for a few years and then invest that into a storage tank later. I'm already going to have enough work to do erecting an outbuilding to house the system, and leave suitable space for a storage tank at a later date.
Is there perhaps a different unit sized so that I can fill it only once daily for my heating needs?
