Burning with no storage

[chuck172]

My sophomore year with the Tarm. I've always used my 500 gallons of pressurized storage. For the heck of it I'm burning without it today. I'ts not real cold out, 30*.
It runs good! I'm surprised. I have the boiler aquastat set to it's lowest temp. The boiler shuts down at about 180*. Idling most of the time but kicks in nice when there's a call for heat.
I know it's "taboo" to idle, but I'm experimenting. This may sound strange, I know idling a gasification boiler is inefficient, but I think I'm burning a heck of allot of less wood. Normally I'd burn all out for about 4 hrs. then work off the storage, 500 gallons of storage doesn't last very long with fintube radiation. When I get down to about 160*, it's time to light up again.

 

[DaveBP]

Seems kind of paradoxical, doesn't it? But if you're not able to use water below 160F, supplying water below that temperature even at 100% burn efficiency isn't going to be very helpful.

Is your pressurized storage connected directly and not through some heat exchanger? If there are no other HXs in there about all you can do with storage is to wind the boiler up and keep it going until the entire tank is up to 180F or so. You could tweak your overheat limit aquastat as high as it will go (I see photos of Hansson's and other storage thermometers over there above 200F) and get more usable BTUs stored but you have to work to get it in there. It makes very good stratification imperative when you need the higher temps to be useful.

It would take some careful experiments with accurate measurements to prove it but you might be right. Running your boiler without storage during some times of year may be more efficient in terms of actual pounds of wood burned per day to stay comfortable.

 

[chuck172]

Thanks for making that observation Dave. This is something I have to look into more deeply. It's just against my nature to let my boiler idle like this. I normally never her idle.

 

[mtnmizer]

Currrent temp here is 10 with -30 in the near forecast, winter has arrived
with a shout.

I'm running without storage at this time, however I have the components on
hand, just need to form the copper coils and put it all together. It will
definitely make the should season easier to manage.

I will say that so far I'm very satisified with the performance of the EB150
without any storage. With baseboard I can keep things warm even with water
down to 130 at night. My propane boiler is set to kick on at 125 which keeps the
house nice to wake up to. I get around a 6 hr burn at night with the thermostats
at 65.

The upper chamber has some shiny black stuff on the door and upper surfaces but the lower
chamber is light cream colored and the stack had only soot and no
creosote. Wood use is around a 3 armloads a day which for this big of a house
is really efficient. I really could do just fine without any storage IMO. MM

 

[chuck172]

mtnmizer, You must have really oversized the amount of baseboard to have it keep the house warm @ 130*. Fintube is normally figured at 180*.
I believe that low temp emitters (panel radiaters, radiant heat etc) are the real key to efficiency with these boilers utilizing storage.

 

[willworkforwood]

Chuck172; is your boiler in the basement, or close enough to make loading reasonably convenient? The reason I'm asking is that we run without storage, and have become very good at knowing what size fire to burn in order to meet the current and upcoming heating load, and at the same time avoiding idling most of the time (overnight idling does occur of course). But, the boiler is in the basement, along with over a month or so of wood, and my wife is at home while I'm at work. So it's no problem at all for us to load smaller amounts more frequently (and the boiler likes to hear the thank you each time I load ;-) ). So, if it's isn't a big pain for you to load, have you tried more frequent smaller fires to cut down on the idling? This isn't a knock on storage - I would have it myself, to handle the shoulder season better, but it's not in the budget right now. But if you're experimenting, it might be another thing for you to try.

 

[chuck172]

The boiler is in the basement. I am using partial loads, Just a few pc's at a time.

 

[willworkforwood]

So, If I'm understanding correctly, you're loading just a few splits but still idling? If your experiments are just from the past week or so, then maybe the warm temps are skewing the results. Your're warmer in NJ than I am here, and I've been having a tough time figuring things out this week - I actually had the boiler shut down almost 2 days in a row because it was just too warm outside. But, in "normal" cold weather, I can usually load enough to run for 1-3 hours without the boiler temp hitting the idle point (not 100% but fairly close). Have you tried just a few splits in colder weather?

 

[mtnmizer]

mtnmizer, You must have really oversized the amount of baseboard to have it keep the house warm @ 130*. Fintube is normally figured at 180*.
I believe that low temp emitters (panel radiaters, radiant heat etc) are the real key to efficiency with these boilers utilizing storage.

Can't say if it's oversized or not, the 130 temp is on the low side at the end of an overnite burn. I doubt
I could heat the house full time at that temp.


I seldom ever see much over 165 if all the zones are running. The boiler is in the basement and I have radiant slab there
so thats a big plus. I charge the slab in the evening after the house comes to temp and the boiler goes to
idle, then refill for the nite.

At night I open the overheat zone manually and it contributes some too during the idle periods In any regards these
boilers are terrific. When the storage is functioning I expect to do less fiddling.. MM

 

[deerefanatic]

I've been idling my Eko60 while trying to get my storage up and going... It's doing ok, but using plenty of wood. Part of that I think is due to user habit (I don't have time to be messing with it constantly, so when it gets filled, it gets filled to the top) and my house and shop are both being heated off it, as is about 100 gallons/day of hot water in the milk barn........

Right now, my shop is drawing hot water about 18 out of every 24hrs, and it's only getting into the teens at night...... I think I'm going to have to bump the water temp up some more pretty soon..........

 

[chuck172]

How about this for a plan. I do have 500 gallons of pressurized storage. I heat the storage to its maximum. 193* or so. Then I load the boiler and let the boiler take care of the heating load. This way the boiler aquastat would have to cool down to 160*, then and only then would my limited storage kick in.
I figure I would get a fair amount of boiler idling, but it might be the best of both worlds.

 

[lawandorder]

What is the best way to heat just storage versus answering the demand for heat?? Do you just isolate the storage tanks so the circulation is between tanks and Tarm?? What happens if there is a call for heat?

 

[flyingcow]

I'll chime in on my system. I followed tarms layout/controls. The system does it automaticlly. Just fired up boiler, house calls for heat, priority is the house(have heat coming thru baseboards in 30ish minutes). Whatever heat isn't used for house will be dumped into storage. fire goes out then the flow is reversed on the hx and this feeds the house.

 

[chuck172]

Right now my storage is 192* and my boiler water temp is 190*. It is idling. I have about 1/2 load of wood in the boiler. My heating loads will tap the boiler heat first, then when the boiler temp drops below 160*, it will shift to the storage tank. This setup should give me plenty of heat time. Hopefully it should take me easily through the night .
Temps will drop to the low 20's high teens. My superstor is superheated to 150*

 

[chuck172]

I'm on to something here. It's 4:30 AM, (I'm going hunting), I loaded the boiler about 1/2 full yesterday evening about 7:30 PM. My storage was 192*, boiler temp 190*. Now 9 hours latter my storage is 195* (thanks tekmar 156) and boiler temp is 172 with live coals remaining.
O.K I admit my thermostats were turned down to 67*, and no domestic hot water was used but ordinarily I would have depleted my storage to an unusable temp of about 160*.
Temp dropped to 21*outside, my total home heatloss is 61,000 btu/hr.
I'll take loading the firebox up at night and waking up to coals anytime. Problem being, the boiler idles. How much- too much for my tastes.
I'm wondering how harmful this idling condition is?

 

[Birdman]

Thank you for your thoughts on this thread. I will hopefully be getting storage within the year and ahve been curious on how it works... and how it will help me. Chuck... your info is very helpful. When your Tarm is done providing heat to your house.. and it switches over to the 195 storage... how long did that storage last you? I know the storage lasts when the outside temps are different... so I am looking for your data in this current weather you are in now. I have a Tarm solo 40 as well. I keep my house hotter 70-72 all the time.. I think this helps me stop idling? I fill it up and can not be home all day.... so my thought is... keep the house warm all day.. and prevent idling if tarm is outputting more?

 

[chuck172]

500 gallons of storage @190* really doesn't last long at all. Once the temp. falls below 170*, it really isn't very effective and then really cools fast. I'm sure someone can do the math and let you know how long 500 gallons will last at a given heat loss rate.

 

[Birdman]

Chuck. What is your sq ft you are heating? HOw long does your 500 gallons of storage last you right now when it is all heated to max? 2 hours? 4 hours? 6 hours? 8 hours? I am just looking for an estimate... to decide on how much storage i would want in future. In your circumstance... would you do storage again if you had the choice? Would you go bigger?... or not at all?

 

[chuck172]

I'm heating aprox. 1800 sq. feet.
My storage will usually take me through the night with therms. low, and no h/w usage.
Other than that storage goes fast, again once I get down below 160, storage starts to cool real fast and it seems like the pump never shuts off.
I'm waiting for someone to chime in with the math. That will let you know exactly how many btu's are available with 500 gallons.
I should have doubled the tank capacity in the first place. I figured the first 500 gallon tank was step 1 of 2, I'd like to stack another. My better half say's "no way, she's sick of looking at that "mon-strau-city" in the basement.
She's a tough nut to crack.

 

[Birdman]

So I am assuming when you say your 500 gallons of storage takes you through the night... that you heat your storage to capacity and it gives you 8 hours of heat... under the current weather conditions? Is my estimate correct that if you had 250 gallons of storage that the time would be in half as well?

I am thinking of getting storage. However... I do love the idea that more storage gives you longer times to heat with. But... would smaller storage suffice ? Explain to me what would happen to your routine if you had 250 gallons of storage? And.. with smaller storage could you still prevent idling?

 

[stee6043]

500 gallons of storage with usable temps between 180 and 160 will provide 83,300 useable btu's per charge. Most folks see average heat loads between 20k-30k per hour. Assume 20k per hour loss and 500 gallons will provide roughly 4 hours of heat.

I personally see my useful temp range being a little wider. I can heat "relatively okay" with 140 degree water in my water-air heat exchanger. Anything below 140 and my furnance fan runs way too long and like Chuck the water seems to be cooling and mixing too much for the amount of heat your getting. You can surely tell when you're reaching the point of diminishing returns on storage temps.

My setup stacks up like this: 1000 gallons of storage with useable temps between 180 and 140. This gives me roughly 333,000 useable btu's per tank charge. My average heat load is right around 20k per hour (3,200 square feet, newer home, pretty tight). So for a charge of 333,000 I can get right around 16 hours of useable heat from my tanks. My average daily burn is in the 7 hour ballpark. During the burn I heat storage and the house. Soooo....I have a system that effectively heats my house 24 hours a day on 5-7 hours of burning depending on the whether. With anything less than 1000 gallons this would not be possible in my case.

 

[chuck172]

There you go Birdman, I knew someone here would come through with the math.
"500 gallons of storage with usable temps between 180 and 160 will provide 83,300 useable btu's per charge. Most folks see average heat loads between 20k-30k per hour. Assume 20k per hour loss and 500 gallons will provide roughly 4 hours of heat."
thanks stee6043

 

[Gooserider]

From what I've seen Birdman, 500g is on the low side of usable storage capacity, I would say that most of the folks here are running closer to 1,000g, which seems to work pretty well in most installs...

The math is pretty easy, you get ONE BTU of storage for each pound of water per degree of usable ΔT - or difference in temperature between charge and discharged.... Thus there are two ways to increase your BTU capacity, either increase the tank size, or increase the useful ΔT....

If I was in Chuck's shoes, and wasn't allowed to add a second tank, I'd be trying to talk my way into increasing the amount of baseboard, or better yet, putting in panel rads or infloor radiant so as to get a wider useful temp range out of the tank...

Gooserider

 

[chuck172]

That's what I feel is the key to this whole wood-gasification-boiler game. Low temp heat emitters.
Panel radiators, in-floor radiant heat.

 

[chuck172]

"500 gallons of storage with usable temps between 180 and 160 will provide 83,300 useable btu's per charge. Most folks see average heat loads between 20k-30k per hour. Assume 20k per hour loss and 500 gallons will provide roughly 4 hours of heat.:

So realistically speaking, I'm actually loading 5cu. ft. of wood into the tarm, heating storage for aprox. 4hrs. to get my 500 gallons of hot water to 190*, then only pulling 4 hrs. of heat from the storage.
That's 8hrs. heat/5 cu. ft. of wood. Not too good!