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EKO 80 overheating

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Bill the Dog, Feb 10, 2012.

  1. Bill the Dog

    Bill the Dog Member

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    I've been fighting an overheating problem in my EKO 80 for about a month now. I've melted two controllers (at $200 a throw) now and three temperature probes. It happened again last night. I have the EKO run water through LogStor from a detached garage underground to my basement where it goes to a side are DHW and a heat exchanger in my FA furnace, then back to the boiler. As the water exits the boiler, it passes a temp/press gauge, through a Taco air separator, through a ball valve, through a Danfoss temperature valve and then through a Taco 10 pump that circulates water to my house and back. The return water comes back and goes through a Taco 10 on the backside of the boiler (2 total pumps in my system).
    Last night it seems that the house was not receiving any hot water from the boiler as the FA fan was pushing cold air. When I went out to the boiler, it was overheated, blowing steam out the safety valve, the temp/press gauge showed about 250 F and the temperature probe on the controller was melted. The boiler was HOT.

    The way I see it either my pumps aren't pumping or the Danfoss temperature valve is not allowing hot water out of the boiler loop and into the house. Could my Taco Air separator be the problem? How do I know if my pumps are actually pumping. They are definitely "on" as I can feel them running, but are they actually pumping water.

    By the way, this has happened now about 3-4 times. I have put everything back together and the system runs just peachy for several days and then all of a sudden the overheat issue is back with a vengeance.

    Any help would be greatly appreciated.

    Bill the Dog

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  2. taxidermist

    taxidermist Minister of Fire

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    Bill,
    How big is the pex in your logstor?

    How long of a run do you have

    You say you run thru a danfoss then to the house? the danfoss should be on the return from your house tot he boiler.

    2 pumps wow your boiler is big but not that big.

    We will start there.

    Rob
  3. bpirger

    bpirger Minister of Fire

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    There are flow sensors and all that jazz you could install, but I'd think monitoring the temperature inside the house should tell you if water is flowing. Temp is low, there's no flow. Perhaps a sensor could be rigged up with an alarm using an a419? At least it might alert you of the pending problem. Perhaps this control could also be used to turn on another pump through a "safety loop" somewhere as well....to prevent the meltdown.
  4. Is this a new system? Or an old system with a new problem?

    What do you have the setpoint for the boiler set at?

    Sounds to me like the pumps are not moving water... A diagram would be helpfull.
  5. stee6043

    stee6043 Minister of Fire

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    The first thing that jumped out at me was the statement regarding your Danfoss valve being on the supply side. This would suggest a plumbing issue with your setup. Your supply should not go through a Danfoss valve. Your return should go through the Dafoss with a tee'd line coming from the supply side.

    How long is your run of pex? Why do you have a pump on both supply and return sides? If you're boiler is within a quarter mile of your house I don't think two pumps is really necessary.

    And please....please don't tell us you have 1" pex lines on this boiler. The boiler gods cry every time someone posts here with undersized plumbing. And you have a monster of a boiler in terms of output.
  6. pwschiller

    pwschiller Member

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    Where are your expansion tank(s) attached?

    From Modern Hydronic Heating:
  7. woodsmaster

    woodsmaster Minister of Fire

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    Do you have any storage. That is a huge boiler for one house. Do you have a large heat load?
  8. taxidermist

    taxidermist Minister of Fire

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    Any new news for us Bill?............ You cant bring the crack out and set it in front of us and tell us" wait until i get back to smoke it" !!!!!!!!! LOL



    Rob
  9. in hot water

    in hot water New Member

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    maybe you have some air in the piping, do you have valves located so you can flush all the air out. A good means to power purge.

    hr
  10. steam man

    steam man Minister of Fire

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    It seems as if your stalling the flow when the water temp gets high. I wonder if the supply side taco 10 being a high flow pump gets air bound when the temp gets too high at the suction. The expansion tank statement above may have some merit. I'd almost eliminate that pump and see what happens. Sounds like you may have to slow the circulation down.
  11. maineDIY

    maineDIY New Member

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    It seems as if your stalling the flow when the water temp gets high. I wonder if the supply side taco 10 being a high flow pump gets air bound when the temp gets too high at the suction. The expansion tank statement above may have some merit. I’d almost eliminate that pump and see what happens. Sounds like you may have to slow the circulation down.

    At what temps does that happen (stalling the flow, air bound) ? I feel that at higher temps that might be happening to my setup. The outlet temps are near max and the inlet is much lower ie. inlet:160 outlet:190 range and it doesn't seem to be heating up storage like it should even when there is no call from the zones. It does make sense since when the water is near boiling, even with pressurized storage, it wouldn't take much reduction in pressure/suction (pump vacuum) to creat an air or steam vapor lock. How does one avoid that? Just use a smaller, lower capacity pump. That is certainly counterintuitive-----use a smaller pump to increase flow!
    GG
  12. steam man

    steam man Minister of Fire

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    Anytime you lower the pressure i.e., at a pump suction and raise the temperature of the fluid you will flash the fluid into steam at a certain point. The higher the temperature you need higher pressure to keep from flashing or "cavitation". At some point you will just have vapor in the eye of the pump and it just won't work. I am using my experience with a positve displacement pump that can pull hard and create a vacuum in the suction line. I've seen a number of pumping applications where the fluid was so hot it couldn't be pumped because it would flash at the lower pressure. Having the expansion tank at the suction inlet would kind of even out the pressure variations and should prevent that problem. Check out http://www.mcnallyinstitute.com/11-html/11-12.html for info on net postive suction head calculations. I am not a hydronic guy but the theory is the same. I especially like the statement about flow velocity: Liquid velocity is another important concept. As a liquid's velocity increases, its pressure (90° to the flow) decreases. If the velocity decreases the pressure increases. The rule is : velocity times pressure must remain a constant. This made me think of the Taco 0010 circs your using. Without looking I believe they are a pretty high flow circ. Have you actually calculated the flow rate through your system?

    Also look at the vapor-pressure chart: http://www.mcnallyinstitute.com/Charts/Vapor_Pressure_Chart.html. It tells you at what temperature and pressure a fluid will flash at. Decrease the pressure and at a lower temp the fluid will flash. If you could measure the temperature of the water and the measure the pressure in at the suction side you could tell if it was flashing. One thing you could try is to lower the set point temp of your boiler. If the circ has a discharge valve you could close in on it to lower the flow a bit though not too much.

    I think you're going to have to do some flow calculations to see if everything is in balance. Let us know how it turns out.
  13. Tennman

    Tennman Minister of Fire

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    I'm certainly not the most experienced here, but I'll give what the Taco TD10 data sheet computed for my system. The 0010 per Figure 1 of the TD10 would appear to me to WAY undersized to transfer the energy capacity of an 80. I'll use my 60 sized boiler system as a point of reference. My boiler to HX and back run is ~340 ft. By the time I add in the number of tees, elbows, and ball valves the computed equivalent piping length is 470 feet which including the k, c, and f factors from the data sheet results in a head loss of ~27 ft. So... to move my MUCH smaller assumed energy output of 180kbtu/hr (~85% of the 205 rated) I must have at least 12 gpm. From Figure 1 of the TD10 that puts my 60 system with 1 1/4" pex and a 0013 right on the edge with a flow velocity of 4.4 feet per second which is above the recommended velocity. In other words, given the length of my run and fittings I really should have used 1 1/2" pex to get the flow velocity down, but I was too cheap! Fortunately my system works well but the velocity in my lines is less than idea.

    So to summarize my smaller system compared to yours:

    My average output assumption of my 60 class boiler = 180k btu/hr (~85% rated output, maybe high)
    Equivalent piping length = 470 ft
    Head Loss = 26.9 ft

    Bingo... per TD10 Figure 1 = Taco 0013 for my system which is a WAY bigger pump than what your using for a boiler WAY bigger than mine. If you want provide me with your lengths and the approximate number of tees and elbows and ball valves in your circ system and I'll put that in my spreadsheet which will spit out the Taco recommended pump per TD10. With special emphasis on THE TD10 RECOMMENDED PUMP. Not based on my system experience base of 1. Google Taco TD10 data sheet to see all the above. I just built a spreadsheet to make it easier for me.
  14. steam man

    steam man Minister of Fire

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    I like your write up. Sounds like you have it done pat. However, based on what Bill the Dog said about his blower just blowing "cold air" leads me to believe nothing was flowing in those lines thus the overheating issue. Also, it seemed to have worked at times moving heat. Also, why the boiler just doesn't shut off at set point temp is odd. Since he has "two" pumps essentially in series I am not sure how you figure the flow characteristics. To me even if the load was slow to remove heat due to to piping issues, heat exchanger, etc.. the boiler should still shutdown at boiler temp.

    Anyone know what the system pressure should normally be when cold in this setup?
  15. stee6043

    stee6043 Minister of Fire

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    I'd bet ole Bill is not coming back. It seems every now and again folks will pop up and try to get us to tell them what they want to hear (the easy answer) but when they don't get that, they move along.

    I know if I dropped this kind of coin on a system that isn't working and/or was not installed correctly I'd definitely have a "denial" reaction initially...

    If I had to wager a guess our friend Bill has a 1" pex run installed on his EKO 80. It also sounds like he may have some plumbing "oddities" at his boiler bypass loop, including the use of two drastically oversized pumps. What does all of this mean? It means this is likely going to be a very expensive "fix".
  16. Tennman

    Tennman Minister of Fire

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    You're right Steam, I guess I should have re-read his original post because I forgot some of his symptoms. Two pumps in series strikes me as odd, but maybe somewhere in the boiler world that is normal? A call to a Taco Technical guy would be interesting to see what is the result of having two pumps in series. I can imagine how having another impeller pump could provide additional head pressure, but not clear since the motor rpm is fixed if you'd get more gpm. Regardless, you're right cold air means really screwed up circulation. He may not be getting all his output energy, but the TWO Taco 10's should be delivering some. I'll be interested to find out if the professionals here routinely see pumps in series. I also just re-read Stee's comment about the location of the Danfoss. Some really different stuff going on here. You out there Bill? Inquiring minds want to know more.
  17. Chris Hoskin

    Chris Hoskin TarmSalesGuy

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    assuming it is installed correctly (unknown) the Danfoss could be air bound.
  18. pwschiller

    pwschiller Member

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    From Modern Hydronic Heating:
    For example, a Taco 008 pump curve crosses the following points: 0 GPM @ 15.2 Feet, 10 GPM @ 8 Feet, and 14.6 GPM @ 0 Feet. The pump curve for two 008's in series would cross through 0 GPM @ 30.4 Feet, 10 GPM @ 16 Feet, and 14.6 GPM @ 0 Feet.

    Where your system resistance curve crosses the new pump curve will give you your feet of head and flow rate.

    If there's been significant cavitation at one of the pumps, it should probably be checked out to make sure it's not damaged.
  19. steam man

    steam man Minister of Fire

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    Wait a minute! "For about a month now"? I have to ask if this was working before but just in the last month or since you installed it? You may have a pump screwed up, especially the hot side. I'd take a look at that impeller.
  20. Bill the Dog

    Bill the Dog Member

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    Hi all,
    I'm still here and still having the problems. Since I posted the original message, I've replaced the thermostat valve in the Danfoss (as per a conversation Dave at Cozy Heat and I had a while ago). The overheating problem came back three days later, but at least now my house is always receiving hot water from the boiler. Kind of like I solved one problem, but I still have another to solve. I cleaned out my entire boiler, including pulling the turbulators and cleaning ALL of the ash and creosote out from everywhere and putting everything back together. I did this just because I thought that maybe my bypass had some creosote buildup and was not closing all the way. It's definitely closing now and my turbulators and heat exchangers are very clean.
    Now, I am getting hot water to my house all the time, but the boiler still overheats (controller error message #2 and sometimes #3) every 1-3 days. The most recent time (a few days ago) my wife discovered the overheat error and noticed that the bypass valve was open. I know that I closed it when I left the boiler. I do know that a few times in it's history, my boiler has "huffed" and pushed the bypass open. Can an open bypass lead to overheating? I would guess it would make it more easy for the upper firebox to pull air through the fan openings even thought the controller has the fans turned off. This is a guess. I simply don't know.

    I'll try to do a better job soon with explaining my plumbing setup. I do know that I have 1 1/4 or 1 1/2 inch PEX on my run to the house and all of the PEX inside the house. I'll double check to nail that down.
    I'll see exactly where the two pumps are placed. I know I should know off hand, but I forget if one of the Taco 10s is on the return side or the supply side. The return and supply pipes run right next to one another and I forget which one is which unless I'm standing in front of them. The other Taco is on the return side of the boiler loop and is actually right on the back of the boiler. Again, I should know all this stuff, but I installed it 4.5 years ago and I've forgotten exactly what everything is and how it's connected.
    I should also make sure everyone knows that this boiler and plumbing setup has worked flawlessly for 4 years until this recent problem. I am not just jumping in here as a newby and jumping back out. I've been on the forum for over 12 years dating way back to my old indoor catalytic stove days. I don't post often as I am nowhere nearly as knowledgeable as the experts that hang around most often. I generally just read the articles when I have time and leave it at that. Also, I'm just really busy with a ton of other stuff so that I don't check back in as often as most people.

    Thanks for any and all help.

    Bill the Dog
  21. Tennman

    Tennman Minister of Fire

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    Geez Bill... my inexperience is exactly why I post here often.... Because I ain't nearly as knowledgeable as the experts here.

    FYI... I was going to start a post about getting a quieter pump. Well crap... I thot just sticking the expansion tank ANYWHERE would handle expansion... right?? I've got mine about 200' downstream of the pump after the HX in my root cellar. I just read what Pete posted: "Always place the circulator so that its inlet is close to the connection point of the system’s expansion tank." Duh. I had no idea.

    So thanks Bill AND Pete.... We may not have fixed your problem yet, but you may have fixed mine.

    BTW, just some rough numbers from the TD10:
    275,000 btu/hr x 75% = 205,000 btu/hr
    Per TD10:
    if your system was designed for a 20 deg F drop across the HX you need ~ 20.5 gpm
    if your system was designed for a 30 deg F drop across the HX you need ~ 13.7 gpm

    So, by having two pumps in series it looks like as long as your head is somewhere south of 18-20 ft the Taco 0010 will push the required gpm. The trick was to get double the head by doubling the pumps in series..... huh. Bottomline, if the pumps are healthy per TD10 they should do the job. Now... I need to re-plumb my expansion tank.
  22. huffdawg

    huffdawg Minister of Fire

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    [quoI was going to start a post about getting a quieter pump. Well crap... I thot just sticking the expansion tank ANYWHERE would handle expansion... right?? I've got mine about 200' downstream of the pump after the HX in my root cellar. I just read what Pete posted: "Always place the circulator so that its inlet is close to the connection point of the system’s expansion tank." Duh. I had no idea.

    So thanks Bill AND Pete.... We may not have fixed your problem yet, but you may have fixed mine.

    What sort of issues were you having with the placement of your expansion tank Tennman
  23. pwschiller

    pwschiller Member

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    I'm by no means an expert, but I did borrow a 1st edition of John Seigenthaler's Modern Hydronic Heating through interlibrary loan. Even the 1st edition was incredibly helpful.

    I think that the worse place to connect the expansion tank would be close to the pump outlet. I had to return the book, so hopefully I'll explain this correctly.

    When the pump is running, the pressure is greatest closest to the pump outlet and lowest at the pump inlet. I guess you could think of it as the water is being pushed out the outlet and sucked in at the inlet. When you have a piping loop with very high resistance, such as when there are hundreds of feet of PEX connecting two systems in different buildings, that pressure difference between the pump inlet and outlet sides becomes even greater. Let's say that when the pump isn't running the static pressure in the system is 12 psi. When the circulator pump in your 400' PEX loop is running, the pressure could be 18 psi at the pump outlet and 6 psi at the pump inlet. Here's why it matters where the expansion tank is connected: As John Seigenthaler explained it, the point at which the expansion tank is connected is the point of constant pressure, which should be equal (or close to) the static pressure when nothing is running. If you connect the expansion tank close to the pump inlet, the pressure at the inlet is now 12 psi, which is more than enough for the pump to run properly. But, if you connect the expansion tank close to the pump outlet, the pressure at the outlet now drops to 12 psi and the pressure at the pump inlet could be 0 psi. As the temperature of the system increases, the low pressure at the pump inlet becomes even more of a problem, because it brings the water closer to the point at which it turns to vapor, which will result in pump cavitation.

    I'm pretty sure that a couple of my Taco 007's are much noisier now than they were eight years when they were installed. It could also just be your pump.
  24. Tennman

    Tennman Minister of Fire

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    Ok, I'm back. Dodged another series of tornadoes a few hours ago. Here in northern Alabama we just had a series of tornadoes retrace the same track and neighborhoods they did about a year ago. I'm just now fixin' to drive thru devastation again.

    Huff, I wasn't having any issues with my expansion tank, but my pump (I think) is noisy. But then again I have no pervious experience to compare it to. But based on Seigenthaler’s recommendation, my pump's about 190' upstream of the pump or 220' downstream. I can sort of envision how having the expansion tank near the inlet would smooth the flow into the impeller.

    Bill, Just for the discussion's sake, the pressure gage on my boiler exit is always a steady ~12 psi, managed by my autofil. That pressure is not far downstream of the pump output that is not far from the boiler entrance. No idea what the pump supply is, but it's got to be less than that 12 psi after it makes the 400' circuit with all the head losses.

    BTW, does everyone just keep their pumps running all the time regardless of house demand? Taxi suggested I tie my pump on with the fan on which sounds like a good idea except then how does it know about boiler over heating. This is all the byproduct of the thot of moving my noisy pump into the root cellar near the fan control so fan and pump come on at the same time.

    Really off Bill's topic now, but he doesn't seem to mind.
  25. Willman

    Willman Minister of Fire

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    Why are you heating our root cellar?

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