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raising my boiler temp.

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by leaddog, Nov 2, 2007.

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  1. leaddog

    leaddog Minister of Fire

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    because I have 1300gal storage I wanted to heat my water up to about 195f. My controller on my eco80 would shut down at 80c or 177f. This is a safety feature so you won't overheat it but with that much storage it isn't a problem.
    The solution; I went to RadioShack and bought some 56k resisters. I placed one in parallel with the temp prob. This fools the controller into thinking that the water is about 15f cooler. So now when it reads 80c it is about 195f just where I wanted it to be.
    Easy solution for about $2.00
    Now the down side, The controller now does't turn the circ. pump on until the boiler is about 160f instead of 150 but that isn't a problem.
    On the plus side the boiler gasifies better at the higher temp. I can store more usable btu's in my storage.

    I DON"T recomend you try this if you don't have storage as you could over heat your boiler.
    leaddog

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  2. Nofossil

    Nofossil Moderator Emeritus

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    I toyed with that approach, but I'm going to add a radiant heat zone so that I can get more usable heat out of my storage tank. I think that with a radiant zone for the main floor, I can draw it all the way down to 90 degrees or so. My concerns are that with the higher water temp, I'll lose more heat up the chimney, and there's more chance that I'll be boiling at some spot that's hotter than the point where I'm measuring the temp. Maybe I'm paranoid....

    My storage is only 880 gallons, so I get a day or two of heat at most.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    I want to thank you again for your nozzle-covering trick to essentially cut back your gasifier's output, leaddog. I've been running on one nozzle and it's working really well. I just parked a firebrick over one of the two on my boiler and now basically I've got a 100K btu rig until I get the tank going. I can see you and nofossil like to modify stock equipment, and I'm sure I'll incorporate more of your customization ideas as they pop up.

    I've pondered the boiler temp issue, since I like to run a boiler in the 190 range, and the advantages with hot water storage are clear. But I'm not crazy about running a higher temp than is indicated on the gauge, or in this case, the display. I don't want my boiler running at 195, for example, when the display says 175, for a variety of reasons. So what about doing what you suggest, but while I'm at Radio Shack, also picking up a digital, surface-mount thermometer. The probe could sit right next to the existing controller probe. And you could even mount the new display right over the controller's readout to avoid any confusion. This would give you higher temps and an accurate readout (in Fahrenheit, no less) for probably less than $25.

    I thought about just wiring the blowers through a surface-mount aquastat (why don't they give us some wells on these boilers?), but quickly realized that doing that would eliminate some pretty neat features, like blower modulation at higher temps and the "puff during idle" option to keep the fire going.

    By the same logic, you could even do the other workaround I've heard about, which involves moving the temp probe closer to the return to trick the controller into working hotter, but I like your approach better, as it sounds more reliable, i.e., the differential should always be about the same.
  4. Hbbyloggr

    Hbbyloggr New Member

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    Maybe just a word of caution but 195 is flirting with potential circulator meltdown. My teenage son left the door opened to the furnace after filling it with wood. I later noticed the steam ,smoke and water boiling out of the top of the furnace. Obviously 212 was reached. The next day the two Taco 011 circulators started making noises that got worse and worse. They both had to be replaced. The rotors had dissolved . They were both 4 yrs old at the time and that may also have played into the failure, but in any case I tend to shy away from the real high temps. I keep mine set at 180. What did surprise me though was the Pex tubing held up under the conditions. That could have been a real disaster to replace.

    I keep a link to " Deepvoyage " on Ebay for circulator and wood boiler plumbing parts. He also carries a line of plate heat exchangers. He is located in Conn.

    Hbbyloggr
  5. Eric Johnson

    Eric Johnson Mod Emeritus

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    I ran a Taco 007 for a number of years at temps that exceeded 200 degrees with no problems, and I see that those circulators are have a rated max temp of 240, so that shouldn't be a problem. However, the fact that both yours failed at the same time with the same symptoms tells you something. And I've heard that pex will blow out with hot enough water. I've got a bunch of cheap foam pipe insulation melted to some of my 1" copper from various boiler mishaps in the past. The problem is that if you boiler gets that hot, your natural reaction is to start pumping the water away to dissipate the heat. Unfortunately, that can be at the expense of your other components.

    Running temps approaching 200 is living on the edge, no question about that. A lot less margin for error. On the other hand, I had a boiler once (Marathon) that the mfg. recommended running in the 210/220 range in order to "achieve secondary combustion." I ran it that hot for years, but don't know about the secondary combustion part. In some ways, you can get away with higher temps in a pressurized system because water boils at a higher temp when it's under pressure.

    Contrary to contemporary practice and theory, I like to put my pumps on the return lines because the water tends to be cooler and I think the pumps will last longer. HVAC professionals say that's not necessary with modern circulators and that the most efficient approach is to put the pumps on the supply lines and "pump away" from the boiler. But I'm not an HVAC pro and I do my own work, so I have to do what I'm most comfortable with. Maybe as I learn more I'll modify my approach.
  6. leaddog

    leaddog Minister of Fire

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    Maybe just a word of caution but 195 is flirting with potential circulator meltdown. My teenage son left the door opened to the furnace after filling it with wood. I later noticed the steam ,smoke and water boiling out of the top of the furnace. Obviously 212 was reached. The next day the two Taco 011 circulators started making noises that got worse and worse. They both had to be replaced. The rotors had dissolved . They were both 4 yrs old at the time and that may also have played into the failure, but in any case I tend to shy away from the real high temps. I keep mine set at 180. What did surprise me though was the Pex tubing held up under the conditions. That could have been a real disaster to replace.

    The reason the circ. failed is when the water boiled it created steam and put air into the lines. The circ. are water lubed, no water no lube. They won't last long that way. In the past I learned that the hard way. water got low in my osb. $80 in a heart beat.
    leaddog

    I want to thank you again for your nozzle-covering trick to essentially cut back your gasifier’s output, leaddog. I’ve been running on one nozzle and it’s working really well. I just parked a firebrick over one of the two on my boiler and now basically I’ve got a 100K btu rig until I get the tank going.

    I wish I could take credit for that but it was someone else that posted that. I had thought of it but hadn't tried it until I read it. I've been running that way now for a few days and it makes the wood last longer so when I go out in the morning I have more coals so it starts easier. same btu's just takes longer to get them.
    leaddog
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    That's true about air and circulators. I had one fail once (I suspect running on low water) and when I removed the pump, pieces of bearing came pouring out of the opening.

    I guess we both owe a debt of gratitude to the guy who described how to cripple a gasifier into submission.

    I will quibble with one point: If it takes two hours to generate 200K btu, then you're basically running a 100K btu/hour boiler. I liken it to putting a .75 gpm nozzle on an oil boiler that was running a 1.5 gph nozzle. Does that make sense?

    Obviously, an EKO 60 running on only one nozzle is not going to behave the same way as a unit designed to run on one nozzle, but it's a pretty neat trick for running a big boiler in mild temps without any storage. Seems to me you could make that an interesting option with some kind of adjustable nozzle-control device, but the fact that nobody does, tells me there's more to it than I realize. I can't see where it would hurt the boiler in any event, other than probably a hit in efficiency.

    Slowzuki, nofossil---any of you other gasifier gurus want to tackle that question?
  8. webbie

    webbie Seasoned Moderator Staff Member

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    Lots of regular boilers in the field end up at 195 or 200 because of older sensors, etc.

    BUT, the circs are usually on the return pipe.

    But I have used regular Grunfos on anti-freeze solar loops that also were hot - sometimes over 190, and my circ lasted just about forever.

    I think the problem is probably hit at a higher temp, but it only has to go there ONCE. Also, folks should do the same and use the circ on the return when possible - that way it is usually cooler than the top of the storage or boiler water.
  9. Eric Johnson

    Eric Johnson Mod Emeritus

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    Yeah, the impellers, at least on a Taco 007, are made of plastic. But the spec is 240, so I assume you could go a bit higher without experiencing a meltdown. On the pump, at least.
  10. begreen

    begreen Mooderator Staff Member

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    Maybe no meltdown, but you'd probably experience steam at that temp!
  11. Eric Johnson

    Eric Johnson Mod Emeritus

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    You can certainly "steam out" an Extrol 60 expansion tank. I've done that, too.
  12. Hbbyloggr

    Hbbyloggr New Member

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    Leaddog, I'de say you're on the right track about steam causing the impellers to dissolve, or rather the lack of lubrication . It would make more sense than blaming the higher temperature for the pump failure.

    Of course these things always happen on Saturday night and Sunday when it's impossible to get parts. I now keep two 011's in stock just in case........

    Thanks for the insight.

    Hbbyloggr
  13. Hbbyloggr

    Hbbyloggr New Member

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    Eric,
    Maybe we ought to start up a museum of "experiments gone wrong". Or " Bright ideas test the laws of Physics."

    I also have a thermometer with a mercury column in three segments ,another result of the over fire.
  14. rreihart

    rreihart New Member

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    I'm just about ready to start up my BioMax and I'm interested in the nozzle blocking principle. I don't recall what the loading chamber of the EKO looks like, but I thought it was similar to mine. Any EKO users ever check out the BioMax photos on newhorizon's website? Do you think I can create the same effect? By covering the front or back half of the nozzle opening slot?

    Also a comment on circulator placement. I think circs on the return side is the preferred placement when their are multiple heating units and their is a separate primary loop pump. The "pumping away" I think refers to the primary loop pump away from the expansion tank and not into it. But I am certainly no expert, that's just what I've picked up through reading.

    Thanks, Rob.
  15. Eric Johnson

    Eric Johnson Mod Emeritus

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    What I did, Rob, was to put a firebrick over one of the two nozzles in the firebox and then shut off the air supply to that nozzle. On the EKO, the right air control serves the front nozzle. You might have to play around with the air to get it to work right. I had to open the air control baffle on the front nozzle blower slightly to keep the other nozzle from smoking.

    You will probably have to fool around with the air controls at first, whether you run on two nozzles or one, anyway.

    Also, I've noticed that my boiler seemed to "break in" after about a month of steady use. Some nagging little problems I had at first have basically disappeared--issues related to creosote making the bypass damper stick closed, etc. seem to have worked themselves out. Also, don't be surprised if you get some refractory cracking in the first few weeks of operation. I've got a crack in the cement that fills the gasification chamber door, but a little Rutland Stove Cement took care of it with no problem. I don't know if the circular-shaped refractory mass in the BioMax is more or less prone to cracking, but in my case, once it hit its equilibrium, it stopped.

    And it took me about a month to get the hang of successfully initiating gasification at will. Thought I knew what I was doing, but it pays to get a good, roaring fire in the firebox with the ash door open before shutting everything down and starting the blowers. The more flame you force through those nozzles at first, the faster everything heats up. Makes sense, but I don't always follow the sensible path.

    My point is, don't be discouraged if everything doesn't work exactly the way you expect at first. Once you get the hang of operating these things, they sing.

    Let us know how it goes, Rob. Yours will be our first BioMax road test.
  16. Eric Johnson

    Eric Johnson Mod Emeritus

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    I was thinking about this last night, leaddog. Couple of questions:

    1.) Does your display show the actual temperature, or the lower temp that the controller "thinks" the boiler is at? I'm guessing the latter.
    2.) If not, how do you monitor the actual boiler temp?
    3.) I'm assuming that the controller does everything else the same, just 15 degrees hotter. So when the water approaches the set temp and the blowers begin to modulate, now they're doing it in the low 90s C instead of the high 70s, right?

    As I think I said earlier, I'd be more comfortable if the display showed the actual boiler temp. However, as I think I also said, you could simply mount a remote bulb thermometer over the existing display and accomplish the same thing.
  17. leaddog

    leaddog Minister of Fire

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    1.) Does your display show the actual temperature, or the lower temp that the controller "thinks" the boiler is at? I'm guessing the latter.
    2.) If not, how do you monitor the actual boiler temp?
    3.) I'm assuming that the controller does everything else the same, just 15 degrees hotter. So when the water approaches the set temp and the blowers begin to modulate, now they're doing it in the low 90s C instead of the high 70s, right?

    As I think I said earlier, I'd be more comfortable if the display showed the actual boiler temp. However, as I think I also said, you could simply mount a remote bulb thermometer over the existing display and accomplish the same thing.[/quote]

    No the display shows a false reading that it thinks it is. I have a thermometer At the exit of the boiler.
    And yes it does every thing at a higher temp.

    I wish the controler would have been set up at the factory so you could get actual temp and be able to raise it higher. It now shuts down for low fuel faster and if you don't watch it it might shut down for low fuel if it don't get up to temp fast enough. I would like to just be able to run it with a aquastat and adjust the temp my self. It don't seem that it would be to hard to have made the controler that way. I'm still thinking about that.
    leaddog
  18. Eric Johnson

    Eric Johnson Mod Emeritus

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    I thought about routing the probe power through a surface-mount or remote-bulb aquastat, but I suspect the controller is pre-set, so that probably wouldn't work very well, since it's probably set to respond to actual temp, not what the stat was set at.
  19. WRVERMONT

    WRVERMONT New Member

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    Interesting topic. I've been thinking of somehow raising my boiler output temperature. I have a large storage (1550 gallons). Seems Leaddog has done it. I agree it would be really cool (or HOT in this case) if the temp on the screen was the actual boiler temp. If we could simply raise the target temp (In my case just 3-5 degrees that would be sweet.) Leaddog any idea on what resistor to use for a minor temp adjustment such as this. Thanks for the experimentation.
  20. heaterman

    heaterman Minister of Fire

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    Guys, here's why that happens to any circ when run in those conditions. It's also why you won't have near the circ problems with a closed, pressurized system as you will with an open type.

    If you look up the tech data on any circ, you will come across an acronym called NPSH or Net Positive Suction Head. The NPSH is given a value expressed sometimes in PSI but usually feet of head. In the data there will be a minimum value given at a corresponding flow rate and you will see that as flow increases the NPSH does also. Circs that are designed for high head (long or undersized pipe runs) will require a higher NPSH than a lower head circ. Taco 0011= high head, 007=low head.

    Back to what happens.......... The first thing to understand is that these are circulators, not pumps. A pump moves water from point A to point B and leaves it there. A circulator simply moves the same fluid around a loop by creating a pressure differential in said loop. All these little wet rotor style circs are centrifugal type. The circulating fluid enters the pump casting and is directed to the center of the impeller where the rotation of the impeller causes a pressure drop. The water or fluid enters the vane area of the impeller and due to design, is flung out to the side of the impeller housing. That's the highest pressure area of your system. The water can't bypass in the impeller housing so it must go all the way around the loop to get to the low pressure point of the system.

    Sidetrac ked again.......... The impeller melted because there was not enough NPSH to keep the fluid from flashing to steam. Water boils at 212* under atmospheric pressure but as pressure drops below 1 atmosphere the boiling point goes South along with it. By running the water temp at 190+ you've created perfect conditions for a small steam explosion at the impeller inlet, especially on an open system. A closed system has far fewer problems because it maintains, typically, around 15PSI above atmosheric. Therefore the pressure, even though it's still lowered at the impeller inlet, remains above the minimum required to maintain a NPSH.

    You can't maintain positive pressure on an open system at much above 190 due to the fact that the action of the impeller lowers the boiling point of the water. Again, the higher head the circ is rated for the more critical the system pressure becomes.
  21. leaddog

    leaddog Minister of Fire

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    I used a 56k resister from radio shack. If you could find a 45k that would be better as it would raise it to about 195f at 80c ,but it also changes the other setting so you have to be aware of that and ajust for that. It would be easier if you could change the controler so you could turn it up. Haven't figured that out yet.
  22. hkobus

    hkobus Member

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    Just digging this one up again. I did some measurements on this, and found that the readout will continue to read up to 98*C ( had to stage an overheat to see how long a "no power" event can last with out any issues! :-/ ) after that it goes to 2 dashes on the display. This means the controller will actually sense the higher temps, and I did not change the probe in anyway.
    Now without any circuit drawings, it would be hard to say, and maybe some more experienced techs may want to look at this, but what if one would change out the pot that sets the temp with a lower resistance or add a resistor in parallel to the existing one? Would that also control the high cutout? Or is there an other area on the board for that.
    When things warm up a bit here I may pull the controller again and do some digging, but for now have some more thoughts or better knowledge on this.

    Henk.
  23. Eric Johnson

    Eric Johnson Mod Emeritus

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    First off, heaterman, thanks for that excellent description not only of what a circulator is and how it works, but the role played by system temps and pressure, and as they relate to pressurized vs. open systems. You put a lot of very useful information into a couple of short paragraphs, and I learned a lot of stuff that I should have known already. Exhibit A: Thank God for system pressure, or I would have trashed my nice Grundfos 26-96, I think, during a couple of mishaps with my old Royall boiler.

    Henk: I may be wrong, but doesn't the EKO controller work entirely off that one probe at the top of the boiler? I believe the temp readout is whatever that probe measures it to be. Therefore, if you relocate or cover the probe in a way that fools it into thinking that the boiler is actually cooler than it is, the display will read, say, 80, but actually be, say, 90.

    That seems to be to be a rather crude way of making the boiler temp go higher.

    I admit that I don't really know what a resister is or how you would hook one up to do what you and leaddog are suggesting. Can you expain that to me?
  24. leaddog

    leaddog Minister of Fire

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    I think I understand what you are saying. If you could change the controler so you could set a higher temp and not change all the other functions that would be ideal. The controler will read higher but you can only set 80c for a high limit. When you fool the controler using a resister you change all the other functions and that isn't the best way. Sure wish I had a good drawing and was still working and I would Have taken to work and had some of my good electrition friends work this out. It should be an easy fix. Has any one seen a drawing?
    Leaddog
  25. Eric Johnson

    Eric Johnson Mod Emeritus

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    Must be a Euro thing. They seem paranoid about overheating (hence the threaded connectors on the sides), but the boilers are installed in Europe, as I understand it, nonpressurized. So that's a little weird. Any U.S. boiler I've ever seen goes to 190 or better--usually depending on how the Honeywell stat is set. But as heaterman pointed out, a nonpressurized boiler should run at lower temps anyway, so maybe that's why they max out at 80 (175). I know a lot of OWBs go 190 or better, and most of them are nonpressurized.

    So much to learn; so little time.
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