Garn WHS3200 & Wood Gun E500 – Another Night Out [Part 4]

[jebatty]

See Part 1 for general information; Part 1 and Part 2 for specific information on the Garn; and also Part 3 for additional pictures.

Wood Gun E500 - Update

Plumbing Problem Data Fix
The plumbing problem I identified earlier with regard to the WG was an incorrect installation of the mixing valve to provide return water protection to the WG. It was installed backwards with the effect, based on the sensors, of mixing down the WG supply to 160F based on the return line location of the mixing valve control sensor. The net effect was to mix-down WG supply to the system to about 165F+/-, as well as more than likely creating some return/supply turbulence in the area around the valve which affected my temperature sensors from the burn a week ago, resulting in the anomaly I mentioned. To obtain accurate readings of WG supply and return temperature, I moved my return sensor to a point about two feet above the return fitting on the WG, which also was more than10 feet from the mixing valve. I moved the supply sensor to a point between the WG supply fitting and the circulator, which is installed on the supply line with the mixing valve on the opposite side of the circulator. At these locations any turbulence in the pipes caused by the mixing valve which would impact temperature sensor readings should be nonexistent.

Successful Burn and Mother Nature Cooperated
The weather forecast was cold, with forecasted night temps to get down to -15F. As noted below, Mother Nature held more than true. As with last weeks’ Garn test burn, Deep Portage was in low occupancy status, so occupancy/system demand conditions were as close as possible to identical of the prior week

The Garn had been allowed to burn out and its firebox to cool down before the start of the WG test burn period. I left the Garn and Garn HX circulators “on,†however, so that the Garn 3200 gallon tank could operate to provide some buffering storage capacity for the WG supply, in the event the WG supply exceeded system demand, which otherwise would cause the WG to go into idle cycles. This strategy proved to be of benefit during the test period, as Garn tank temperature moved up and down within a 5F range during the WG burn periods, so the Garn tank definitely was buffering excess WG output to the system. This buffering capacity is not available when the Garn is being fired simultaneous with the WG, and the WG has idled when both boilers have been fired. Dedicated pressurized storage for the WG would be of benefit to Deep Portage to allow the WG to operate most efficiently independently of the Garn.

The results:

A. Burn Rate. As for the prior week, BTUh input during the WG test burn is estimated at 600,500 (100 lbs/hour, 6,050 BTU/lb, 20% MC, 400F flue temp), same as for the Garn. I loaded the WG at the rate of 100 lbs on the hour, with one exception, that being one load of 125 lbs to see if the WG could burn at a rate higher than 100 lbs/hr. It cannot, as at the end of that hour there still was a good quantity of unburned wood in the firebox. With 100 lb loads, at the end of each hour the fire would be down to low burn (some mostly burned logs plus coals).

B. WG Temperature. The WG analog temperature gauge on the front started at 174F at 3:00 pm (outside temp of 4F), rose to 183F by 6:00 pm (outside temp of -2F), and then stayed mostly between 178-181F, up and down, until 5:00 am (outside temp of -18F) Saturday morning when the test burn ended. I ended at this time because system temperatures had fallen to a point not sufficient to maintain interior temperatures at the desired level. The “desired†minimum system supply temperature is 140F.

The WG temperature gauge reads about 5F higher than the sensor measuring WG supply, just as with the Garn. During the entire burn WG temperature gauge supply temperature ranged between 172-183F, up and down; WG sensor supply temperature ranged between 167-176F, up and down, and WG return temperature stayed at a virtual constant Correction: 151F.I attribute a significant part of the variation in supply temperature to coals blocking the slots to the gasification ceramics and impeding gasification burn in the WG. Several times I had to rake the coals away from the slots to make sure that they were open, and after doing this supply temperature would rise. This procedure is recommended in the WG manual.

C. BTU Input. Beginning at 3:00 pm on February 25 and ending with at 5:00 am on February 26, the WG burned 1,433 lbs of wood, which at 6,050 BTU/lb amounts to 8,669,650 BTU input.

D. BTU Output. I had Dallas 1-wire DS18b20 sensors located as mentioned above. This data showing delta-T WG supply/return along with calculated flow rate shows BTU output. The chart which follows shows WG measured supply and return temperatures. From the data underlying this chart, I averaged delta-T, which was 23.74F degrees. Flow rate is calculated at 50 gpm. BTUh = 23.74 x 500 x 50 = 593,500. Total hours = 14. For the 14 hour period, BTU output was 8,309,000.

E. Efficiency. Based on BTU input of 8,669,650 and BTU output of 8,309,000, efficiency can be calculated by BTU Output / BTU Input, which is 95.8%, vs 86% for the Garn.

F. I also was able to log WG flue temperature, as it has an accessible steel flue fitting on the bottom of one side which received hot flue gases immediately as they exited the WG. I drilled a hole and inserted a probe K-type sensor into the center of the flue. Flue temperature were consistent between 420-480F, high burn and low burn included. Following is a chart showing WG flue gas temperature over the burn test period from 5:00 pm to 5:00 am.

 

[jebatty]

Comparison [Part 5a]

The Deep Portage side-by-side installation of the Garn WHS3200 and the Wood Gun E500 allowed a unique opportunity to test the capacity of each boiler under near-identical operating conditions. This test was not for the direct purpose of determining which boiler better met the needs of Deep Portage, although the test information will better allow Deep Portage to use each boiler separately, and both together, to improve the ability of the boilers to meet its heating needs.

Ease of Use and Maintenance: Both boilers are very easy to use, but the Garn is easier to use than the Wood Gun.
A. Garn
It is very easy and fast to start a fire in the Garn. A little bit of kindling, a few small splits, start the kindling, turn on the blower, and the fire takes right off. The Garn firebox lading door is about at waste height and is large, circular in shape. This makes it very easy for nearly everyone to toss in splits, even if they are quite large and heavy. The only use disadvantage of the Garn that I noticed was the build-up of coals and raking the coals to provide an even bed in the refractory when the Garn is used to provide long term, continuous output, which necessitates daily, or perhaps more often, shutting down of the Garn by letting the coals burn out and removing accumulated ash. The Garn manual that Deep Portage received states that the Garn is intended for “intermittent†use, which I take to mean firing to bring the Garn up to a desired temperature, letting the fire die out, drawing hot water from the integral storage tank, removing ash as needed, and the firing again on the “intermittent†basis. Even though the Garn is intended for intermittent use, Garn sold the WHS3200 to Deep Portage as suited to the needs of Deep Portage, which were continuous, long term burning with need for hot water (140F+) and large demand. The Garn does not excel in this operating environment. I have no experience with any required other maintenance with the Garn, although I am aware that other maintenance is required.

B. Wood Gun
I did not start a fire in the WG but I have no reason to believe that fire starting is difficult, although I cannot imagine it being easier than the Garn. The WG physical stance is higher than the Garn, and the firebox loading door is rectangular with a metal flap at the top to prevent smoke rollout when the door is opened. This higher stance and shape of the loading door makes it more difficult than the Garn to toss in large, heavy splits. I am 5'9" and 155 lbs, and loading was by no means difficult, just not as easy as with the Garn. The WG is well-suited to continuous, long term operation at full burn capacity. Coals do have to be raked to prevent them from blocking the gasification slots, and while this is not hard, it needs to be done periodically during a long term burn. This is also stated in the WG manual. I also have no experience with any required other maintenance with the WG, although I am aware that other maintenance is required.

Heating Capacity - BTUh Output
A. Garn.
The Garn is rated at 925,000 BTUh “burn rate.†On other posts users have stated their belief that this means output. My test burn did not test the maximum output of the Garn, which I assume would need to be done on an “intermittent†basis. I tested long term, sustained output. As Part 2 shows, total output over the 19 hour test burn period resulted in average, sustained output of 472,500 BTUh, or 51% of the “burn rate.â€

B. Wood Gun
The WG is rated at 500,000 BTUh output. During my long term, sustained output test burn, total output over the 14 hour test burn period resulted in average, sustained output of 593,500 BTUh, or 119% of rated output. Although I do not recall where I read from users that they believe their WG boilers (not necessarily the E500) had an output greater than rated, my test burn verified that in fact for the E500 output exceeds the rating by nearly 20%. If long term, sustained output is the heating need, then the WG likely is a better choice than the Garn.

The higher BTUh output of the WG also is demonstrated in that, in nearly identical operating conditions, except outside temperature, the Garn maxed out its ability to maintain Deep Portage system temperature at an outside temperature of +10 to +11F. The WG maxed out its ability to maintain system temperature at an outside temperature of -8 to -10F. Obviously, for both boilers, a change in system demand would affect this outcome. These test burns were at Deep Portage “low occupancy.â€

Hot Water Output
Garn measured output temperature averaged around 148F, and WG measured output temperature averaged around 179F. This relates strongly both to the large heating demand at Deep Portage and some level of return water protection for the WG but not the Garn. In high demand applications, and if hotter water is needed, the WG is better suited than the Garn to providing hotter water. Garn also has advised Deep Portage that the Garn does not meet its best application if water hotter than 140F is required.

Flue Gas Temperature
The Garn ranged between somewhat under 400F at the end of each hour and the time of refueling and somewhat greater than 600F shortly after loading and very high burn, with the bulk of the burn in the 450-550F range. This is an observation based on the Garn analog thermometer, as I was not able to place a probe to measure temperature. I don’t know where Garn measures this temperature. The WG ranged between 420-480F, low to high burn, and was very consistent, as the chart shows. Past reading has indicated that a 100F drop in flue temperature corresponds to about a 2% increase in efficiency. The WG appears to be more efficient in capturing BTU’s to water than is the Garn, which also is borne out by the overall efficiency calculation.

 

[jebatty]

[Part 5b]

Efficiency
The Garn calculated efficiency is 86% and the WG calculated efficiency is 95.8%%. The Garn manual states 84% efficiency of BTU transfer to water, but WG makes no representation in this regard. I assume that the 84% Garn efficiency number is based on maximum output during an intermittent burn.

My two efficiency ratings need to be taken with some perspective, as they both are based on certain assumptions.

The first assumption is wood at 20% MC. Regardless of actual MC, both boilers were fueled with wood seasoned under the same conditions, similar mix of oak and other species, and similar split sizes, so if actual MC was different, the change in efficiency should affect both boilers the same.

The second assumption is flow or gallons per minute (gpm), which was calculated at 75 gpm for the Garn and 50 gpm for the WG. I measured the pipe and fittings and calculated pump head for each (including the HX for the Garn and the mixing valve for the WG). I also applied the pump head against the pump curves for the respective circulators, and found that GPM was at the approximate calculated rates. I have no way to calculate actual gpm. This means for the Garn that each 1 gpm of actual vs calculated, BTUh changes by 37,500 and efficiency changes by 1.3%, and for the WG the change is 25,000 and efficiency changes by 2%. Depending on the direction of change, efficiency goes down or up.

The third assumption is the accuracy of measured temperature. The DS18b20 sensors should be accurate to 0.5%, but any sensor I placed could have a better or worse thermal contact with the pipe, so error may be different. I did the best I could to place all sensors in the same manner.

A Final Word
I am not a scientist, and I cannot attest to pure scientific rigor in making these reports. All I can state is that I did the best I could to apply my knowledge and experience to measuring the performance of two boilers, installed side-by-side, serving the same facility, and under near identical operating conditions. My comments relate only to these models of Garn and WG. I do not know whether a test of other models would produce similar results.

I hope this report is helpful as others may choose which boiler to purchase.

 

[Duetech]

That's quite an endeavor. Thanks for the input. Frankly I hope I never have to have a unit that burns 100# per hour unless I have someone much younger do the work.

 

[Como]

I was wondering if you had any thoughts as to why there would be such a difference in efficiency.

You mentioned that the Wood Gun was not so well insulated and kept the Boiler room warmer. The exhaust temperatures do not seem to be that much different, does the Wood Gun has a smaller blower so it is not exhausting so much heat?

 

[jebatty]

Some of this for sure goes beyond any expertise I have. As to efficiency alone, the lower flue temp for the WG is part of it. I looked up my notes on efficiency related to flue temp, and the actual note is 1% increase in efficiency for each 40F drop in flue temp. So maybe 3% or so of the efficiency gain is related to lower flue temp.

Both the Garn and Wood Gun were burning the same weight of wood, so I have to "guess" that the Wood Gun hot gases are passing through the HX tubes more slowly to transfer more BTU's, and/or that the WG has more HX surface area, or ? Part might be due to the design of the WG for 500,000 BTU output, lower volume of draft induced air moving through the system, vs the Garn which has the 925,000 BTU burn rate, high volume of air moving, and design to achieve rapid transfer of heat to a large volume of water under intermittent burning? I don't know the cfm ratings of the draft blower design on the two boilers.

It seems to me that 86% for a wood boiler is pretty darn good, and higher for the WG is even better. I have done efficiency calculations on my Tarm and the result was 86% in transfer to water storage, plus for many hours while the Tarm is burning the building in which the Tarm is located is fully heated by "waste" heat off the Tarm, piping, and flue.

The boiler room is hotter with the WG than the Garn mostly because, I believe, the entire Garn, except for the door area, is insulated, while the WG is not insulated and there are hot surfaces on the boiler itself.

 

[Como]

Had a look on both sites, they both seem to use 3/4hp electric motors,so you would have thought that they might have a similar ish flow?

The number for the Garn does not surprise me, the WG just seems too good to be true.

Would it be possible to work out how much energy was being exhausted and how much dissipated into the Boiler room?

The only other thing would be if the Wood Gun had a more complete combustion.

 

[jebatty]

I tend to think that both the Garn and WG are high, and more precise gpm would help to get a more accurate number. Assuming Garn is laboratory correct on 84%, I know my procedures are not that precise, and for me to get a higher % is surprising. The comfort I have in higher efficiency with the WG is that it held system temperatures with a 20F lower outside temperature than could the Garn while burning the same amount of wood, so I know it has to be more efficient. Also, there is very little ash with the WG, while a fair amount with the Garn.

As to combustion, I tend to regard the WG type boiler as more "true" gasification and maybe more efficient than the Garn process, but who am I to say? When I consider my Tarm, I can burn pine 6 hours or so and end up with about 1 cup of ashes, so I know the "true" gasification boilers are very efficient as measured by the amount of ash.

This test burn is the only experience I have had either with Garn or WG, so maybe I'm just speculating on anything beyond what the data showed.

 

[ewdudley]

Had a look on both sites, they both seem to use 3/4hp electric motors,so you would have thought that they might have a similar ish flow?

The number for the Garn does not surprise me, the WG just seems too good to be true.

Would it be possible to work out how much energy was being exhausted and how much dissipated into the Boiler room?

The only other thing would be if the Wood Gun had a more complete combustion.

Heat flux calorimetry is a tough racket, a couple hundred milli-kelvins inaccuracy here, a percent or two mass flow rate error there, and pretty soon you're off in the weeds. It's just plain difficult.

On the other hand, a couple of the storage heating tests that have been reported here have shown some pretty solid measurements. Just mix the tanks before the test, record three or four sensors at as many different levels, weigh and burn the wood with no loads drawing from storage, re-mix the tanks and record the after burn temperatures. The absolute temperature measurement errors cancel out and the only source of error is in the ability of the sensors to measure the difference between two temperatures, and averaging multiple sensors should tend to average that error away.

In the WoodGun / Garn test here it might have helped to compare the deltaT sensor pairs together in the same sensor well. Also some flue gas analysis might have provided some valuable basis for comparison of the two boilers and for corroborating other measurements.

--ewd

 

[Como]

It would be interesting to get comments from those who have the smaller breatheren.

I have read here the the WHS200 at 425,000btu is understated. Not sure is anybody has fired them continuously however.

 

[jebatty]

ewd: In the WoodGun / Garn test here it might have helped to compare the deltaT sensor pairs together in the same sensor well.

I agree this might help, but I don't know how it could be done. Each boiler has its own supply/return lines to the primary loop and the issue of flow still would be present as each boiler has its own circulator and they operate at different flow rates. If there are any plumbing patches to make this work, that would be quite expensive and likely involve shut-down of the system, neither of which is something Deep Portage would want to undertake.

ewd: ...some flue gas analysis might have provided some valuable basis for comparison of the two boilers and for corroborating other measurements.

If I had the equipment, I would have done it, even though I'm just a volunteer to Deep Portage. All of my time is contributed along with $$$ in equipment, parts, etc. My wife probably thinks I'm having an affair, or that I'm nuts, each time I tell her I'm spending another night at Deep Portage. Do you think she's right on the nuts part?

Como: Had a look on both sites, they both seem to use 3/4hp electric motors,so you would have thought that they might have a similar ish flow?

Could be true, but I wonder how the Garn then efficiently could support a 925,000 BTUh burn rate while the WG efficiently supports a 600,500 BTUh burn rate? It seems that the Garn would require more oxygen to sustain a higher burn rate.

 

[PassionForFire&Water]

What are the firebox volumes for both units, Garn and WG?
If the firebox volume of the WG is much smaller, I can imagine that the firebox temps would be higher and this could be an reason why the efficiency is higher.

 

[jebatty]

What are the firebox volumes for both units, Garn and WG?

From the websites for each, Garn 36 cu ft, WG 22 cu ft. These boilers are much different in burn technology and in how they transfer heat to water, and I doubt firebox size has much to do with comparative efficiency. Edit: In addition, I would assume that each has designed its firebox to maximize efficiency of the boiler.

 

[TCaldwell]

hi jim, I always enjoy reading about this test, regardless of the use of the outcome of the results you have a substantial time investment that i applaud. As a garn user since 06, what suprises me is the 600deg flue temp. even if the measurement was observed at the last pass thermometer and not the back of the appliance, basically garns share the same hx design and inducer motor but have different radial axial fans. i have only once without turbulator had a flue temp that high, and with a load of bioblocks, not cordwood. Not hearing of another 3200 user, i don't know what the norm is for flue temp or static cfm, but as you observed a lower than hoped for output, if these were observed in my 1900 model, i would conclude the flue tubes dirty. The gaskets if carefully removed can last through many cleanings. jim i wonder if the boiler was misfired early on, and poorly cleaned by unknowing well intentioned operators. I am not flawing your data, but either the 3200 has different burn charisterics than it's breathern or the tubes need a good cleaning and a observation at reburn.
tom

 

[jebatty]

tom: I am not flawing your data, but either the 3200 has different burn charisterics than it’s breathern or the tubes need a good cleaning and a observation at reburn.

I can't answer the specific question and I have no other experience with the 3200. Something of interest, though, is my finding of 86% efficiency vs Garn's manual statement of 84% efficiency. I tend to think my finding might be somewhat high, and how this relates to the flue temps, + or -, is a matter of interest. If Garn would provide some info, that could be helpful.

 

[heaterman]

This stuff is addicting isn't it? As to explaining the affair @ Deep Portage to the wife.........I can offer no sound advice for that.

A couple observations. I have never had the opportunity to play with a 3200 but knowing the integrity of the design,...I'll just say that 600* on the flue temp is a lot higher than the rest of the Garn's I have observed. Something is amiss there.

I concur with EW in that a flue gas test would really help to verify and establish baselines of performance. Your method is about as good as you can get by weighing the fuel load and measuring temperatures but there are just too many variables to make much of a solid conclusion. For example, if the EG was indeed cracking out 95% net efficiency, flue gas condensation must occur. Given it's absence, one would have to assume that 95% was not indeed being achieved. Condensing the exhaust gas from 100#'s of wood should produce about a half gallon of liquid. Also given the fact that flue gas condensation cannot occur at the stack temps observed, there must be some other variable at play that's not being picked up. I don't know what the answer is on that.

Reading between the lines regarding the overall system at Deep Portage, I think the number one thing they could do to help their situation would be to update their heating system to operate well with lower temp water. I don't know the age of the facility but I'm guessing that they have fan coils with rather meager output/* of water temp. The difference in performance of a 4 row coil vs a standard 2 row has to be seen to be believed. I am aware of another learning center in Minnesota that has 4 3200 Garns installed. For years they struggled to heat the place and went through mind boggling amounts of wood. The 4 units installed there could barely keep up. After changing the coils and addressing some severe transmission losses in their distribution piping, they no heat the place using only 2 of the 3200's and have cut their wood use in half. That facility is around 80,000 sq ft IIRC.
In the case of the facility you are helping out there......I have a hunch that if laid my wrenches on it, the system would be piped to use the WG as the base load unit and it would feed the storage of the Garn. The Garn would be fired up when outdoor temps demanded to augment the output of the WG. Not ideal but without knowing the system intimately that's probably the best judgment I can make from here. Best case from the boiler standpoint would be to somehow get rid of the hybrid scenario they have there and get two boilers with the same operating characteristics to work with. The situation they have there now is less than ideal because the WG and the Garn operate differently by design. As it stands right now they don't play well together. Having two Garns or two WG's rather than one of each would have made their life and the installation much simpler.

Getting back to the Garn flue temp............you should observe around 450-475 as a peak and it should level off at around 325* before tapering off at the end of the burn. Given that temps are elevated about 100 degrees or so above that and knowing the air volume moved through the 3200, an "in me head" calculation tells me that they are losing about 100,000 btu excess heat out of the exhaust. Someone there needs to roll up their shirtsleeves, get out the brushes and soot vac and have at it this summer.

gotta run.......

 

[muncybob]

Interesting on the efficiency stated. I recall in my 1st year with our WG I was having some condensation issues. An AHS tech person said that in part, due to the low stack temps(a result of high efficiency) I was having these issues. Those issues have since been resolved

I must say that after just about 2 heating seasons we have been pleasantly surprised in the amount of wood that has been burned to keep our house comfortable although I would have no idea what the efficiency % would be. Based on what we knew going into wood burning we expected to burn 5+ cords/yr...been lucky to be under 4/yr so far.

It was stated that ash build up wa minimal in the WG runs....you are referring to inside the firebox, right? We do get a fair amount of ash in the cyclone ash drawer.

 

[jebatty]

I think the biggest uncertain variable I have is gpm flow. A downward adjustment by a few gpm starts to make a noticeable change in performance/efficiency, and vice versa. I wish I had access to a flowmeter that could provide that info, as it would narrow the analysis of the data.

Although a "perfect" measurement under "perfect" conditions would be useful, I'm wondering whether that or whether a measurement after a period of use provides the best info to a user. With my Tarm, I will get different results depending on how clean the HX tubes might be, and a measurement just after brushing them may give an optimistic impression of performance, while a measurement after a couple of weeks of use may give a more realistic "real world" impression of performance. It's a constantly moving target.

The exact condition of both the Garn and the WG in my test burns is unknown, except for the fact that neither I nor Deep Portage did or did not do anything to intentionally alter the results. I took both boilers "as is" and in an "as operated condition" at the time of the tests.

 

[Como]

So would the need for a good clean explain the limited burn rate and the build up of coals not allowing continuous burns.

I did a search on the WHS3200 and not surprisingly this thread came up. The other links seemed mainly Alaska focussed, these units I would have thought are more likely to be run continuously or nearly so.

 

[heaterman]

That's quite an endeavor. Thanks for the input. Frankly I hope I never have to have a unit that burns 100# per hour unless I have someone much younger do the work.

AMEN to that!

 

[jebatty]

I understand the focus on the Garn, whether or not there is a need for cleaning, whether or not flue temperatures are higher than they should be, whether or not the Garn can maintain a continuous burn, whether or not on a continuous burn basis it can burn more than 100 lbs of wood per hour, and whether or not on a continuous basis it can output more than about 500,000 BTU's. The Garn is an excellent boiler, it is easy to use, it has a good user following, and it is a solid choice in the mix of available, high efficiency, wood boilers.

Unfortunately, at this time I cannot answer further any of those questions. Deep Portage is not in a situation where it can shut down either of its wood boilers to do any avoidable maintenance. Northern Minnesota is still in full winter, the ground is snow covered, and -11F is in the forecast for Tuesday night, with more snow the balance of the week. I am quite certain that the Garn will get a thorough cleaning and maintenance service this summer after the heating season ends, as will the Wood Gun. Maybe next fall/winter when the temperatures start falling below +10F I will be able to do another test. Maybe in the mean time I will locate someone with the equipment and time to donate to do an accurate flow test. Referrals will be appreciated! And maybe the data will be different.

Then again, maybe not. I have to refer again back to the Garn manual that emphasizes intermittent burns and the need to clean ash between burns. It is apparent that coals to ash do accumulate, that regular ash cleaning is required, and that continuous burn is not the recommended application of the Garn. There must be good reasons for that, and just maybe I learned what those reasons may be. Time and another round of test burns may tell.

Keep plugging away at the report and data. We all will benefit from more knowledge and shared experiences.

 

[heaterman]

and that continuous burn is not the recommended application of the Garn.

Absolutely true!! The basic premise of any storage based system is that the boiler is allowed to fire at full burn to charge the "battery" at peak efficiency and let the building load work from that rather than direct btu input from the fire in the boiler.

The options as I see them for the place you are working with would be to add enough storage to carry them through the night (after addressing other underlying issues) or to go with multiple low water capacity boilers that allow some semblance of full burn under most circumstances. Obviously, staging solid fuel equipment is exceedingly difficult so storage is probably the best route. The system does not care if the storage is Garn based or not. Cycling one or two very high output, low water capacity boilers would definitely raise some problems unless a very high tech boiler with electronic combustion controls were used. Trust me when I tell you that idling a million btu wood boiler is not something you want to do...........

BTW Jim.....how many sq ft are being heated in this place and has there ever been a heat loss conducted to determine what the actual load is?

 

[711mhw]

Jim, what a interesting project. Thank you for filling us in on it. I suspect that this will keep you busy responding for a while.
My question, maybe I missed it in reading your report, but why did Deep Portage decide to use different boilers? Especially two that (in my thinking) are completely different. I don't see much talk here in The Boiler Rm. about the WG, and it seems to out shine the Garn that seems to be the B.R. superstar. Am I misreading your results?

 

[Como]

The WG was my other choice, I think this one is about $25,000? The Garn is a bit more, but to do a proper comparison you need to add storage, even in this flat out situation you would need buffering.

But how many people here run their boilers 24/7?

Actually my first choice was a KoB until I found out their cost/lack of availability.

There is no perfect solution, it all depends.

Sounds like the WG suits this install better than the Garn. Actually several WG's cascaded.

 

[jebatty]

711: ... but why did Deep Portage decide to use different boilers? Especially two that (in my thinking) are completely different. I don’t see much talk here in The Boiler Rm. about the WG, and it seems to out shine the Garn that seems to be the B.R. superstar.

If you inquired of different people, you might get different reasons for the "why." At this point, regardless of the reason(s), Deep Portage is interested in using both boilers in the best manner possible to meet its space and DHW heating needs.

I wouldn't take the route of saying one is the superstar over the other. I see good reasons to pick one or the other, depending on the application. My post is not intended to say one is better than the other.