Optimum tank size for a Solo 60 just 650 gallons?

[MrEd]

Has anyone noticed the tiny little print in the back of the Tarm manual on the last page - it states that the optimum storage size for a Solo60 is 650 gallons, for a Solo 40 - 600 gallons and for a solo 30 - 400 gallons?

These are a LOT smaller than some of the other numbers I have seen recommended/thrown around.

In any case, for the first year I am sticking with 500 gallons of pressurized.

 

[stee6043]

Everything I've read seems to indicate "more is better". If you have decent stratification there really should be no downside to having more storage. The upside is longer periods without burning (assuming good insulation of the tanks)....of course if your tanks are not insulated well the bigger storage will potentially reduce your overall efficiencey because you're putting more in and getting less out.

 

[pybyr]

Has anyone noticed the tiny little print in the back of the Tarm manual on the last page - it states that the optimum storage size for a Solo60 is 650 gallons, for a Solo 40 - 600 gallons and for a solo 30 - 400 gallons?

These are a LOT smaller than some of the other numbers I have seen recommended/thrown around.

In any case, for the first year I am sticking with 500 gallons of pressurized.

Don't forget that they also sell tanks, which (the ones they sell) are expensive at any size, and rise substantially in cost as they rise in size- while at the same time they point out that gasifiers really perform best with a tank. So, in other words, while I don't think they are falsifying anything, their version of "optimum" may be influenced not only by overall system performance if you were looking at "best gallonage" without reference to price, but also by what they think the average customer can realistically swing financially, and/ or what will sell systems.

As an illustration of the many trade offs that can go into "optimum," the Honda Element I own is currently very "optimum" for my post-divorce, stagnant-economy budget, but it's a pale shadow of the Dodge Cummins 3/4 ton diesel pickup that I used to drive and that could always carry any and every heavy object I ever thought of wanting to drag home for a project.

 

[MrEd]

For me the only drawback of the "bigger is better" is the physical size of either 2 500 gallons or a single 1000 tank. My only point in reading the fine print was that maybe the 500 won't be so undersized after all for a Solo 60; my concern was that I was ridiculously under sizing storage; my only goal this year is that I can build just one fire a day and have the storage carry me to the next day's firing.

In any case, its what I have to work with this year and we shall see.

 

[DenaliChuck]

Your one fire a day requirement will drive the size of your tank. How many BTU's does your house consume over a 24 hour average day?

The Tarm will make 198,000 btu/hr which will supply the house for 5-6 hours and load the tank at the same time. The tank has to be sized large enough to store the btu's needed to heat the house for the other 18 hours PLUS the btu's lost by having heat stored for 18 hrs in a tank (not an issue if the tank is in your heated space). Calculate this and you'll know if your tank is large enough.

My relatively new, air tight, well insulated, 2,400 sf house needs the Tarm Solo 60 and 1,000 gallons of storage to make it through the average Alaska day (at least according to my calculations). We'll see if it holds true!

 

[MrEd]

In my situation, during the day we heat the main living space (kitchen, dining, tv room) with a woodstove which keeps it toasty, but does nothing for the bedrooms at the end of the house and upstairs. My plan is build a fire around 4-5PM to start pre-heating the bedrooms, charging the DHW for showers, and hopefully bank enough heat to get us thru to morning when we get the living space woodstove roaring again. I think it will work, but I am keeping my eyse open for bigger storage solutions I can put to use.

 

[Willman]

You could always add another 500 gal. tank to your set up. A few posters have those set ups.
Will

 

[pybyr]

For me the only drawback of the "bigger is better" is the physical size of either 2 500 gallons or a single 1000 tank. My only point in reading the fine print was that maybe the 500 won't be so undersized after all for a Solo 60; my concern was that I was ridiculously under sizing storage; my only goal this year is that I can build just one fire a day and have the storage carry me to the next day's firing.

In any case, its what I have to work with this year and we shall see.

presurized storage will let you go closer to or above atmospheric-pressure boiling point in your upper temperature limits, which will get you more BTUs-stored per gallon of storage, which is much to the good, and 500 gallons does not seem "ridiculously undersized" in your climate and if your house is well insulated and air sealed.

 

[pybyr]

In my situation, during the day we heat the main living space (kitchen, dining, tv room) with a woodstove which keeps it toasty, but does nothing for the bedrooms at the end of the house and upstairs. My plan is build a fire around 4-5PM to start pre-heating the bedrooms, charging the DHW for showers, and hopefully bank enough heat to get us thru to morning when we get the living space woodstove roaring again. I think it will work, but I am keeping my eyse open for bigger storage solutions I can put to use.

and if you have ideas underway as to how to juggle those priorities and loads to keep your gasifier running full-bore whenever it is full of wood, while charging storage as much as possible, and while also distributing heat appropriately (from gasifier and/ or storage, depending on each of their ambient BTU contents and source vs. sink modes) among priorities of DHW and heat zones, without a lot of software involved, I want as many gory details as possible, and as soon as possible

you are definitely describing the "ideal" that I am aiming for, but have so far I've only been grokking the BTUs and flows and piping diagrams- not control algorithms- of.

 

[MrEd]

In a nutshell this is what I am hoping for and building towards:

House is about 3000sf, moderately insulated at best with 40 year old windows.

Woodstove (Hearthstone heritage) manages to keep the primary area of the house toasty all day - the area that we are most likely to be in - about 72 degrees or more even on bitter cold days. Family of 6 home all day (I work from home, 4 kids are homeschooled, wife teaches )

Around 4PM I plan on building a fire in the Tarm, and my hope is that the house with its 5 zones of cast-iron baseboards, plus 500 Gallon of storage will allow the Solo to run full bore for 5-6Hours.

All zones in the house have programmable thermostats that will keep the bedrooms about 58 during the day, jump to 74 degrees at 5PM(while tarm is running), setback to 58 around 10PM, raises to 65 at 6:30AM, and drop back to 58 by 8:30AM.

During that 5-6 hour time period the tarm is firing all the bedrooms will be calling for heat and will likely be starting at about 58-60 degrees. The Superstor will also be calling for heat and a soon-to-be-built firewood pre-heater/ will also be left to run full-bore(more below). So, without having done all the detailed BTU calcs, I am think I will be able to run the Tarm full bore for the entire burn.

During the period when the Tarm is running, showers will be taken, clothes will be washed and dishwasher will be run so the superstor will continue to demand heat for several hours.

Tarm slowly burns out and hopefully that after all bedroom zones are satisfied, the DHW demand stops and Superstor and the 500G storage all end the day with full tanks of very hot water.

1 or 2 Morning showers will be run will run off the superstor and only need minimal heat from storage, storage will be available all day to top off the superstor and to satisfy the lower heat demands of the bedrooms during the day. If I find that I am getting close to my next firing time and there is still plenty of hot water in the tank, I will change all the bedroom zones to stay warmer all day to use up available heat. I think there is plenty of flexibiliy in my heat demands to use up BTU's or conserve BTU's if my "mental plan" doesn't match my actual results.

Firewood pre-heater:
I am also in the process of building a very simple firewood dryer/pre-heater that is a simple insulated box, hold about 20cubic feet of wood (about 2 days worth) sitting on a rack with a 9000BTU kickspace mounted under the pile of wood and a ventilation vent on the top. The kickspace heater will run off a simple timer that I will flip on just after building the Tarm fire each night. It will hold enough wood for 2 days, so each load will get 2 days worth of super drying before being used.

 

[Nofossil]

Sounds well thought out.

I use Carrier Debonair 33cs071 thermostats. They're not programmable for time-of-day, but they're remotely controllable. A contact closure switches them from 'occupied' to 'unoccupied', each of which can be independently set to a different temperature. My 'unoccupied' temperature is pretty low, and the thermostats are automatically switched to unoccupied if the wood boiler and storage are both cold (heating source is oil). This generally happens only if we're away for a few days.

These are also two stage thermostats - they have two sets of contacts. The first set provides contact closure when the house temp drops to the setpoint minus deadband (also programmable). The second contact closure happens If the temperature drops another 2 degrees. I use the primary contacts when I'm heating from the wood boiler, and the secondary contacts when I'm heating from storage.

Maybe overkill, but I don't have to touch thermostats. I don't do time-of-day setback because we have a well insulated house with very little baseboard. The house temperature drops very slowly, and comes back up even more slowly.