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TT Prestige Solo60 trimax control logic

smp74
smp74 Member Posts: 61
After much consideration of different systems I decided to go with a TT Prestige Solo60 and a Smart40 for DHW.

After watching it run, I think there is a problem somewhere and I'd like to ask for some input on what we should be looking at.

The situation is this:
When the heating zone calls, boiler starts out at low fire and after about 5 or so minutes the temp on the reset curve is satisfied (120F currently). Then the burner starts rapidly cycling on low fire on 30 seconds, off 15 seconds, on 30 seconds, off 15 seconds. Output temp varies 120 - 122 during this rapid cycling. The thing that doesn't make sense is that the "CH Call Blocking" feature is set to 5 minutes to avoid this, yet the burner is still cycling like crazy.

I called up Triangle Tube about this and they confirmed that the "CH Call Blocking" feature should stop the burner from firing again until the time has elapsed, regardless of whatever the supply temp has fallen to.

So, is there any insight as to where to look for the cause of the rapid cycling and ignoring of the "CH Call Blocking" setting?

Cheers.


Comments

  • smp74
    smp74 Member Posts: 61
    Adding another observation:

    It appears that it is not reaching setpoint even at 120F. The control constantly displays "CH Demand". Output temp is 120, return 118, burner fires at 49% for about 5 seconds and immediately ramps right down to 1% then shuts off when output temp is 124 and input is 120. Output drops to 120 again, burner fires and shuts off quickly as above, repeat. I sat down and watched this cycle go on and on about 100 times. "CH Setpoint Reached" was never displayed, always in "CH Demand" the whole time. I assume this is why the CH Call Blocking function is not having any effect since setpoint is never reached. Question is why.
  • unclejohn
    unclejohn Member Posts: 1,749
    Normally this is due to having to small a load operating. Say a small bedroom with 8' of baseboard. The boiler can't turn down that low. You need a buffer tank. Or you have a valve shut somewhere.
  • smp74
    smp74 Member Posts: 61
    The load in question is 45ft (actual emitter) of high output fin tube baseboard. All valves are open.

  • Aaron_in_Maine
    Aaron_in_Maine Member Posts: 315
    edited July 2015
    I think the blocking means if the thermostat is satisfied and another one calls the boiler won't fire unit the timer runs out. Your watching one call for heat. A buffer tank would help for small loads.
    Aaron Hamilton Heating
    [email protected] yahoo.com
    (207)229-7717
  • smp74
    smp74 Member Posts: 61
    Is 45ft of high output fin tube considered a small load?

    TT confirms that the call blocking feature is supposed to function *during a heat call to stop the burner from doing exactly what it is doing now. They also said that there is a 6F differential for the boiler to be satisfied on a heat call.

    I watched some more and the burner is shutting off several times before it even gets to the 120F. Burner fires, runs a minute or two then shuts off at 116. Runs again, shuts off at 118. etc.

    Also, the deltaT on the heat exchanger only ever reaches 4F max. I'm wondering if the boiler circulator is flowing too much and not allowing the boiler to see any temp drop across the heat exchanger. It is pumped p/s and the boiler loop is 1" copper with a Taco 0010, total pipe length is about 4ft. According to the TT manual, a Taco 005 would provide way more than the minimum flow requirement of 3gpm for max fire.

    If I leave the thermostat calling for heat and shut off the ball valve on the baseboard zone, the boiler will go up to 126 and then display "CH Setpoint Reached". At this time if I open the valve again, temp will drop below 120 and the call blocking time takes effect and burner will not fire again until the time has elapsed. (thermostat is calling the whole time)
  • smp74
    smp74 Member Posts: 61
    Update: More info from TT tech support.
    They confirm that the 0010 is WAY too big for the solo60. Max fire only requires about 4GPM. They recommend to install smaller 3 speed circ on low or medium speed.
  • Zman
    Zman Member Posts: 6,990
    That should solve it. When you over pump a mod con that much, it can't read a difference between the supply and return temp. This confuses the controller.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • smp74
    smp74 Member Posts: 61
    Yep, that does indeed look like the case here. Tech came to house this morning and confirmed. Boiler circ will be changed out next week sometime. Will post back with results.
  • smp74
    smp74 Member Posts: 61
    Boiler circulator changed to BumbleBee set on low speed. Running better now and getting some delta on the heat exchanger. It seems that with the low resistance of the fire tube design that it's key to have a small enough circulator. Power consumption also dropped a lot compared to the 0010 that was in there before.

    (note: disappointed with the installer overall, should have went with Garrity. Lesson learned.)
  • JStar
    JStar Member Posts: 2,752
    Somebody ought to put the recommended circulator sizes in the manual somewhere. Oh, wait...
  • smp74
    smp74 Member Posts: 61
    Yep, exactly. I pointed that out to them for sure.

    We'll see how it runs during heating season.
  • JStar
    JStar Member Posts: 2,752
    With a shedding load in the circuit, the delta-t should increase a bit. The BumbleBee can be set up to modulate on temp. difference as well, which would ensure a nice, smooth operation.
  • SWEI
    SWEI Member Posts: 7,356
    JStar said:

    Somebody ought to put the recommended circulator sizes in the manual somewhere.

    They do, but 90% of them are still too big.
  • smp74
    smp74 Member Posts: 61
    SWEI said:

    JStar said:

    Somebody ought to put the recommended circulator sizes in the manual somewhere.

    They do, but 90% of them are still too big.