Anyone else feel wood consumption increased with storage?

[woodsmaster]

Yes inverted 120 gallon lp tank. Wirsbo hepex sight glass with thill ice fishing float for level.

gg

Any significant heat loss from this tank?

I doubt it the tank pressure/ temp gauge is usually not that different from room temp. Room temps are similar to what it was last year with out storage and the new pressure tank.

I don't think I have ever seen a insulated expansion tank?

gg

I dont think it would make much of any difference in wood consumption but im going to insulate my expansion tank to help keep
the boiler room temp down. Mine does get pretty warm to the touch when the boiler is running.

 

[Duetech]

Nofossil has tank sensors placed at different heights all the way down the storage tank so he can tell just how much sotred heat he has so do you know how much of your tank is getting charged and at what temp? Is there a gentle flow going into and out of your tank (water mixing from excessive turbulence skewing your stratification?) what temp is your water getting to before you recharge? How are you extracting the heat (radiant, panel rads, base board or air water hx?) [sounds like air water hx off the cuff guess]. I ran my EKO for four years with no storage and ran it all year long though at a reduced rate in summer for dhw and never went over 7 cord. Some think when a gasifier is idling it's a smoke dragon but mine showed little to no smoke depending what stage my wood was at (wood, coke or coals) and sometimes the auto purge provided all the gasificaton needed for hours and a refill was more often less than 75% capacity because of unburned fuel. It's capacity is 6.5 cu ft when stuffed. Sorry I don't have a btu calc to help you find actual used heat from your system compared to your heat loss calculation but it sounds to me like you have a big heat sink somewhere in your system that went un-noticed before the storage came in to play.

 

[goosegunner]

I am waiting for a new pump to arrive, the first 26-99 I installed was doa. My calculations on paper indicate I am flowing 11 gpm with my 15-58. A 26-99 should flow 18gpm on medium and 22+ gpm on high. I can take my tank to 190 top and 186 bottom but it does seem to eat more wood last 10 degrees.

My tank charges pretty even with low return temps right to the end.

My garage lines going to furnace in basement are not covered very well. It is 51 degrees in my garage right now with a outside temp of 30 degrees. Those lines run on demand this year so maybe I am bringing water back that is colder than it should be do to poor insulation on the lines in garage. It has been this way for 2 years and it was fine but it might be hurting my storage temps.



Gg

 

[ihookem]

Goosegunner, I read your post on real cheap lp tanks you posted a few months ago. Can you give me that number?? Thanks in advance.

 

[DoubleClutch]

I hate to say it but I might have to weigh a few of my wood loads before I burn. It is just a gut feeling, but to me it seems as though my wood consumption with my Econoburn 200 and 1000 gallons of storage has actually increased after adding storage.

Some say this seems to defy the laws of physics, but not to me.

Heating a larger mass of water to a given temperature, and then maintaining it at a given temperature (due to losses, which you will always have unless you have a perfect insulator, which is unknown in this Universe), will always require more energy than doing the same with a smaller mass of water.

Raising the temperature of one pound of water by 1°F requires one BTU. It's not just a nice convention – it's the law.

You might get less cycling with a larger heat sink – but you're always going to require more energy to heat it to temp and maintain it at temp.

 

[stee6043]

Some say this seems to defy the laws of physics, but not to me.

Heating a larger mass of water to a given temperature, and then maintaining it at a given temperature (due to losses, which you will always have unless you have a perfect insulator, which is unknown in this Universe), will always require more energy than doing the same with a smaller mass of water.

Raising the temperature of one pound of water by 1°F requires one BTU. It's not just a nice convention – it's the law.

You might get less cycling with a larger heat sink – but you're always going to require more energy to heat it to temp and maintain it at temp.

I'd first like to nominate the above two posts for the "best revival of a very, very dead post" for 2013. 13 months is not bad. Since this is January 1st I think this is a well deserved award!

Second, just about everything you said above would only be true if the "large mass of water" is outside the heating envelope of the building you are trying to heat. I believe all EU installations and a vast majority of US installations will have the tanks inside the home. As such, once a tank begins to lose heat it's losing it to the building and is ultimately contributing to the reduction of the net heat load. This is not lost energy.

It is not the intent of thermal storage to "maintain" tank temperatures. The goal is to put btu's in and almost immediately begin taking them out again. Nobody is trying to get their tanks up to 180 and keep them there all winter long. That would 100% negate any benefits thermal storage offers a user and I don't think you'd ever find a wood burner operating in this fashion.

I'm sure Goosegunner will come along and see this post he started in 2011. It'll be interesting to hear his take a year later...

 

[goosegunner]

Ok here is the update.

First thing to say is storage adds an incredible amount of convienience. Whether it be winter or summer pool heating the boiler can run full bore and any excess heat not used by the load goes to the tank. Because my system is used for pool heating my storage is remote from my house. Makes no sense to have warm pipes and tank in house if I am running the air conditioning.


Now on to wood consumption;


I have found below 30 degrees with my forced air coil I prefer to keep warmer water at the top of my tank. To do that I do 2 smaller fires a day which take 5-10 minutes to start.

I now do weighed wood burns just for an example when the weather has been

25 high
0 low


Morning 50lbs of wood
Evening 70lbs of wood

To put that into perspective I dried a piece of cherry in my boiler room for 6 months to 15% moisture.

18" long
13" diameter
Weight 46lbs

So in reality my wood consumption is not very much to heat my home and partially heat garage as my pipes are not the best in garage but on the above temps it will be about 50 in garage.

gg

 

[goosegunner]

To any that have not installed storage, it is worth every penny as far as I am concerned. The important thing for me to add is when I do the 2 fires a day there is a very large window on when I do them.

Whenever it is convenient could be 6 or more hours either direction. I just do one in the morning and sometime in the evening.

gg

 

[JP11]

Exactly.. It's all about convenience. If it's sunny out.. and I'm not using a lot.. I might run the storage all the way down to 135 top, 125 bottom.

If it's cold.. and I'm going to bed in a few hours even if storage is 170.. I might stuff the boiler full. Letting it bounce off idle thru 3 or 4 hours at night when I'm asleep.. and i heat the house till noon the next day. Or.. I reload at 150 the next morning.

Great convenience. With oil for a backup (i've used less than 20 gallons since oct 1) and burning JUNK hemlock at the moment.. I'm ecstatic with my purchase.

 

[goosegunner]

Exactly.. It's all about convenience. If it's sunny out.. and I'm not using a lot.. I might run the storage all the way down to 135 top, 125 bottom.

If it's cold.. and I'm going to bed in a few hours even if storage is 170.. I might stuff the boiler full. Letting it bounce off idle thru 3 or 4 hours at night when I'm asleep.. and i heat the house till noon the next day. Or.. I reload at 150 the next morning.

Great convenience. With oil for a backup (i've used less than 20 gallons since oct 1) and burning JUNK hemlock at the moment.. I'm ecstatic with my purchase.

That is one thing I have not tried yet, running a load and letting it idle. I have considered it but I don't want to get creosote in the boiler if I don't have to. When it gets cold I have taken storage to 190/186 top/bottom.

I guess I would need to turn my set point down a little to have it idle on and off.

gg

 

[goosegunner]

Another thing about storage and emitters. Even though I can get heat a pretty low temps with my forced air coil. It does feel the same if water is 140 vs 170.

I think that is where the radiant would be really nice, a lot more even warm heat with low temps, Am I correct with that asumption?

gg

 

[JP11]

The few times I have been working in the basement when I force it to idle from over fueling...

I don't really get much creosote. I'm not idling a long time... as I only over fuel it when the house is actively using quite a bit of heat. I bet I don't go 15 to 30 minutes without the fans spinning up. I'm sure my flue temps aren't great.. but I bet they stay in the 200 to 250 range.

with the min fan speed set at 25% now.. I seem to be able to hover in the 190 to 196 range on storage and it goes quite a while. No real science there... but I clean the tubes every 3 weeks or so.. and I'm pretty happy with how it works. Am I getting PEAK efficiency.. probably not. I am getting max convenience though.

JP

 

[Floydian]

I think that is where the radiant would be really nice, a lot more even warm heat with low temps, Am I correct with that asumption?

MRT-mean radiant temperature and comfort go hand in hand. Here is a good explanation of the physics: (broken link removed to http://www.healthyheating.com/Definitions/Mean%20Radiant.htm#.UOMaVXeQP8k)

Noah

 

[Fred61]

I can heat when my unpressurized storage is down to 100 to 110 but my 200 feet of DHW coil doesn't make my water hot enough for a comfortable shower.

 

[DoubleClutch]

Second, just about everything you said above would only be true if the "large mass of water" is outside the heating envelope of the building you are trying to heat. ... As such, once a tank begins to lose heat it's losing it to the building and is ultimately contributing to the reduction of the net heat load. This is not lost energy

It's not lost energy, true, but it IS going to require more energy to heat. The OP seemed surprised that adding capacity (increasing the mass of his heat sink) added to his fuel consumption. Others commented that this seemed to defy the laws of physics. It doesn't defy the laws of physics – it obeys them.

It takes more heat to increase the ocean temperature by 1°F than it takes to increase the temperature of a cup of coffee by 1°F.

Even if adding storage allows you to store the warm water at a lower temperature, since you'll have more of it (larger mass at a lower Δt), you're still going to have losses, most particularly in the efficiency of your heat exchanger in the firebox.

 

[stee6043]

It's not lost energy, true, but it IS going to require more energy to heat. The OP seemed surprised that adding capacity (increasing the mass of his heat sink) added to his fuel consumption. Others commented that this seemed to defy the laws of physics. It doesn't defy the laws of physics – it obeys them.

It takes more heat to increase the ocean temperature by 1°F than it takes to increase the temperature of a cup of coffee by 1°F.

Even if adding storage allows you to store the warm water at a lower temperature, since you'll have more of it (larger mass at a lower Δt), you're still going to have losses, most particularly in the efficiency of your heat exchanger in the firebox.

Clearly we are not talking about the same thing. If you get every BTU you put into storage back out of storage it is not phyiscally possible that having storage increases wood consumption. In fact, many folks will notice slight decreases in wood consumption as a result of adding storage because it will enable a boiler to run idle-free. That was my original point back in 2011.

You may see increased per-burn energy output requirements to fully charge a thermal storage system but you should see an equal and opposite effect on the frequency of your required burns, all things being equal.

 

[skfire]

Another thing about storage and emitters. Even though I can get heat a pretty low temps with my forced air coil. It does feel the same if water is 140 vs 170.

I think that is where the radiant would be really nice, a lot more even warm heat with low temps, Am I correct with that asumption?

gg

Absolutely..I run my storage down to 104f.
All my radiant zones are mixed down and even at the lowest of 104f tank temp or as low as 96f in Primary loop, I have observed return water as low as 75f. Fine for short term or maintaining floor heat for short periods of time(not when it's 8f outside, like this morning).
Key is consistancy in suplly to radiant...night setbacks can be killers, even though I do set my zones back only 1F at night and during mid day..

Scott