DREAM BUILD

[STANG302]

Gooserider

Thanks, those are answers I've been looking for.

I agree with you on the pellet boilers. They are able to react when heat is needed or not. So storage may or may not help much. My theory on using storage with a pellet boiler is mainly to use less pellets. If I could cut it down from say 5 tons to 2 tons of pellets a year. Thats a win to me.

Your also right on the septic tanks. They need to be buried for structural support. I have a vision in my head of burying a tank or two undr the slab. With the man hole covers flush with cement pad. But sealing and insulating the tanks being used in this fashion has some challenges. I still have time to put together solid plan on what I'm going to do. So more research the better and we'll see what I can come up with.

 

[pybyr]

Gooserider

Thanks, those are answers I've been looking for.

I agree with you on the pellet boilers. They are able to react when heat is needed or not. So storage may or may not help much. My theory on using storage with a pellet boiler is mainly to use less pellets. If I could cut it down from say 5 tons to 2 tons of pellets a year. Thats a win to me.

Your also right on the septic tanks. They need to be buried for structural support. I have a vision in my head of burying a tank or two undr the slab. With the man hole covers flush with cement pad. But sealing and insulating the tanks being used in this fashion has some challenges. I still have time to put together solid plan on what I'm going to do. So more research the better and we'll see what I can come up with.

Back in the early '00s, I seriously looked into retrofitting my existing furnace with one of the pellet-burner heads such as are widely used in Europe and are just now becoming more widely available in the US-- they bolt up to replace the "oil gun" assembly. During the oil-price run ups in the last few years, I am glad that I did not bank on pellets-- as, being a commodity, they followed oil prices upward. If you can cut your own wood, you can be your own cartel, and not dependent on another.

 

[Gooserider]

Gooserider

Thanks, those are answers I've been looking for.

I agree with you on the pellet boilers. They are able to react when heat is needed or not. So storage may or may not help much. My theory on using storage with a pellet boiler is mainly to use less pellets. If I could cut it down from say 5 tons to 2 tons of pellets a year. Thats a win to me.

Your also right on the septic tanks. They need to be buried for structural support. I have a vision in my head of burying a tank or two undr the slab. With the man hole covers flush with cement pad. But sealing and insulating the tanks being used in this fashion has some challenges. I still have time to put together solid plan on what I'm going to do. So more research the better and we'll see what I can come up with.

Storage will NOT improve your pellet consumption, other than possibly during the shoulder season if you have times when your house load is less than the pellet boiler's minimum output. In that case, the storage will work the same way it would for a cordwood burner, but presumably you would want a LOT less storage, as you'd just need enough to store the surplus heat output at the lowest burn rate, and give a reasonable cycle time... I would guess that at most you'd want maybe a couple hundred gallons, likely less...

I would also second pybyr's comments on pellet pricing... Pellets are handy and convenient, but they are NOT cheap, and IMHO aren't all that "green" considering the amount of energy that goes into their production and transport... I'm also not real comfortable with the idea of a system that is so dependent on such a specialized and dedicated fuel. (Note past shortages of pellets in different areas) Not saying you can't do pellets if you want to, but just that IMHO it isn't a great choice...

Gooserider

 

[Jim K in PA]

Trevor and Goose are spot on. "Convenient" and "easy" have a price. Only you can determine if that price is worthwhile.

In addition to cost, the other factors to consider when comparing external storage vs integrated storage is heat transfer efficiency and control/piping complexity. There are no 100% efficient water:water heat exchangers that I am aware of. The GARN has all of it's heat exchanger piping as well as the fire box and SRC located within the storage water. Whatever heat can go into the water, will. As to controls, you will want to heat your house first, and then your storage, with a divorced system. Many others here on Hearth have done this successfully, it just takes planning.

 

[STANG302]

Please help me understand why storage on a corn/pellet burner has no benifits. How would it not reduce fuel usage?

 

[pybyr]

Please help me understand why storage on a corn/pellet burner has no benifits. How would it not reduce fuel usage?

Fossil fuel boilers never used storage because you can modulate the output (on/off) quickly and easily with rather little penalty in efficiency.

Wood boilers benefit from storage because it takes planning and effort to light a wood fire, and once lit, you can't really 'turn it off' on short notice; you can damp the fire down by starving it for air, but then your efficiency goes to heck, as you're running a smoldery fire. Storage lets you run a clean/ hot/ fast wood fire, and "bank" the BTUs for later and more gradual use in response to heating needs.

Pellet (and shelled corn) devices are capable of turning on/ off rather easily in response to heat demands.

The laws of thermodymamics mean that you can't avoid some losses when you convert/ transfer/ store heat.

With wood, the gain in burn efficiency more than offsets the losses in transfer/ storage.

With any fuel that you can turn on/ off, you might as well have the "storage" in the unburned fuel, waiting to be used until there is a call for heat.

 

[sdrobertson]

Please help me understand why storage on a corn/pellet burner has no benifits. How would it not reduce fuel usage?

Corn/pellet burner are about as close to a fossil fuel burner as it gets. When you get a call for heat, they will feed in the fuel into a small burning pot until the heat load is satisfied then they slow down till you call for more heat. With cord wood, it's allot harder to "stop the burning" in the middle of the load of wood burning so you need a place to put this heat which is the reason for storage. If you try to stop this burning for extended periods of time the fire still has to smolder which kills some efficiency. What Goose means with it may help a little bit during the shoulder seasons is that you house will need very small amounts of heat which may be larger than the lowest setting on the corn/pellet burner so you could heat the storage and live off that for extended periods so that your burner only burns when it has a larger load needed (i.e. when the storage is cold and the house needs heat) then you'll use all of the heat the corn/pellet burner produces as you'll be heating both.

EDITyrbyr-you're allot faster at typing than I am!

 

[STANG302]

Thanks,

That makes a bit more sence to me.

So far in this process the easiest thing so far is picking a building. Heating it has been, well a learning experiance. Almost to many options and routes to take.

 

[pybyr]

Thanks,

That makes a bit more sence to me.

So far in this process the easiest thing so far is picking a building. Heating it has been, well a learning experiance. Almost to many options and routes to take.

I don't have a Garn, but if I had a "clean slate" like you do, it'd be near the top of my list.

 

[STANG302]

Garn is near the top of my list to. Just looking around at all the options available to me.

One feature that a pellet boiler rears it's ugly head. Is for expansion down the road. If I build a house in 10 years or so. I'd need a seperate heat source.
A garn unit or other type of wood boiler with storage. Would be capable of expansion down the road.

 

[Der Fuirmeister]

Since you are doing in-slab radiant, look at the information of the radiantcompany.com. They recommend a slab insulation plan that leave the center of the slab uninsulated (broken link removed to http://www.radiantcompany.com/details/grade.shtml) Since the perimeter (about 8 feet I think) is insulated, this makes for a HUGE heat sink in the center of the room. At first is seemed strange but after thinking about it the thermodynamics make sense. I used them to size my wood floor radiant system and they were very helpful. I second the suggestion for the loading door in the shop. Stack your firewood on pallets then bring it in to the shop with forks.

I have seen a LOT of discussion on the Radiant Co, and their idea of putting a hole in the insulation - they have a lot of good info on their site, but IMHO the idea of putting a gap in the middle of the floor makes absolutely NO sense for the vast majority of installs - especially those close to rock, or on damp soil - you will NOT get the heat back out that you dump into the ground under all but the rarest of circumstances, so why not keep it in the slab where it belongs? You are right though, it does make a huge heat SINK in the middle of the room - and I don't want to sink my heat or the money and work I use to make it...

Far as I'm concerned, this is another one of those places where the same question Sigienthaler asks about those peddling various "miracle insulation" materials (i.e. "bubble wrap") for underslab applications is appropriate - Namely, if it doesn't work as advertised, will the Radiant Co. come out and pay to fix it? Given that there is no PRACTICAL way to fix a slab, I'd rather spend the extra couple hundred bucks on the foam needed to do the job right...

Gooserider

I haven't been to the radiantcompany web site, however you need to do the math when evaluating any design. We have in floor radiant in our shop. The first year we used the natural gas furnaces to heat which cost $4000. The ceiling air temp was 85 degrees and the floor was 50-55. The shop is kept at 55 degrees air temp minimum (using a simple thermostat) and on occasion we raise it to 60. This year with radiant heat the slab temps run 58 - 60 degrees when the shop is at 55 (again using a simple thermostat). The ceiling temps are also 58 degrees. I used a heat gun to read the temps at the floor and ceiling. I was pleasantly surprised to find out how little the temp difference is from slab to air.

When we built in 2007 we poured the slab on a stone base. We insulated the perimeter with R10 foam on the outside of the foundation wall and inside under the slab. Although the bubble type insulation has been the topic of much debate, we used it because we did the math and determined that we would never see a return in dollars spent if we used rigid foam under the whole slab. This took into account that the system was designed for slab temps 5 - 10 degrees above the ground temps. The R3 bubble foam also had a the advantage of providing a moisture barrier. There is a point of no return when adding dollars for more insulation. The cost to heat with oak cord wood this winter was $500. The added cost to use a higher R value foam in our shop would have been $4000 plus labor. Instead we stuck the money into added ceiling insulation.

I'd suggest adding insulation where it will provide the greatest benefit. If you are insulating to keep 50 degree ground temps away from a 58 degree slab it doesn't require a lot of insulation. There are also some structural concerns with installing rigid foam below a concrete slab. This may not be a factor in a home. Until you sit down with a calculator you'll only be guessing.

Hope this helps.....