Tarm Solo 40 versus Solo 60

[MrEd]

I asked this question buried in another thread, but I started a separate thread too.

I am going to order a tarm very soon. I will have 1000 gallons of pressurized storage, and now having made the decision to invest the money, thinking of all the extra things I can heat "for free". Hot tub and the pool come to mind, in addition to the 3000sf house. Also maybe add a small greenhouse next spring - seems once the heat is free, you come up with uses for it.

So the question is, if the proper size tank for a Solo 60 is 1000 gallons, and if I have that, is there any reason not to get the 60 versus the 40? Not having used a gasifier, my assumption is that basically that since all the heat is going into the tank, the 60 will get the tank(s) upto speed quicker than the 40. I could see that if you had no tank you would want to be very careful about sizing the boiler, but with adequate storage, does it really matter?

The $600 difference is cost is minimal given the cost of the whole system, but what am I not taking into consideration?

 

[Eric Johnson]

Others may have a different opinion, but I'd go for the 60. The tank negates most, if not all, of the reasons for not oversizing.

 

[EricV]

One thing to take into consideration is the possibility of needing to use larger (more expensive) pipe and fittings to move that heat from the boiler to the tank, house, greenhouse, etc.

I used 1" on my 40 (they call for 1.25" but the cost was too much more.) and it's borderline but still works good. It goes into sleep mode very little.


On the 60 it is another 33% more energy to move.

Just a thought.

Eric's right (of course) if your heating the tank then you heating it faster with the 60.

 

[Nofossil]

The 60 is no problem as long as you're planning on burning it in the preferred 'gasifier' pattern: short hot burns with extended cold periods between. If you want to keep it going for extended periods, that will be harder and less efficient with the larger boiler.

Think of it this way: If the boiler is just a tad larger than the heat demand, it can run for a very long time before the storage is 'full'. You would then let it shut down until the storage is depleted, then repeat. A larger boiler will spend less time getting the storage up to temp, and therefore require more start/stop cycles.

 

[MrEd]

Can't you control the burn by just loading less wood?

 

[Nofossil]

Can't you control the burn by just loading less wood?

No - that just makes it burn for a shorter time. In my case (with an EKO 25) I need to burn for about 12 hours a day when it's really cold. I have enough storage to last about 12 hours when it's really cold. Works out to on long fire each day. If I had a larger boiler, I'd only have to burn for 6 hours. 12 hours later, I'd have to build another fire

It's probably easy to get obsessive about this. An idling gasifier is no worse than a conventional boiler. It's just that they're MUCH more efficient than a conventional boiler when they're running in gasification mode, which means near full output.

There are some European models that can modulate over a wider range than models available here, but it seems to require oxygen sensors to get the proper air/fuel ratio over a wider range of output. The EKO and the Tarm seem to be much more efficient at high output.