Storage will . . . and Storage will not . . .

TCaldwell said:

Jim, i am not familiar with a tarm's internal hx/ transfer to water setup, when you mention flue temps/ to rated output, isn't the flue temp dependant in part on the to the water temp the hx tubes are seeing, for example given the same process gas temp entering the hx tubes, with cooler water the tubes wil shed more heat , resulting in a lower flue temp and a higher combustion effiency calc. If the entering water temp is higher the hx tubes shed less heat and show higher flue temp and a lower combustion effiency, even though the boiler is delivering the same process gas temp ,ie same fire size to the hx tubes the flue temp will differ, creating a different rated output. I am not sure flue temp alone is a indicator of rated output. My experience is with a garn, i can watch with the same secondary burn temp[process gastemp] that with starting water temp of 140 , my flue will be 265, high effiency calc, as the boiler water temp rises to 200, my flue temp will top off at 300. Basically for me a lower flue temp = higher effiency for the same output. i know you have some thoughts!

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I would like to answer "yes, no, maybe," and probably I generalized too much and this likely is way more complicated than what I see from observation. And since I didn't write down data showing flue temp, supply temp, return temp, and gpm flow at variations of each of these, I'm going to reply at this time from a rough memory.

At low water supply temp, say 100F, I can quite easily obtain approximate rated output of 140,000 btuh with a flue temp of 465F and supply temp of 175F; flow = 3.5 gpm +/-. To accomplish rated output at return of 160F, supply temp of 188F, I will need flue temp of about 515F; flow = 9+ gpm. Incidentally, my typical burn usually will hover right around 465-480F and may start to creep up as system return water temp rises above 160F. I think we pretty much agree.

Clearly, your Garn flue temps are lower and the Tarm are higher. Lots of potential reasons for this, including different secondary combustion/gasification temperatures; different heat extraction design; one being more and the other being less efficient in converting wood to heat energy, and probably many more. How this relates to overall efficiency is an interesting question. It would be fun to have a gasification boiler and Garn with the same output rating (need to be based on the same method of calculation), same amount of water storage and insulation, same lbs. and types of wood, same water starting temperature, and do a side-by-side burn to see how many btu's each extracts to its storage. That would seem to give an overall efficiency result. Maybe this has been done? At the same time data could be collected on flue temp, etc.

What's funny to me is that with my wood stove in the house I just load it with wood, burn, get heat, and pay attention to keep the stack at 300-400F when I need heat. No measurement, no desire to measure, only a desire to stay warm. What is it with one of these boilers that drives some of us to learn more and more, experiment, pretend like we know something, and tell others about our experiences? Beats me.

This discussion has been very useful for me. I had intended to install storage sometime before next Fall, but now think I will wait for another season. As a first season user my learning curve has been pretty steep. I can't think of any other appliance that I've owned that challenges me like keeping those water and thermostat temps up. So for me it's been a challenge... keep the house warm, debug the system, and learn how to use this thing. Messing with this boiler has a lot of similarities to getting a race car sorted out. I think that is why many of us find it so interesting because peak performance doesn't come by flipping a switch.

I've just added two AZEL digital temperature gages to my system to get a handle on my boiler efficiencies. I have sensor pair where boiler water leaves and enters the PEX at the boiler shed and on the in/out at the HX. A stack temp thermocouple will be here in a few days.

For this first season unless the outside temps get up above 30-40F my boiler rarely hits idle. Where I'm going with this is whether its my poorly seasoned wood or that our BioMass 60 is undersized for our inefficient home I don't know yet. But I'm very glad as a DIY'er I didn't try to debug storage in addition to getting the kinks out of boiler, unseasoned wood, adding sensors, etc. Had I paid a bunch for a professional installational I'd feel very different, but like most here I'm bumbling thru it with ya'll help. From this discussion I've learned that I won't burn a bunch more wood next season when I'll have properly seasoned wood and other improvements. Because at the moment since our boiler is rarely idling I don't know if I have any excess energy to dump into storage until outside temps get above freezing. Good discussion thanks.

Jim, If my feeble memory serves correctly, you are involved with a install of a downdrafter next to a garn, maybe a willing test bed,how is that going?

Jim I think you would need to know the peak combustion temperature or effective combustion temperature too, the flue temperature is one of the temperatures in the heat transfer equation but the combustion temperature is the other. It is a delta T calculation.

My guess is that every appliances will have a different pair of values.


TennMan: I wouldn't back away from installing storage. There are lots of benefits; installing storage is not that hard to do, price is low and it is sure convenient. If that is what you are looking for, then go for it!

Tennman said:

This discussion has been very useful for me. I had intended to install storage sometime before next Fall, but now think I will wait for another season. As a first season user my learning curve has been pretty steep. I can't think of any other appliance that I've owned that challenges me like keeping those water and thermostat temps up. So for me it's been a challenge... keep the house warm, debug the system, and learn how to use this thing. Messing with this boiler has a lot of similarities to getting a race car sorted out. I think that is why many of us find it so interesting because peak performance doesn't come by flipping a switch.

I've just added two AZEL digital temperature gages to my system to get a handle on my boiler efficiencies. I have sensor pair where boiler water leaves and enters the PEX at the boiler shed and on the in/out at the HX. A stack temp thermocouple will be here in a few days.

For this first season unless the outside temps get up above 30-40F my boiler rarely hits idle. Where I'm going with this is whether its my poorly seasoned wood or that our BioMass 60 is undersized for our inefficient home I don't know yet. But I'm very glad as a DIY'er I didn't try to debug storage in addition to getting the kinks out of boiler, unseasoned wood, adding sensors, etc. Had I paid a bunch for a professional installational I'd feel very different, but like most here I'm bumbling thru it with ya'll help. From this discussion I've learned that I won't burn a bunch more wood next season when I'll have properly seasoned wood and other improvements. Because at the moment since our boiler is rarely idling I don't know if I have any excess energy to dump into storage until outside temps get above freezing. Good discussion thanks.

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If you're boiler is essentially running full out anytime the temp outside is below 40F, it is severely undersized, you have extremely wet wood, your losing heat underground in your runs, or your house is very poorly sealed, or all of the above ! My boiler will idle for hours when the temp here gets up to around 20F outside. At 40F it would smolder most of the day. Something sounds awfully wrong with your situation. I wouldn't even consider putting in storage until you can figure out why your doing so much burning. Even with wet wood it should eventually get burning good enough to cycle off and on a few times during the day.

I'm not trying to pick on you, but something is not right with your house/boiler system. IMO, there is no way that boiler should be running flat out when its 30F outside.

Pat

involved with a install of a downdrafter next to a garn, maybe a willing test bed,how is that going?

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A feeble memory is better than no memory, which sometime afflicts me. Yes, I am involved. Last week I called the director and offered to do some temp data logging. The first measurements likely will be on both sides of the hx for the Garn to pressurized system. I would like to verify that the hx is performing in accordance with the specifications for the system and that the Garn, as being fired, is performing within its capability. Next some measurement on the Wood Gun. There was a hope that the Garn could function as storage for the Wood Gun. The hx was plumbed counter-flow Garn to system, and without a plumbing change, the flow will be parallel on Wood Gun to Garn. I haven't found anyplace that provides specs on parallel flow, and the mfr/supplier of the hx has not been helpful. Some temp data logging will provide a great picture of whether and how well this will work.

mikeyny said:

I use to use a lot more wood than I do now. It took me several seasons to learn how to run my boiler with out storage more efficiently. Loading times vrs boiler temp outdoor temp and wood species takes a while to get the hang of. i have no real data other than I know my house is warmer and I use less wood now because I am smarter than I used to be about how to load on a regular basis. i would add storage if I had the space,time and money, but I don't. I need the space for the beer storage fridge. There is another newbie thread going on here right now about what to buy and I am cheap. I suggested a good old used tarm was a good start, but if he has the dough, go for the caddilac.

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the beer storage fridge is essential in a shop

Patch and Jim, I don't think our boiler is undersized, but all the rest you mentioned is probably true. Been bringing in wood from the hills as fast as we can, so this season the wood is dead but not seasoned. When I do run thru a batch of wood pretty dry there is a big difference. I know our 150+ year old house is very inefficient, and in about a month which will be pretty much the end of our heating season, I'm going to dig up my PEX and redo. So no, not undersized, but all the rest you said applies for this season. BUT all in all we're happy. Propane use is negligable except to knock the morning chill off. But my highest priority for next season is lots of wood stacked asap. Our 110kbtu propane can keep the downstairs warm, so I'm pretty confident a 210kbtu boiler can get there. I may still do the storage, but for me lots of dry wood is more important for next season. I work in the city where the crazy professor shot 6 people last Friday so we're pretty far south. As I type this I'm looking out at beautiful white snow. Very rare for us. So to top it all off my first season with our wood boiler has set cold records in the south. But I'm still enjoying this whole process.

get a cheap moisture meter from ebay Tenman. You'd be surprised how wet dead wood can be.

My supply lines are 50 ft long so 100 ft round trip. I dug them in 5' deep and put 2"x12"x8' pcs of foam board over the top. They are also insulated in a 6" tube. I get very little heat loss to the ground. I don't think you could insulate them to much.
Doug

Doug, Before you decide to dig up your pex, purchase a inexpensive ir gun and check your temps at both ends of supply side, also scrounge up a load of known dry wood and see how the boiler responds.

Tennen, I can tell your house is an air sieve. Inulate the attic and you will notice a big difference. another thing I do with my house is shovel snow up against my house. My uncle used to take hay bales and line them up tight against the outside of the house. This makes a huge difference. I keeps air from getting in and lots of air gets in through the bottom of the siding. My house is brick and it still helps keep the basement a little warmer. We talked about this a month ago or so. So far I have burned 2 1/2 cords of wood from poplar to oak mixed, but it's dry.

Be careful on thoese IR temp reader. I have a good quality one and readings are all over the place. Just my 2 cents

Deere10 said:

Be careful on thoese IR temp reader. I have a good quality one and readings are all over the place. Just my 2 cents

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Technique matters a lot with an IR gun, especially on small round targets like pipes... If you don't shoot them the same way every time the readings will vary unpredictably...

IMHO, you are far better off putting some kind of thermometers on the line and getting really consistent readings - the ideal would be some kind of data logging setup w/ sensors all over the place.

If you must do the IR gun, you will get better readings from iron or copper pipe than you will from PEX. Paint the spot on the pipe black, or put a piece of black electrical tape on it. Shoot straight onto the spot at as close to a right angle as possible, and while keeping the gun close to the target, and using a consistent distance. (If you are to far away, you will be reading both the background and the pipe...) The idea is that you need to get rid of as many sources of error as possible, and make what's left consistent, so that any changes in the reading are definitely due to temp changes, not technique changes.

Gooserider