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First Winter with TT Solo 110

FPEngineerFPEngineer Member Posts: 25
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.


  • ChrisChris Member Posts: 3,056
    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."
  • Paul48Paul48 Member Posts: 4,257

    a problem........If you want to zone that boiler with circulators, it has to be piped P/S. Yours isn't piped P/S.
  • ZmanZman Member Posts: 3,517

    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.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • FPEngineerFPEngineer Member Posts: 25
    edited November 2012
    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.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • ChrisChris Member Posts: 3,056
    edited November 2012
    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."
  • clammyclammy Member Posts: 1,996
    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 .
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • GordanGordan Member Posts: 891
    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.
  • FPEngineerFPEngineer Member Posts: 25
    edited November 2012
    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.
  • ChrisChris Member Posts: 3,056
    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."
  • FPEngineerFPEngineer Member Posts: 25

    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.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • GordanGordan Member Posts: 891
    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. :-)
  • JasonJason Member Posts: 294

    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.
  • GordanGordan Member Posts: 891
    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.
  • ChrisChris Member Posts: 3,056
    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."
  • FPEngineerFPEngineer Member Posts: 25
    Outdoor Reset

    Yes, I am using the outdoor reset.
  • Paul48Paul48 Member Posts: 4,257
    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.
  • FPEngineerFPEngineer Member Posts: 25

    Can I use the valves on the return to throttle down the flow on the zones?
  • GordanGordan Member Posts: 891
    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?
  • Paul48Paul48 Member Posts: 4,257

    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.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • Paul48Paul48 Member Posts: 4,257

    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.
  • GordanGordan Member Posts: 891
    edited November 2012
    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.
  • ChrisChris Member Posts: 3,056
    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."
  • FPEngineerFPEngineer Member Posts: 25
    edited November 2012
    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.
  • ChrisChris Member Posts: 3,056
    edited November 2012

    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."
  • SWEISWEI Member Posts: 7,356
    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.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • SWEISWEI Member Posts: 7,356
    boiler differential

    Are you measuring on high fire at full load?
  • FPEngineerFPEngineer Member Posts: 25

    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.
  • GordanGordan Member Posts: 891
    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.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • SWEISWEI Member Posts: 7,356
    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. 
  • GordanGordan Member Posts: 891
    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?
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • FPEngineerFPEngineer Member Posts: 25
    More pictures

    Pictures of the TT Solo 110 without the cover and a closer pic of the internal circulator.
  • FPEngineerFPEngineer Member Posts: 25
    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.
  • GordanGordan Member Posts: 891
    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.
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