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    First Winter with TT Solo 110 (62 Posts)

  • FPEngineer FPEngineer @ 8:34 PM
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    First Winter with TT Solo 110

    Over the summer, I had a TT Solo 110 installed in my house. We used my existing Boilermate indirect for DHW and 3 zones of fin tube baseboard for heat. Much of the fin tube on the main floor of the house was replaced with high output fin tube to minimize the water temperature needed to heat the house.

    All was well until the fall when we turned on the heat. I expected some short cycling during the shoulder seasons, but observed that the return temperature is always only roughly 2 degrees less than the supply (as measured by the boiler). The house is staying warm so I know that heat is being removed from the water as it is circulated. I suspect that the flow rate through the boiler's heat exchanger is much greater than through my zones and therefore supply water is flowing backward through the closely spaced tees and heating the return water. The internal circulator in the boiler is set to LO and the zone circulators are set to HI (all are Grundfos 15-58s).

    The piping appears to match the schematic in the TT manual. I've attached pictures and am hoping that someone can confirm it is correct or suggest how to fix it.

    Thanks in advance.
  • Chris Chris @ 9:21 PM
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    I'm Blind

    Because I don't see any closely spaced tees. Looks and sounds to me your over pumping the zones. Have you measured actual zone supply and return temperature difference?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Paul48 Paul48 @ 9:46 PM
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    That's

    a problem........If you want to zone that boiler with circulators, it has to be piped P/S. Yours isn't piped P/S.
  • Zman Zman @ 12:25 AM
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    Strange

    What you have is circulators in series. You are way over pumping. I think the right solution is to pipe it primary secondary. It would probably work fine if you removed the boiler circ and set the zones to low.
    Carl 
  • FPEngineer FPEngineer @ 6:26 AM
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    Closely spaced tees

    The closely spaced tees are just below the boiler. This picture should show them more clearly.

    The supply is on the right and the return loops around the back on the left.  The cooper pipe behind the supply is the dedicated supply to the DHW tank.
    This post was edited by an admin on November 30, 2012 7:23 AM.
  • FPEngineer FPEngineer @ 6:39 AM
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    TT Schematic

    This is Triangle Tube's schematic for zoning with circulators that the installer followed.  It appears to be close to how my boiler is piped, although the check valve on the return is missing and the return from the indirect tank does not tie into the same spot as the schematic shows.
  • Chris Chris @ 7:29 AM
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    That is Not

    Pri/Sec piping in the pic. One tee is vertical on the bull the other horizontal..I ask again, have you measured zone supply temp and return temp, not boiler supply and return? Close isn't close enough..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
    This post was edited by an admin on November 30, 2012 7:30 AM.
  • FPEngineer FPEngineer @ 8:08 AM
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    That's what I thought...

    but TT tech support told the installer that it is not a problem because both the supply and return are on the bull so the friction losses are the same.

    I don't have the ability to accurately measure the actual zone supply and return temperatures, but it seems like this information is critical to figure out what is going on.
  • Gordan Gordan @ 8:08 AM
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    I have to disagree...

    While the presence of any elbows between the closely spaced tees, the distance between the tees, and the sizes of all the pipes matter to the pressure drop (and therefore to hydraulic separation) those boiler risers are still at 90 degrees to the main and the main is still a straight run through the closely spaced tees. I fail to see how the angle of the risers to each other could possibly affect the function as a hydraulic separation device.

    I agree with everyone's take on the main issue: almost certainly the zones are being overpumped.
  • SWEI SWEI @ 11:05 AM
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    TT Schematic

    Shows circulators pumping away from the Point of No Pressure Change (expansion tank.)  Your tank appears to be on the return side of the circs.

    Fixing this will require a re-pipe -- a perfect opportunity to replace those zone circs with valves, install a pressure-dependent circulator and eliminate the P/S piping altogether.
  • FPEngineer FPEngineer @ 1:59 PM
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    Just seeing this post now...

    You are correct!  My expansion tank is on the boiler supply line that ties into the return to the boiler.  The installer told me that TT tech support told him to install them that way even though the manual shows it system supply piping.
  • clammy clammy @ 8:04 AM
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    Tee spacing

    Even though the p/s piping is right on top (or underneith ) the boiler ,the fact weather a tee on a P/S pipin is hortizontal or vertical in possition makes no never mind except in some cases making it easier to install a check or thermal trap but the issue i see is the distance between the elbow and second tee there should be more straight length of pipe, the ell is to close that piece of pipe should be at least 7 to 10 inches long  . (in photo tee on left ) .I would have all the zone pumps set to low and would have piped it using the perferred  piping method which prioritizes the domestic hot water .This unit has a internal circ correct .
  • FPEngineer FPEngineer @ 8:15 AM
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    Which ell?

    The ell on the return entering the run of the tee(white circle) or the ell turning up back into the boiler (yellow circle)?

    Yes, there is a circulator inside the boiler.
    This post was edited by an admin on November 30, 2012 8:21 AM.
  • Chris Chris @ 8:18 AM
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    Sure It Does

    They are no longer closely spaced in this case.. One is horizontal the other vertical. Looks like 1" pipe which means they cannot be more then 8" or 4 pipe diameters. We know that the spacing between boiler supply and return is 5". My bet is on the tees and over pumping.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • FPEngineer FPEngineer @ 8:51 AM
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    Pipe Size

    The near boiler piping is all 1".  The tees are 5" on center.

    Do you think I'm overpumping through the boiler or through the zones? 

    I think that the flow through the boiler is greater than the flow through the zones because the loop at the boiler is so short and the pipe is 1" and the zones have an elevation loss to overcome plus they are at least 150' of 3/4" pipe.  All pumps are Grundfos 15-58s.  I have the zone pumps set to HI and the boiler pump set to LO in an attempt to balance the flows.
  • Gordan Gordan @ 9:02 AM
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    You're not pumping, you're circulating

    There is no net gain or loss in elevation since the water winds up at the same spot. There is absolutely no benefit to overpumping: if the zones are heating well enough, you have enough flow. Too much flow, on the other hand, has the following disadvantages:

    - unnecessarily high electricity usage (over twice as high at speed 3 as at speed 1 on the 15-58)
    - velocity noise and possible water erosion of fittings
    - return temperatures are now higher for any given heat output and average water temp over the emitter; if you check out what your boiler is telling you you will see that the exhaust temperature is basically identical to the return water temperature, so this means more heat goes out the exhaust and there will be less condensing.

    This is why you need to start low and measure temperature drop across the circuit. If the latter becomes too high and a particular zone is not keeping up any more, it's always possible to bump it back up.

    Surely you have a meat thermometer in your kitchen... use that, in a pinch, if you have no other means of measuring.
  • NRT_Rob NRT_Rob @ 2:04 PM
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    I have no idea

    what chris is on about here. those are closely spaced tees. they do not have to hit the pipe from the same axis. the elbow a few inches away reduces their effectiveness, but the pressure drop between the two tees is practically zero. You are basically hydraulically separated and you do not have any piping problems i can see here.

    even the expansion tank is not a problem. as long as you do not have a significant pressure drop between the suction of the pump and the expansion tank you are "pumping away". Such as in this case.

    you are overpumped. this is why zone by pump systems are not as efficient as zone valve systems. end of story.
    NRT.Rob
  • FPEngineer FPEngineer @ 8:36 AM
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    Flows

    This is my understanding of the flows at the closely spaced tees.  Please correct me if I am wrong.

    Situation #1

    Flow through the boiler is greater than through the zones.
    Zones will see the supply temp from the boiler.  Return to the boiler will be at a mixed temperature produced by the zone return mixing with the supply.  Supply water flows back through the tees toward the return.

    Situation #2

    Flow through the boiler is equal to flow through the zones.

    All supply water is directed to the zone and all the zone return water is directed back to boiler.  There is no flow between tees.

    Situation #3

    Flow through the zones is greater than flow through the boiler.

    Zone return water mixes with supply water to produce a mixed temperature water that is sent to the zones.  The boiler receives water at the return temperature from the zone.  Flow between tees is from return toward the supply.

    I believe I have situation #1, however it appears that you guys are suggesting that I have situation #3. 

    I guess I really need a way to accurately measure the temperatures of the pipes to diagnose what's really happening.  Is there a way to use an IR thermometer on copper pipes?  I don't think they work on shiney surfaces.
  • Gordan Gordan @ 8:55 AM
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    So it's like this

    Yes, your understanding is correct, but there's still one thing missing, which is the consideration of overall flow through the system - not just relative to boiler flow.

    If the flow through the system is too great, for any given heat output the temperature drop through the circuit will be small. So, regardless whether you were in scenario 1, 2 or 3, you would see a small temperature drop between boiler supply and boiler return.

    By the way, please tell us you're using outdoor reset. :-)
  • FPEngineer FPEngineer @ 9:11 AM
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    Outdoor Reset

    Yes, I am using the outdoor reset.
  • Paul48 Paul48 @ 9:14 AM
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    Situation #1

    What you have created is a boiler by-pass, which is what you would do with a cast-iron boiler to minimize condensing.You are failing to take advantage of TT's heat exchanger with its low resistance to flow, and run off its internal circulator with zone valves. This eliminates the problems you have created.
  • Jason Jason @ 8:55 AM
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    Tees

    The rotation of the tees is irrelevant providing the run of the tees is on the primary pipe. The branch's must go to the boiler. More importantly is the distance between the tees and pipe distances before and after the tees. You should keep the tees as close as possible. The rule is maximum 4 times the diameter of the primary pipe (run of tees) not to exceed 12". This means if you have 1-1/4" pipe that would be 5" between the centerline of the tees. You do not have the option of 5" to 12". The 12" only comes into play when the 4 times rule exceeds 12". Than the tees need to 12" or less. Keep them as close as possible.
    The distance before the tees is 8 times the pipe diameter minimum and after the tees is 4 times the diameter of the pipe minimum.
    Turn your system pump speeds down, try the lowest speed first. The faster the water flows the lower the delta-T. Slow the water down the greater the delta-T.
    Most systems zoned with pumps have too much flow.
  • Chris Chris @ 9:03 AM
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    That is My Point

    The distance of those tee's because one is horizontal and one vertical exceeds the proper distance I fee in this case. I'm not there but it is something I would be double checking.

    We all know the zones are over pumping.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • FPEngineer FPEngineer @ 9:19 AM
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    Overpumping

    Can I use the valves on the return to throttle down the flow on the zones?
  • Gordan Gordan @ 9:24 AM
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    Let me get this straight...

    You want to leave the circulators on max speed but use the ball valves to throttle flow? What would be the point of that?
  • FPEngineer FPEngineer @ 9:34 AM
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    I've set the circulators to LO

    Per everyone's input here.  I still don't see a difference in the return temp so I'm asking if I should try throttling them down further.
  • Gordan Gordan @ 9:47 AM
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    Oh, I see... I didn't catch you mentioning that

    No, I wouldn't do that without first measuring temperatures on the zone supplies and returns. And letting things come to a new balance. It takes a while for all the thermal mass in the system to adjust to the new normal.

    If the temperature drop across the zones is still too low after you give it time to come down, you might try throttling. Be aware, though, that ball valves aren't made for that purpose; they don't really start throttling until they're nearly three-quarters closed, and then things get pretty touchy. Without flow gauges, it's difficult to know what's happening, but I guess you could listen for the turbulence across the valve. Any adjustment should be followed by a period of non-tinkering to let the system balance out. I suggest you try this with a single zone only, and MEASURE (did I mention measuring?) the effect on that zone's temperature drop before trying to replicate on other zones. You should ignore the boiler for the time being. You can worry about it after your system is where it needs to be.

    If you find that throttling is necessary on most or all of the zones to get the temperature drop across the zone to a decent level (say, 10 F on a decently cold day) then you might consider ditching zoning with circulators.
    This post was edited by an admin on November 30, 2012 9:49 AM.
  • Paul48 Paul48 @ 9:27 AM
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    P/S

    The thing about P/S piping, is that one circulator doesn't know the other exists. You are probably overcirculating to the system, but you will chase your tail with the problem by adjusting circulation.
  • Paul48 Paul48 @ 9:45 AM
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    Solution

    Check the pump curve for the boilers circulator to ensure adequate flow. Seperate the supply and return at the boiler. Replace the circulators with zone valves and replace the switching relay with a zone valve control.
  • Chris Chris @ 9:53 AM
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    Simpliar Solution

    Install Taco Bumble Bees or Grundt Alphas with no piping or control changes..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • FPEngineer FPEngineer @ 11:44 AM
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    Thanks to everyone for the suggestions.

    I'm still trying to understand why I am having a problem that appears obvious to everyone when the boiler is piped per TT's recommendation.

    Take a look at the attached figure taken directly from the TT instruction manual.  It appears to me that there is a primary loop through the boiler and the zones themselves are the secondary loops.  Every schematic I've seen has a secondary loop with the zones in either series or parallel with it.

    The second 2 attachments show the typical schematics I've seen for P/S piping.  TT even shows something similar to these when using zone valves.
    This post was edited by an admin on November 30, 2012 11:57 AM.
  • Chris Chris @ 12:37 PM
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    Concepts

    Piping diagrams are conceptual.

    It is still the installers responsibility to install the appropriate sized pumps, piping, etc for the system he is working on. Just because the picture shows a pump and you have a pump it doesn't mean your pumps are sized properly for each zones gpm and head requirement.

    Pics 2 and 3 do not apply to your system and Pic 1 shows a radiant manifold that can be individually balanced..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
    This post was edited by an admin on November 30, 2012 12:43 PM.
  • FPEngineer FPEngineer @ 11:03 AM
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    Been away on vacation, but still working on this problem

    The installer was here yesterday and he reconfigured the P/S piping.  The tees are now 4" on center and there is 8" of straight pipe before the tees and 4" of straight pipe after.  All circulators are set to LO.  There is a 1" check valve on the the return to the boiler and the DHW return is piped to the boiler side of the return check per TT's schematic.

    2 issues still remain in my opinion.

    1.  Supply and return temperatures as measured by the boiler are still very close (2 or 4 degrees difference) with only 1 zone running.  With more than 1 zone running, the situation improves to approximately 8-10 degrees as measured by the boiler.  There is approximately a 20 degree delta T as measured across the zones with the pumps set on LO.  This tells me that I am still getting mixing at the closely spaced tees. 

    2.  Flow is still being induced through the DHW loop when the heating zones are running.  Since the setpoint for the heating zones is between 120 and 140 depending on outside temperature, this flow is cooling the water in the tank until it eventually results in a DHW call. 

    Any suggestions for solving these issues?  I believe one person suggested removing the P/S piping and using the TT internal circulator with zone valves for the heating zones.  This makes sense to me, but is it my only option?  I am baffled by the problem with the DHW.
  • SWEI SWEI @ 11:18 AM
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    boiler differential

    Are you measuring on high fire at full load?
  • FPEngineer FPEngineer @ 11:29 AM
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    No

    I am reading the boiler supply and return temperature on the boiler control display.

    I just took some readings with an IR thermometer.  I can't read the copper pipe because of the shiny finish, but I measured the temperature of the red pump body to be 125F and i measure the return before the closely spaced tees at 115F.  The boiler supply and return temps were equal when I made these measurements.

    Based on the BTU output of the zone (6860 BTU with 125F water) and a 10 degree delta T measured across the zone, I calculate a 1.4 GPM flowrate.  The minimum flow through the boiler is 5 GPM so I think this is creating the problem.  3.6 GPM of supply water is combining with the 115F return from the zone at the closely spaced tees.
  • SWEI SWEI @ 11:56 AM
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    boiler differential

    Can be anywhere from 0F to 35F depending on load and circulation rate.  You need to test at high fire under full load in order to see if you are actually over-pumped on the primary. 
  • Gordan Gordan @ 11:30 AM
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    The two problems could be related

    The heat that's drained from the DHW tank has to go somewhere, in this case, likely back to the boiler. It's probably mixing with the system return. The indirect should have been piped from the separate supply outlet that TT graciously provides, and the return needs to be to the boiler return riser. That will ensure that the boiler circulator does not circulate through the indirect.
  • FPEngineer FPEngineer @ 11:49 AM
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    Gordan, see pic

    The supply to the indirect is piped from the TT outlet.  The return from the indirect is piped to the boiler return after the check per TT's schematic.
  • Gordan Gordan @ 12:57 PM
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    My bad

    A picture may be worth a thousand words, but it's best to have both. :-)

    Ok, so here's the checklist:

    1) Boiler pump induces flow through DHW - I think we can safely say this is not the issue.
    2) DHW pump is on outside of a DHW call - is it wired to the proper terminals? Can you check voltage during times that it's supposed to be off?
    3) Gravity flow - are there flow check valves on the DHW supply and return lines? Where are they located?

    How quickly does this loss of heat occur? What's the DHW on/off differential?
  • FPEngineer FPEngineer @ 1:51 PM
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    No problem

    Pictures definitely help! :)

    1.  My thought was that the boiler pump is inducing flow through the DHW loop, however, it seems like everyone using an indirect and the TT Solo 110 would be having this issue.  The DHWR does tie into the return to the boiler between the check valve (CV in pic) and the heat exchanger.  The suction side of the pump is on the discharge of the heat exchanger. 

    2.  DHW is wired per the TT instruction manual and I will verify that the voltage is when it is supposed to be on and off. 

    3.  The DHW Grundfos pump has an integrated flow check on the supply side of the indirect tank and there is a check in the return line also located just before the valve.

    I know without a doubt that there is flow in the DHW loop while the CH zones are running.  If i close the valve after the CV in the DHWR line, all the DHW piping stays cool to the touch.  As soon as I open the valve the DHWS&R lines both get hot.

    The setpoint for the indirect is 136F and it's on a 10 degree differential so it calls for heat when the tank reaches 126F.  The CH setpoint varies with outside temperature but has generally been less than the indirect setpoint (136F).  When the CH is not running, the tank generally loses 1 to 2 degrees per hour.  With 2 or 3 CH zones running, I've observed the tank going from 136F to 126F in as little as 30 minutes.
  • Gordan Gordan @ 2:39 PM
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    I wonder

    I know you said it's connected to the correct terminals, but if you had the DHW circ connected to the Auxilliary Boiler circ terminals, you would see what you're seeing. Quoting from page 33 in the manual:

    4. Connect the Auxiliary Boiler circulator to
    the line voltage terminal strip on the wiring
    panel below the PRESTIGE control module,
    as shown in Fig. 19 on page 31. The
    auxiliary boiler circulator is enabled during
    a CH or a DHW call. This circulator is typically
    used in retrofit applications where
    the CH and DHW systems are connected to
    a common boiler supply.
  • FPEngineer FPEngineer @ 3:20 PM
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    Double checked the wiring

    Everything appears to be correct.  I took some pictures just to make sure, but the DHW is definitely connected to the correct spot.  Nothing is wired to the Aux Boiler terminal.

    One CH zone was just running and I have the valve on the DHWR shut.  Both the DHWS&R lines were cool to the touch.  As soon as I opened the valve, both lines got hot.  I will pay attention next time which direction the heat comes from.  With the checks in the circulator and the return line, I would expect it to flow from supply to return.
  • Gordan Gordan @ 3:45 PM
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    No idea

    Beyond what I've already suggested. The boiler and system circs shouldn't be able to circulate through this, since both the DHWR and DHWS are on the inlet side of the boiler circ and the system circ is off of closely spaced tees. So... check voltage/disconnect the DHW circ and see if it still happens. See if it happens with all circs off and the valves open. If the former, something is wonky with your prestige since it's turning on the DHW circ when it shouldn't. If the latter, you've got ghost flow and need to check your checks.
  • FPEngineer FPEngineer @ 4:39 PM
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    Flow problem through indirect solved!!!

    The installer left the thumbscrews on the DHWR check and the CHR check both open!!!

    I closed them both to allow the flow check to operate and now I don't have reverse flow of return water cooling off my DHW tank!
  • FPEngineer FPEngineer @ 1:54 PM
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    More pictures

    Pictures of the TT Solo 110 without the cover and a closer pic of the internal circulator.
  • BostonGTR BostonGTR @ 4:45 PM
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    Success

    Good job finally locating the problem!
  • FPEngineer FPEngineer @ 5:05 PM
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    Hoping to now solve the issue with the return water temp

    I'm leaning toward zone valves with the entire system running off the boiler circulator.  It seems to me that there is going to be mixing between the supply and return at the closely spaced tees unless the flow is perfectly balanced between the zone circulators and the boiler circulator.  When only 1 zone is running, the difference in flow in the zone and flow in the boiler is so large that the return water is mostly supply being recirculated back through the closely spaced tees.  The situation improves with multiple zones running, however, I'd prefer to keep each level of the house on separate zones.

    What zone valves does everyone recommend if i make the change?
  • SWEI SWEI @ 10:16 PM
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    changing to zone valves

    I'd suggest replacing the internal pump with a pressure-dependent circulator (e.g. WIlo Stratos or Grundfos Alpha.)  Once you do this, you need to change the Demand Type setting from Switch & Setpoint to Constant & Outdoor Reset.
  • NRT_Rob NRT_Rob @ 2:10 PM
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    hold your horses

    if you are going to direct pump this boiler to the zones, you better be sure your smallest zone will take at least 2 GPM, which is the bare minimum TT wants to see going through this boiler to avoid rampant short cycling. 30 dt on minimum fire.

    usually you need a bypass. modulating pumps, not a good idea in this case, unless you are primary/secondary OR very sure your smallest zone has adequate minimum flow.
    NRT.Rob
  • SWEI SWEI @ 2:34 PM
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    good point

    I'm used to modulating zone valves which we can use to enforce minimum flows.
  • Chris Chris @ 10:25 PM
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    Bumble Bee

    I'd more inclined to use a Delta-T pump over "P"
    In this case. Control delta you control flow rate. Can also
    do set point with it.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • FPEngineer FPEngineer @ 9:25 AM
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    Thanks for all the help!

    According to the TT manual, the flowrate through the heat exchanger needs to be a minimum of 5 GPM.  I have the internal Grundfos circulator set to LO. With 1 CH zone running I calculated the flowrate in the zone to be 1.4 GPM based on the delta T I measured across the zone and the heat load. I am struggling with figuring our a way to balance the flows in the zones to the flow in the boiler.  The flow in the zones is dependent on the # of zones running so this is a dynamic problem.  I notice a much longer delta T at the boiler when multiple zones are running. 

    Would it make sense to install a buffer tank on this system?  The zones and the boiler would draw from the tank so the flows would not have to balance.
  • Chris Chris @ 9:29 AM
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    Yes

    Of course it is..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • SWEI SWEI @ 10:45 AM
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    Bumble Bee

    I know it's a perfect fit for a boiler circ if he uses a buffer tank as a hydraulic separator.  Again, wish they offered more size options on the BumbleBee.

    Will the ∆T algorithm respond properly to zones turning on and off?  I can envision a few scenarios where it might mis-read the conditions.  ∆P will change flow based on zone valves and not fight the ORC.
  • Chris Chris @ 10:50 AM
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    SWEI

    I've had 2 Beta's running for 2 years piped along with Alphas so we could run each one at periodic times to compare. The Bee kicks its ***. Not only in its ability to move more GPM but less electrical usage as well. Yes it will react to the zones opening and closing.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Gordan Gordan @ 12:39 PM
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    How did you measure for the comparison?

    Did you go by what the circs were reporting, or did you have external measurements of some sort? I ask because, judging by the specs for both, the Alpha should have a slight edge in terms of max head and max flow, with little difference in power usage. It's always good to get these first hand reports, especially as the circ is not widely available yet. I like that it has a more granular GPM gauge, as long as it's accurate!
  • SWEI SWEI @ 1:07 PM
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    pump curves

    Are significant here, though the manufacturers don't go out of their way to mention it.  Running an ECM circ in the bottom 30% of its range most of the time will result in very low hydraulic efficiency.  No matter how efficient the motor is, if the pump can only transfer 30% of that energy into pressure, annual energy use will be higher.

    As soon as Taco offers some hydraulic options (003, 0010, etc.) for the BumbleBee, I'll start putting them on the majority of boilers.  Wilo offers a range of Stratos hydraulics, but nothing anywhere near as flat as a 0010 -- put the small one on a 399 and it never gets off the bottom of its curve.  That's ignoring completely the cost of actually making it work on ∆T (pump module, two sensors, and a controller.)  Same story for the Magna.
  • Gordan Gordan @ 1:31 PM
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    Can you elaborate?

    I'm not clear on how hydraulic efficiency relates to where on the curve you are, especially with ECM circs that vary their electrical consumption in order to meet lesser loads. Got any good links that explain this? Thanks in advance...
  • SWEI SWEI @ 2:02 PM
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    hydraulic efficiency

    Every pump has an efficiency curve as well as a pump curve.  They're not easily available for smaller circs, but if you look at something larger like http://www.taco-hvac.com/uploads/FileLibrary/KV,KS3007_1160.pdf you can see that there is a range near the middle of the hump in the curve where the pump works best.  Even with a VFD or an ECM, size matters!  Siggy covers this pretty well in MHH.
  • Gordan Gordan @ 7:48 PM
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    So...

    Looking at the alpha, the fixed speed 3 curve is concave and not convex (although the other two are slightly convex.) What would one conclude on the basis of that?

    I checked out what MHH had to say on the issue but there seems to be little in-depth discussion of variable speed ECM circs. I mean, hydraulic efficiency is what it is, but is it possible that with variable output wire-to-water efficiency could be good enough at lower outputs to make up for it?
  • SWEI SWEI @ 11:42 PM
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    curves

    Lowering speed with VFD generally shifts a pump curve towards the origin. The Alpha curves demonstrate that the relationship is a bit more complex than that, but starting in the sweet spot of the pump will improve things. A curve showing RPM versus hydraulic efficiency at differing system heads would likely prove interesting.
  • Chris Chris @ 3:37 PM
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    Based on Each

    Pumps own readings. They are hooked into a hydro air zone.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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