I've been following this forum while working with John Siegenthaler to design an online course about designing hydronic-based biomass heating systems. I'd love to hear best practices from forum members. What are some of your techniques and strategies for designing and installing biomass heating systems? My hope is to share feedback with our audience of learners at HeatSpring (heatspring.com). Thanks!
Designing Hydronic-Based Biomass Heating Systems - Best Practices?
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BoilerMan
Minister of Fire
Welcome, and I'd love to give Siggy some material, he is one of the masters in hydronic design.
1. Pumping away is still the best practice no matter what some have said about steam flashes and pump cavitation.
2. Pitching the boiler up slightly toward the supply helps with any air released by near boiling conditions.
3. The heat needs to go somewhere, a dump zone is critical, best if done by gravity via a line voltage N.O. magnetic ZV.
4. Staged dump zones work well if someone puts too much fuel in firebox, and thermal storage (if used) is charged.
5. Return protection is also critical or else someone is going to have a huge mess of a tarred up boiler.
6. Thermal storage makes everything work better and prevents the dreaded cycling of solid-fueled combustion.
7. Near boiler piping needs to be metal PEX has no place within 15' or more from the boiler due to boiling potential.
I'm sure most, if not all of this is not news to you but I had to say it in no particular order.
Taylor
1. Pumping away is still the best practice no matter what some have said about steam flashes and pump cavitation.
2. Pitching the boiler up slightly toward the supply helps with any air released by near boiling conditions.
3. The heat needs to go somewhere, a dump zone is critical, best if done by gravity via a line voltage N.O. magnetic ZV.
4. Staged dump zones work well if someone puts too much fuel in firebox, and thermal storage (if used) is charged.
5. Return protection is also critical or else someone is going to have a huge mess of a tarred up boiler.
6. Thermal storage makes everything work better and prevents the dreaded cycling of solid-fueled combustion.
7. Near boiler piping needs to be metal PEX has no place within 15' or more from the boiler due to boiling potential.
I'm sure most, if not all of this is not news to you but I had to say it in no particular order.
Taylor
Last edited:
WmFritz
Member
It's this kind of information that I stay in the Boiler Room. I know for most of you, this stuff is second nature, but I need constant reinforcement of even the simplest rules. I've managed to build two hydronic heat systems in the last couple years, with lots of help from you guys.
Other than basic hydronic "rules" which apply to piping anything regardless of fuel source........ here's a few to start with
1. Minimum of 7 gallons of thermal storage capacity per every 1,000 btu's of boiler output. (This could also be defined as xxx gallons per cubic foot of fire box capacity)
2. Moisture content of fuel no greater than 25%, preferably 20%.
3. Install at least one heating load/zone which incorporates constant circulation with proportional control (think TRV's) (this applies for cord wood or pellets)
4. Mandatory dump zone capable of discarding at least 30% of boiler output in a no power situation. This should be connected directly to the boiler or near boiler piping, not storage.
5. As much as possible, design the heat emitter part of the system to supply adequate heat with 140* water temps or less in order to take full advantage of thermal storage.
1. Minimum of 7 gallons of thermal storage capacity per every 1,000 btu's of boiler output. (This could also be defined as xxx gallons per cubic foot of fire box capacity)
2. Moisture content of fuel no greater than 25%, preferably 20%.
3. Install at least one heating load/zone which incorporates constant circulation with proportional control (think TRV's) (this applies for cord wood or pellets)
4. Mandatory dump zone capable of discarding at least 30% of boiler output in a no power situation. This should be connected directly to the boiler or near boiler piping, not storage.
5. As much as possible, design the heat emitter part of the system to supply adequate heat with 140* water temps or less in order to take full advantage of thermal storage.
A. Resulting from experience with a major professional design failure, best practices include a design and install which must match the btu output required to be moved from the boiler to the application, and this requires a thorough understanding, as related to boiler output and/or btu demand of the system, of required flow rate, pump head, size of piping, and capacity of the circulator.
I learned this first the hard way when I self-installed my Tarm boiler and diligently followed a design schematic. I first used 40 feet of 3/4" pipe and a common small circulator and wondered why my boiler frequently idled. It took awhile to understand why: the flow rate required to move 140,000 btu at delta-T=20 created pump head in excess of the capacity of the circulator, and my actual flow rate with the circulator was far less water than was required, thus the idling boiler. The fix was replacing the piping.
I encountered the same design and implementation failure in a subsequent professional design. My discussions with professionals tend to show a lack of understanding of this issue and the knowledge to deal with it.
B. Ditto Heaterman's minimum 7 gallons/1000 btu output. Again resulting from a major professional design and install failure, and also from the boiler manufacturer's recommendation, a design and install which provided no thermal storage for a 500,000 btuh output boiler. The fix obviously was adding storage, in this case 4000 gallons of thermal storage was added.
C. Resulting from another professional design failure, not understanding the relationship between boiler btu output and delta-T from the system/thermal storage return, and implementing a design which resulted in very warm water being returned to the boiler when much cooler water from thermal storage was available, and therefore boiler idling in a system with substantial thermal capacity still available; the result also being inability to use available thermal storage. The fix was an expensive re-plumbing of the system.
I learned this first the hard way when I self-installed my Tarm boiler and diligently followed a design schematic. I first used 40 feet of 3/4" pipe and a common small circulator and wondered why my boiler frequently idled. It took awhile to understand why: the flow rate required to move 140,000 btu at delta-T=20 created pump head in excess of the capacity of the circulator, and my actual flow rate with the circulator was far less water than was required, thus the idling boiler. The fix was replacing the piping.
I encountered the same design and implementation failure in a subsequent professional design. My discussions with professionals tend to show a lack of understanding of this issue and the knowledge to deal with it.
B. Ditto Heaterman's minimum 7 gallons/1000 btu output. Again resulting from a major professional design and install failure, and also from the boiler manufacturer's recommendation, a design and install which provided no thermal storage for a 500,000 btuh output boiler. The fix obviously was adding storage, in this case 4000 gallons of thermal storage was added.
C. Resulting from another professional design failure, not understanding the relationship between boiler btu output and delta-T from the system/thermal storage return, and implementing a design which resulted in very warm water being returned to the boiler when much cooler water from thermal storage was available, and therefore boiler idling in a system with substantial thermal capacity still available; the result also being inability to use available thermal storage. The fix was an expensive re-plumbing of the system.
Mike Fromme
Burning Hunk
A wood boiler will obey the laws of physics whether or not the installer understands them.
maple1
Minister of Fire
BoilerMan
Minister of Fire
And that is the point. A needed best practices is salesman, manufacturers, installers and professionals who understand these laws and don't mislead consumers. Unsatisfactory installs, or even failed installs, give biomass and other alternative hydronic energy a bad reputation as not working and too complicated.
Documentation should include clear diagrams showing intended system operation (valve states, pump states, and flows) for each operating mode. When something goes wrong, trying to reverse-engineer a poorly documented design is a real problem.
Initial design assumptions and calculations (heat load, delta T, etc.) should also be part of the documentation package. If they were right, then they're a valuable reference. If they were wrong, they're a valuable clue as to why the system might not meet expectations.
Initial design assumptions and calculations (heat load, delta T, etc.) should also be part of the documentation package. If they were right, then they're a valuable reference. If they were wrong, they're a valuable clue as to why the system might not meet expectations.
excellent suggestion. It's so easy to create wiring and piping schematics, plenty of free programs available, and manufacturers components stencils.
Both wiring and piping should be on paper before the first tool is pulled from your toolbox.
Sizing would be my pet peeve. Pumps, pipes, valves, tanks, heat generator and heat emitter
Let me suggest LucidChart as one of the free ones. It's a Google Apps plugin that's free for drawings of moderate complexity. Pretty easy to use, lots of symbols even in the free version. Here's an example of a GUI that I did for a Malt House (Yes, Vesta now helps make beer!):
![[Hearth.com] Designing Hydronic-Based Biomass Heating Systems - Best Practices?](/talk/proxy.php?image=http%3A%2F%2Fwww.nofossil.org%2Fimages%2Fmaltgui.png&hash=636c34f9b623e775b05464cd600af94a "[Hearth.com] Designing Hydronic-Based Biomass Heating Systems - Best Practices?")
Jim that is exactly the thing that so frustrates me about the alternative fuel industry. It is such a valuable resource but it is so poorly represented by most purveyors of this type of equipment. Not only have many manufacturers propagated myths that we will deal with for a generation, but they have stalled, balked at and otherwise dragged their collective feet in embracing sound engineering and principles of operation which maximize the energy production solid fuel is capable of.
They have also done a tremendous disservice to the industry by allowing their products to be distributed and sold by any warm body with a pulse and cash. I have heard things from the mouths of these salesmen that make my hair stand straight up and keep me awake at night. They are either outright liars or completely ignorant about the fundamentals of heat and hydronics.
The industry will never become "mainstream" until it embraces the idea that a certain level of knowledge and skill is needed to apply these appliances correctly. There is no cookie cutter approach to hydronics as every system presents its own set of circumstances. Manufacturers have pushed a basic model or package and led people to believe that the same things will work for any situation. (500' runs of 1" pex to deliver 150,000 btu's comes to mind) Just install a bigger pump...........
The supply chain needs to be cleaned up, or maybe cleaned out is a better phrase. Installers must become educated about the issues presented by the product and the fuel, and they must be professional in the application of the same. Unless those things happen, the solid fuel industry will be stuck in a swampy backwater no one but the EPA pays any attention to.
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