Minimize wood use with storage?

[goosegunner]

Just trying to get a feel for the best way to run my storage with my Econoburn.

The last couple days it has been low to mid 20's for a high and just below 20 for a night time low.

I have been charging my storage in the evening and ending about 10 pm to about 189 top and 185 bottom.

The next day about 4 pm it is reading 158 top and 140 bottom. I have forced air heat and the air is plenty warm down to 135 with my set up.

The actual boiler temp drops to about 100 to 110 degrees.

So I start the process again. I have not weighed my wood yet but it takes about a shopping cart. I do it gradually with 2 or three small loads.


So what do you find is the best Run it up to a high temp once a day?

or

Is it better to use smaller loads twice a day and not let the boiler and refractory cool down as much?

Any feelings on best way to minimize wood useage?

Does it make a difference?

gg

 

[taxidermist]

Right now I am running mine just like you when i am home. On my days I am have to work I build a fire at 04:30am load it 1 time before I leave @ 05:30. Then the wife loads it again around 07:30. She returns home around 18:00 and builds another fire gets a bed of coals going then loads 1 more time. The next day when I get home from work I build a fire around noon. This is in the dead of winter when we have been below 30* for weeks.

I charge to 180* top to bottom and use down till 120* I too have forced air and a flat plate for DHW


Rob

 

[flyingcow]

Learn your unit and heat load. You are doing just that. What I do might not work, but I think we're in the same thought process. I will do 1 fire whenever I think i need to. Drive my storage up to max temp for that time of year, might be once a day(cold azz winter) or once every 5 days(summer DHW). Shoulder season? Once every 2 days. Every season, means a different tank temp I am achieving. And it will vary when i think i will be home next. Sounds confusing, but run your unit and learn.

 

[Frozen Canuck]

Only concern I would have Goose is the possibility of condensation if the boiler drops to 100-110 °F on a regular basis. AFA the eff goes a large load burned flat out should be more eff than a few small ones. Less total energy wasted warming the boiler up.

 

[goosegunner]

Only concern I would have Goose is the possibility of condensation if the boiler drops to 100-110 °F on a regular basis. AFA the eff goes a large load burned flat out should be more eff than a few small ones. Less total energy wasted warming the boiler up.

The boiler temp is one issue I have thought about. in the morning the temp is still 140+. If I build a fire to put back some btus that I used during the night it would keep the system warm.

When the boiler is cold it seems to perform best if I do the charge with a small load first and then top off the coals when everything is nice and hot. I might add a few pieces a third time to finish the charge. It is running flat out the whole time just not with a full load of wood.

gg

 

[Frozen Canuck]

Yep, see that your working at it Goose, not that easy a nut to crack. More than a few threads lately about warm weather troubles. Who would have thought that a winter this warm (so far) would be a problem.

Still all in all a good problem to have. Better than thread after thread about folks not being able to stay warm as we head into our 6th week of -40. ;-)

Hope you find that just right size/time of load Goose. Won't be hoping for -40 to make it easier for you though....crap that would be a steady -60 here.

 

[goosegunner]

Learn your unit and heat load. You are doing just that. What I do might not work, but I think we're in the same thought process. I will do 1 fire whenever I think i need to. Drive my storage up to max temp for that time of year, might be once a day(cold azz winter) or once every 5 days(summer DHW). Shoulder season? Once every 2 days. Every season, means a different tank temp I am achieving. And it will vary when i think i will be home next. Sounds confusing, but run your unit and learn.

What temps do you consider shoulder season? Meaning what temps typically let you go two days.

gg

 

[jebatty]

If shoulder season is not having to burn every day, then every day is shoulder season for me. Even with last winter cold down to -36F, I burned no more often than about 6 hours once every other day. As to warm/hot storage and cool/cold boiler, some turn on the boiler circulator, open the bypass to the boiler protection device, and warm the boiler up before or during the early stage of firing. I don't bother.

 

[chuck172]

How about keeping an eye on the storage tank bottom. Use the boiler protection minimum as the temperature point to charge the system. Most cases 140*.
Do this twice a day for 500 gallon storage, once for 1000 gallons of storage.

 

[barkeatr]

people talk about the condensation from cooler temperatures coming into boilers. Where does that happen on the outside of the water jacket or inside, or both? I understand that this is addign thermal stress on welds also..but Im curious on the condensation part.

barkeater

 

[mwk1000]

How about keeping an eye on the storage tank bottom. Use the boiler protection minimum as the temperature point to charge the system. Most cases 140*.

That is how mine is set up, I check for a few things before deciding to turn on the tank curclator pump, Here is an example of midday when the fire is out and the tank is heating the house (SF = source feed at HX, BR= Boiler return at rear of boiler) When all the checks pass the pump is engaged.

Get Temps... DONE^M
SF < TANK - relay OFF 130.10/141.10^M
BR low - relay OFF 133.70/140.00^M
Delta low - relay OFF 0.90/2.00^M
log:SourceFeed:F:130.10^M
log:SourceReturn:F:131.00:-0.90^M
log:LoadFeed:F:119.50^M
log:LoadReturn:F:120.40:0.90^M
log:BoilerFeed:F:135.50^M
log:BoilerReturn:F:133.70^M
log:TankSen1:F:139.10^M
log:TankSen2:F:149.90^M
log:TankSen3:F:151.70^M

 

[goosegunner]

How about keeping an eye on the storage tank bottom. Use the boiler protection minimum as the temperature point to charge the system. Most cases 140*.
Do this twice a day for 500 gallon storage, once for 1000 gallons of storage.

That is right about where I am at with recharging. Yesterday I was 158 top 140 bottom.

As far as stress on the system wouldn't the use of low temp emitters to maximize use of storage down to 100 degrees result in a shortened life span?

gg

 

[ihookem]

Goosegunner, I don't have storage so I can't say about high and low storage temps. I have believed that a boiler that stays hot for 4 months will last longer than a boiler that gets one or two super hot burns, then the fire goes out. Two days later when the boiler steel is 0* ya start another super hot wide open fire in it. I've always suspected this is as stressful on a boiler weld as starting an engine in the cold and running it hard before it's warmed up. I think storage will save a bit of wood if you can run the boiler almost constantly. I notice how much more wood it takes just to get the 1,400 lbs of boiler good and hot just to let it cool back down wasting a lot of btu's. Once boiler is hot the water heats faster. Just some observations and thoughts.

 

[goosegunner]

Goosegunner, I don't have storage so I can't say about high and low storage temps. I have believed that a boiler that stays hot for 4 months will last longer than a boiler that gets one or two super hot burns, then the fire goes out. Two days later when the boiler steel is 0* ya start another super hot wide open fire in it. I've always suspected this is as stressful on a boiler weld as starting an engine in the cold and running it hard before it's warmed up. I think storage will save a bit of wood if you can run the boiler almost constantly. I notice how much more wood it takes just to get the 1,400 lbs of boiler good and hot just to let it cool back down wasting a lot of btu's. Once boiler is hot the water heats faster. Just some observations and thoughts.

ihookem, Did you ever locate any tanks?

One thing I can tell is that I am enjoying my boiler a lot more so far this year. No need to get up and make sure the boiler is loaded, no need to rush home to throw wood in. I will have to run my gas furnace periodically because with storage it doesnt get a chance to run as the back-up.

gg

 

[ihookem]

I can get 2 120 gal. compression tanks that are new. They are 800 bucks for the both. I think I am going to go with a propane tank and put it in my garage. This will mean more piping but it will only be 30 ' from the forced air furnace so it won't be much piping. I wanted the tanks in the basement but the garage corner will be ok. Your buddy in Shawano that sold you a tank had one 500 gal. tank and would not fit in my garage corner. 2 250 gal tanks will though. I'm still looking but not too serious. Thanks. Still wonder though if starting a cold boiler and running it hot is hard on the welds.

 

[goosegunner]

I can get 2 120 gal. compression tanks that are new. They are 800 bucks for the both. I think I am going to go with a propane tank and put it in my garage. This will mean more piping but it will only be 30 ' from the forced air furnace so it won't be much piping. I wanted the tanks in the basement but the garage corner will be ok. Your buddy in Shawano that sold you a tank had one 500 gal. tank and would not fit in my garage corner. 2 250 gal tanks will though. I'm still looking but not too serious. Thanks. Still wonder though if starting a cold boiler and running it hot is hard on the welds.

Never too late to put a small addition on your garage. 6'X6' on a gable end wall would give you room for a vertical 500 pipe as a hydraulic separator.

gg

 

[huffdawg]

people talk about the condensation from cooler temperatures coming into boilers. Where does that happen on the outside of the water jacket or inside, or both? I understand that this is addign thermal stress on welds also..but Im curious on the condensation part.

barkeater

Its kind of like a toilet tank without insulation on the inside . cold water on the inside, warmer air on the outside causes the outside of the tank to condensate .Or like a ice cold beer on a hot day the outside will condensate. In the boiler it would be cooler air hitting the outside of the waterjacket (exhaust side ) causing it to condensate. IE. when the fires out.

I'm sure someone else will probably come up with a better explanation for you.

Huff

 

[jebatty]

I notice how much more wood it takes just to get the 1,400 lbs of boiler good and hot just to let it cool back down wasting a lot of btu’s. Once boiler is hot the water heats faster.

Wasted btu's can be eliminated by locating the boiler and storage in a space to be heated. I know this isn't possible in many cases, but anyone who has put their gasifier in a shed quickly notices how much heat is generated. I think you are correct that the boiler heats faster with hotter water, which results from a hotter burn and generation of more wood gas. For my burn yesterday, at start of burn boiler was 78F, top of storage was 128F and bottom of storage was 118F. At the same time as I started the fire I opened by bypass to the Termovar and switched the boiler/storage circulator on. In just a few minutes the boiler was up to 120F, storage dropped to 124F. It would have taken much longer for the burn to bring the boiler up to that temperature, and boiler temperature then climbed rapidly with this hot water priming.

 

[hobbyheater]

[quote author="goosegunner" date="1323402108"]Just trying to get a feel for the best way to run my storage with my Econoburn


What I have done is keep track of the wood that is burnt in each situation. I have a blackboard in the boiler room for this. My findings is this; the longer and hotter the burn, the greater the efficiency of the boiler. I do enjoy cutting wood, but find satisfaction in getting the most heat possible out of that wood!
I'm using 30 year old gasification technology that has a large refractory component .

Allan

 

[HeatFarmer]

At the same time as I started the fire I opened by bypass to the Termovar and switched the boiler/storage circulator on. In just a few minutes the boiler was up to 120F, storage dropped to 124F. It would have taken much longer for the burn to bring the boiler up to that temperature, and boiler temperature then climbed rapidly with this hot water priming.

Jebatty, how do your have your system plumbed to achieve this? I'm using low temp emitters and plan to run my system similarly....load up the heat storage to max and then let it drop to around 120 before firing again. Isn't it a bad thing to allow the cooler return water to enter the boiler? Isn't that the point of the Termovar? I was planning on having my Danfoss set at 140º...but then my boiler will be indoors on a heated slab, so it shouldn't be stone cold when I start either......

 

[maple1]

I think it's bad to let cooler water return, when there is a fire going and condensation potential in the flue gases. If the fire is out, that potential is gone.

 

[jebatty]

Heatfarmer: Jebatty, how do your have your system plumbed to achieve this? ... Isn’t it a bad thing to allow the cooler return water to enter the boiler? Isn’t that the point of the Termovar?

Here is a simplified schematic of my plumbing. Balancing valve before the Termovar; bypass loop with a ball valve to preheat the boiler from storage to the storage temperature before firing. The boiler circulator normally would come "on" at 160F, but I also have a manual switch to turn it "on." After the boiler is preheated to the storage temperature, the bypass valve is closed and the circulator is switched "off.". This is not allowing cooler return water. The boiler may have cooled to as low as room temperature, while storage still may be quite warm (100-130F). Preheating the boiler to storage temperature gives the boiler a start-up boost. Then the Termovar and normal circulator control takes over.

Maple1: I think it’s bad to let cooler water return, when there is a fire going and condensation potential in the flue gases.

There is a lesser condensation issue resulting from the boiler preheating than there is when cold starting the boiler because the boiler is now warmer than it is on a cold start and the boiler heats up faster.

 

[DaveBP]

There is a lesser condensation issue resulting from the boiler preheating than there is when cold starting the boiler because the boiler is now warmer than it is on a cold start and the boiler heats up faster.

Jim, so the advantage of doing this is that the boiler itself gets up to optimal operating temperature faster. But you're not saying that the whole BTUs-into-the-storage-tank cycle is any shorter. Or is it?. Can you tell from your data logging?

And so to go on from this idea... Instead of injecting that colder water (that was in the boiler) into the top of the tank, what if you had a second circulator aiming in reverse of the main circulator and used that to take that cold water out of the boiler and put it back into the bottom of the tank. This would use the hottest water from the top of the tank to heat the boiler faster and would also not mix the cold water from the boiler with the hottest water in the top of the tank.

This would cost more for a circulator than your system as is with a simple switch, of course.

By the time I get a little farther along into this cup of coffee this added complexity might seem a little silly but do you feel "pre-heating" the boiler is worth the effort if it is easy?

 

[jebatty]

Dave - yes, the boiler itself gets up to optimal operating temperature faster. And also then the time to get BTUs into storage is faster, but at a cost. Preheating the boiler from storage drops storage temperature. I wasn't data logging when I last did this, but based on my sensor 1/3 down from the top of tank storage temperature dropped by 2F to preheat the boiler, so that would have to be made up on the charge cycle.

Since I burn no more often than once every other day, the boiler itself is somewhat above room temperature (I have a little ghost flow) on the start of a burn. It takes quite a long time to bring the boiler up from 80F+/- to the 160F temp when the circulator is turned on, and lots of BTUs also then are going up the chimney. If the boiler is at 120-130F when fired, as opposed to 80F, that 50F preheating really shortens this time and my guesstimate is that there is a net gain in overall efficiency due to fewer BTUs going up the chimney on start-up.

Drawing hot from top of storage and return of cold boiler water to bottom would be better. In my situation this is not important as my entire storage is used for radiant floor with the injection mixing valve set at 100F.

I do feel that "pre-heating" the boiler is worth the effort and it is easy. Easier yet would be a zone bypass valve and a differential controller that automatically would start the circulator, open the bypass valve, and then shutdown when the boiler was pre-heated to near storage temperature.