Have you ever drooled to have a date with two beauties in one weekend? I have and it came true the weekend of February 18-21, 2011. The director of Deep Portage, a 56,000 square feet educational institution located near me, handed me the "keys" to the boiler room housing side-by-side a Garn WHS3200 and Wood Gun E500 and let me take the controls. Friday afternoon and an all-nighter with the Wood Gun and Sunday afternoon and another all-nighter with the Garn. The weather forecast was perfect for both periods, with temperatures to range between -5F and +15, to run each separately through its paces, pedal to the metal.
A few days prior I placed an additional seven data logging sensors to supplement the four previously placed, plus one additional sensor that I could move around as the burns were in progress to measure another point of interest that might show up. All was "go" on Friday.
Real World – No Laboratory Test
These boilers were operated in a real world, working environment, using good wood, hopefully like any gasification boiler owner would do. The exceptions were the method of determining how much wood per burn and how frequently the boilers should be fired, together with collection of data. As a practical matter, after showing and discussing my burn procedure with the staff ordinarily responsible for tending the boilers, they did pretty much exactly what I did. One staff member looked at a 100 lb pile of wood, counted the splits, and said that’s just about the same amount he puts in the boiler when he loads it.
Deep Portage on “Low Occupancyâ€
Deep Portage was on low occupancy the test weekend, meaning no use other than by resident staff and minimal administration. Space heating demand and boiler assisted DHW were minimal. The test of these two boilers was not for the specific purpose of seeing how each would meet Deep Portage needs; rather, the test is better characterized as simply putting each boiler through its paces. I believe the Deep Portage heat load is sufficient to take the entire capacity, and probably more, of each boiler separately and, depending on outside temperature, probably greater than both boilers together could meet on a full occupancy and full DHW demand scenario.
The Boiler Wood
Deep Portage has “good†boiler wood, large splits about 22" long, averaging about 10 lbs/split. The wood is 75% red oak with the balance birch and a scattering of minor species. I didn’t test the wood for moisture content but assumed 20% based on 1+ years of outdoor, covered seasoning, its appearance, look and feel, and my 20+ year of burning stove wood. In my estimate the wood likely was of higher quality than that used by most gasification wood boiler operators. It certainly was of a quality I would be happy to use in my gasification boiler.
Wood Gun E500
The WG is rated at 500,000 BTUh. I used my rule of thumb for energy in wood of 6050 BTU/lb, 20% MC, and 400F stack temp. I further assumed at least an 80% efficiency of the WG in capturing burn BTU's to water. This meant 100 lbs of wood on an hourly basis, or 484,000 BTUh. 100 lbs of wood was about 10+/- pieces.
Plans are good but the real world often does not see the planner eye to eye. I quickly realized a puzzling anomaly during the burn period. Although I continued with the test burn all night, the final word is inconclusive data on the WG’s performance. I spent several more hours after the burn to analyze and track down the cause of the anomaly, had numerous discussions with the burn staff of Deep Portage, and we now believe we have identified the problem. It relates to a probable plumbing design error and will take some time to correct. So, if the weather cooperates after the problem is corrected, I will do a second test burn.
What I can say, after tending WG for 20 hours of continuous burn at the rate of 100 lbs of wood each hour, is that the WG is very easy to operate, not much different from load, lock and fire. It easily takes 100 lb loads of wood, hour after hour, and each hourly load burns to low-midburn or good coals by the time of the next hourly loading. There is no significant coal or ash build-up. A minor quirk is a metal flap at the top of the firebox door frame, which virtually eliminates any smoke roll-out when the firebox door is opened, but it can get in the way of tossing in the logs. No other quirks or annoyances. A very nice boiler.
Garn WHS3200
This is the big one, with a burn rate of 925,000 BTUh. Using the same rule of thumb for energy in wood as with the WG, this equates to about 185 lbs of wood per hour, or 895,400BTUh, again assuming at least an 80% efficiency of the Garn in capturing burn BTU's to water. However, because one goal was to test both boilers under as identical conditions as possible, I decided to start with 100 lb loads of wood, just as with the WG. Because the Garn was at a start temperature of 130F, I made the first load at 12:30 pm on Sunday of 150 lbs, rather than 100 lbs. All subsequent loads until the last load at 7:30 am Monday, were 100 lbs and made hourly.
The Garn supplies a large plate heat exchanger, which in turn supplies the Deep Portage system. The Garn is unpressurized and the Deep Portage system is pressurized and also has a glycol/water solution.
The Garn has an analog water temperature meter on the front. I recorded the water temperature at each loading. I also had a sensor fixed to the Garn supply line to measure actual water supply temperature. Actual water supply temperature is about 5F higher than the thermometer reads.
The Garn also has an analog stack temperature meter. I don’t know where the stack temperature meter measures temperature, but each burn would result in stack temperature of a little higher than 600F shortly after loading, then would settle down to 450-550F during the bulk of the burn, and by the end of the hour and the time for the next loading the stack temperature would be a little under 400F. I did not have an independent means to measure stack temperature at the point where the stack mates to the Garn.
[continues in Part 2] Part 2
A few days prior I placed an additional seven data logging sensors to supplement the four previously placed, plus one additional sensor that I could move around as the burns were in progress to measure another point of interest that might show up. All was "go" on Friday.
Real World – No Laboratory Test
These boilers were operated in a real world, working environment, using good wood, hopefully like any gasification boiler owner would do. The exceptions were the method of determining how much wood per burn and how frequently the boilers should be fired, together with collection of data. As a practical matter, after showing and discussing my burn procedure with the staff ordinarily responsible for tending the boilers, they did pretty much exactly what I did. One staff member looked at a 100 lb pile of wood, counted the splits, and said that’s just about the same amount he puts in the boiler when he loads it.
Deep Portage on “Low Occupancyâ€
Deep Portage was on low occupancy the test weekend, meaning no use other than by resident staff and minimal administration. Space heating demand and boiler assisted DHW were minimal. The test of these two boilers was not for the specific purpose of seeing how each would meet Deep Portage needs; rather, the test is better characterized as simply putting each boiler through its paces. I believe the Deep Portage heat load is sufficient to take the entire capacity, and probably more, of each boiler separately and, depending on outside temperature, probably greater than both boilers together could meet on a full occupancy and full DHW demand scenario.
The Boiler Wood
Deep Portage has “good†boiler wood, large splits about 22" long, averaging about 10 lbs/split. The wood is 75% red oak with the balance birch and a scattering of minor species. I didn’t test the wood for moisture content but assumed 20% based on 1+ years of outdoor, covered seasoning, its appearance, look and feel, and my 20+ year of burning stove wood. In my estimate the wood likely was of higher quality than that used by most gasification wood boiler operators. It certainly was of a quality I would be happy to use in my gasification boiler.
Wood Gun E500
The WG is rated at 500,000 BTUh. I used my rule of thumb for energy in wood of 6050 BTU/lb, 20% MC, and 400F stack temp. I further assumed at least an 80% efficiency of the WG in capturing burn BTU's to water. This meant 100 lbs of wood on an hourly basis, or 484,000 BTUh. 100 lbs of wood was about 10+/- pieces.
Plans are good but the real world often does not see the planner eye to eye. I quickly realized a puzzling anomaly during the burn period. Although I continued with the test burn all night, the final word is inconclusive data on the WG’s performance. I spent several more hours after the burn to analyze and track down the cause of the anomaly, had numerous discussions with the burn staff of Deep Portage, and we now believe we have identified the problem. It relates to a probable plumbing design error and will take some time to correct. So, if the weather cooperates after the problem is corrected, I will do a second test burn.
What I can say, after tending WG for 20 hours of continuous burn at the rate of 100 lbs of wood each hour, is that the WG is very easy to operate, not much different from load, lock and fire. It easily takes 100 lb loads of wood, hour after hour, and each hourly load burns to low-midburn or good coals by the time of the next hourly loading. There is no significant coal or ash build-up. A minor quirk is a metal flap at the top of the firebox door frame, which virtually eliminates any smoke roll-out when the firebox door is opened, but it can get in the way of tossing in the logs. No other quirks or annoyances. A very nice boiler.
Garn WHS3200
This is the big one, with a burn rate of 925,000 BTUh. Using the same rule of thumb for energy in wood as with the WG, this equates to about 185 lbs of wood per hour, or 895,400BTUh, again assuming at least an 80% efficiency of the Garn in capturing burn BTU's to water. However, because one goal was to test both boilers under as identical conditions as possible, I decided to start with 100 lb loads of wood, just as with the WG. Because the Garn was at a start temperature of 130F, I made the first load at 12:30 pm on Sunday of 150 lbs, rather than 100 lbs. All subsequent loads until the last load at 7:30 am Monday, were 100 lbs and made hourly.
The Garn supplies a large plate heat exchanger, which in turn supplies the Deep Portage system. The Garn is unpressurized and the Deep Portage system is pressurized and also has a glycol/water solution.
The Garn has an analog water temperature meter on the front. I recorded the water temperature at each loading. I also had a sensor fixed to the Garn supply line to measure actual water supply temperature. Actual water supply temperature is about 5F higher than the thermometer reads.
The Garn also has an analog stack temperature meter. I don’t know where the stack temperature meter measures temperature, but each burn would result in stack temperature of a little higher than 600F shortly after loading, then would settle down to 450-550F during the bulk of the burn, and by the end of the hour and the time for the next loading the stack temperature would be a little under 400F. I did not have an independent means to measure stack temperature at the point where the stack mates to the Garn.
[continues in Part 2] Part 2
