Storage tank size

[stoney28]

I'm sure this has been answered in other threads, but I haven't found them in the hour I've been searching these boards.

What size storage tank goes well with the EKO 40?

I tried to use the info in the manual to come up with a minimum size, but it mentions the EKO 25 has 31 KW (Kilowatts?, how does that work?) in that example. They don't give the amount that the EKO 40 has, and I can't seem to find it anywhere.

 

[Green Mtn Boy]

I don't have an EKO but I assume that it would be based off the BTU rating. I'm guessing an EKO 40 is comparable to a Tarm Solo 40 or about 140,000 BTU/HR. If memory serves me correctly, I think I remember Tarm tell me the suggested minimum tank sized were as follows:
Solo 30 - 600 gal.
Solo 40 - 750 gal.
Solo 60 - 1000 gal.

Again these are minimums. I have a Solo 30 and I'm planning to use 750 gal of storage when I get around. It depends a lot on what you can find for tanks. I know guys that have 500 gal for a Solo 30 and 1000 gal for a 140,000 btu/hr boiler like yours and they both work fine.

 

[Nofossil]

The size of storage depends on the heat load. Ideally, you want at least enough storage so that it can carry the house for whatever portion of a 24 hour day the boiler isn't burning.

For instance, I need about 360,000 BTU for the next 24 hours. That will require me to run my boiler about 6 hours. When my fire is done, I'll need enough heat in storage to last the remaining 18 hours - about 240,000 BTU. I get about a 40 degree usable temperature range from my storage, and I have 880 gallons. That works out to about 290,000 BTU of usable heat if the storage is fully charged - more than the 240,000 that I'll need.

Interestingly, a larger boiler requires more storage, since it doesn't burn as long to create the necessary heat. That leaves more hours out of the day that you have to heat from storage.

On a really cold day I'll need as much as 720,000 BTU. That means that I need to burn for 12 hours and I need to store 360,000 BTU. That's more than my tank can hold, so I have a problem on really cold days.

 

[Reggie Dunlap]

Don't know what EKO recommends but I have 750 gallons for my Tarm 40 and I wish I had more. Install as much as you can afford and have room for and you'll be happy. More storage equals less wood used and you can be a lot more flexible on when you need to run the boiler.

 

[chuck172]

"More storage equals less wood used and you can be a lot more flexible on when you need to run the boiler."

The less wood used part is debatable. It takes less wood to heat less storage. It is true you will need to burn more frequently with less storage, but you'll burn for shorter intervals.

 

[sweetheat]

tarm 40 with 806 gallons of storage, storage tank went from 105 degrees this morning to 180 degrees, my limit at 3:00 P.M two small fires. I'm sure you could use a larger tank with the EKO, or you could go with a pressureized system and capture even more BTU's, sweetheat

 

[stee6043]

One thing I'd like to add for those getting into storage - give it time. It takes an ungodly amount of time and wood to bring 1000 gallons of cold water up to 180/160. I was shocked by how long it took me when I fired up my system last week. I basically loaded my EKO 40 three times per day for four days in a row to bring my storage up from 57 degrees. And she was running full tilt in gassification pretty much the whole time. I'd say it only idled for a total of 30 minutes over four days. I was getting 4-5 hour burns per load. I'm just now reaching 170 on the top of the upper tank and 155 on the bottom of the lower tank. For the first day I was absolutely unable to heat the house while charging the tanks. There just wasn't enough hot water to go around when the Danfoss is seeing 60 degree water from the system.

Of course my first three days were spent running with the owners manual air settings. Today I changed primary and secondary settings to get a bluer flame and seem to be getting more heat, and more flue temp. So that may have helped had I done it earlier....but it's a learning experience at any rate.

 

[stoney28]

I have 500 gallons of storage right now, and I'm not happy with it. I filled up my furnace this afternoon and burned less than half of the firebox before it brought the storage up to 180 so it smoldered longer than I like. I'm thinking of pulling out the 500 gallon this summer and replacing with a 1000 gallon tank.

 

[in hot water]

Also, the larger the delta T or temperature range you can utilize, the more energy stored. To this end size the heat emitters to use the lowest possible temperature. Radiant floors, ceiling, or walls are ideal with low temperature.

I use 500 gallons with my EKO. Charge it to 180- 185 range, and I can pull it down to around 100 for radiant concrete slab distribution. So I have a large delta T to leverage.

If you system requires a minium of 150- 160, you have less useable storage.

A BTU is a BTU, they have no way of knowing if they are being wrangleds for heating or parking

The very best place to store energy is in the un-burned wood. Once you combust it, changing chemical energy to thermal energy, it starts slipping away from you, and eventually mother nature will get it all back.

I'm of the opinion storage can in fact be over-done driving overall efficiency down at the cost of non burn cycles.

Plan the system, emitters and storage size and insulation to you ideal scene.

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