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Taco PC705, Has anyone used this? give details how.

eleft_4eleft_4 Posts: 509Member
Quoted from taco "PC705: VARIABLE SPEED PUMP INJECTION MIXING CONTROL

The Taco Mixing Control regulates the supply water temperature to a heating system by simultaneously controlling a boiler and the speed of an injection pump. Based on the outdoor air temperature, the PC705 continuously
adjusts the boiler differential to optimize the firing cycles of the boiler, prevent large water temperature swings, and increase the efficiency of the system. As the heating load increases, the Mixing Control speeds up the
injection circulator and as the load decreases it slows down the injection circulator. The Mixing Control features full diagnostics including a lighted bar graph that simulates the speed of the variable speed injection pump,
warm weather shut down, a maximum supply water temperature setting, and a boiler sensor that can be connected in order to prevent corrosion in the boiler due to flue gas condensation."





al

Comments

  • kevinkevin Posts: 420Member
    what more do you need?

    These are mfg. by tekmar for taco w/ imput from Sweet controls. I have used a bunch of the PC700s. very clean and the work right of a sr503/4/6 EXP relay. Very cool.They have a spiral bound book that is very detailed in wiring all their controls.Jim Simas @ Emerson Swan can give you some more info.kpc
  • eleft_4eleft_4 Posts: 509Member
    what more do you need?

    Thanks Kevin,


    I am looking to control the main loop circulator in place of a boiler by pass. I looked into Grundfos miximiser, it reads like the pump shuts off at 135* like an aquastat.
    This causes my variable speed injection to inject it's return water until the boiler temp comes up and the main loop circulator comes back on line. I have other zones taking off from the main loop. The main loop circulator needs to slow ,as the return water gets cooler, not stop so the boiler can catch-up.


    Kevin, define this statement quote from above. Is this the reverse of what I want?


    "As the heating load increases, the Mixing Control speeds up the injection circulator and as the load decreases it slows down the injection circulator."



    al
  • Jed_2Jed_2 Posts: 781Member
    What is your definition of \"the main loop circulator\"? NM

  • kevinkevin Posts: 420Member
    Al

    How familiar are you w/ injection loops? You probably know this.. It works off of a primary seconary loop. It involves three circs. 1 for the primary loop for the boiler. 1 for the radiant manifold loop, circulating from supply to return and 1 that injects hot water from the primary(boiler) loop to the radiant loop. This type of system is weather responsive and constantly adjusts to the outside temp.The radiant loop pump stays on most of the time. the injection pump adds more hot water to the radiant loop as the temp. drops outside, thereby mixing to a near perfect pecentage. You get less overshooting of temps and a much more steady even heating. Very nice and much better than using a 3way mixing valve. I hope this is helpful. KPC

    P.S. I am not so sure that this is what you want this control to do from your 2nd post. I believe it has boiler protection as a tekmar control would have but the main loop/ primary circ. is either on or off. I think the boiler protecton comes from shutting off the other zones from pulling hot water off the primary loop. That then allows the boiler to catch up by still running the burner and the primary loop pump only.The grundfos mixer is similar but I am not as familiar w/ it.
  • eleft_4eleft_4 Posts: 509Member
    Main loop

    Primary, wrong word "main"

    Jed, have you used this control?



    al
  • eleft_4eleft_4 Posts: 509Member
    Kevin

    kevin,

    As I understand it, the opus boiler uses this tech. to protect the boiler.

    I wonder if the sensor were put on the return if the control would see the load in reverse.

    return jpg; Zone valves with boiler bypass on left.


    al
  • kevinkevin Posts: 420Member
    i have seen ...

    this before..nice work.I knew you knew this.

    I thought that the sensor was suposed to go on the return side.so to protect from cold water shocking the boiler.
    Yes the opus and I think the Weil-Mcl GV use this same approach.
    I am not familiar w/ the Weil-Mc controls but i am sure they are pretty similar in a lot of aspects.
    I am most familiar w/ the Taco and like them because it is mostly plug and play. Kpc
  • eleft_4eleft_4 Posts: 509Member
    Sensors

    kevin,

    Looked up the specs, copied & pasted this:

    "Sensors 1 Outdoor Air & 1 Supply Water
    Power Supply 24 VAC (Powered by -EXP Relay)
    Variable Pump 240 V 50/60 Hz 2.4 A 1/6 hp"


    I didn't think this means return, that's why the question on reverse. Does this only work with a taco relay?

    al
  • Jed_2Jed_2 Posts: 781Member
    PC705

    I have sold may of these, and yes, they only work with the SR50x-EXP relay. or ZV40x-EXP. The have the plug in port required for coordination with the zone demands. It includes 1 outdoor sensor, 1 System Supply sensor, and 1 Boiler Supply sensor. By using the Mode switch set to Reset, the control protects the boiler from low Supply Temp. You can set this value.

    Hope this helps.

    Jed

    http://www.taco-hvac.com/current_category.41/prod_list.html?PHPSESSID=a23a859dbf10c3f21c3cfbfbb8c0775c
  • eleft_4eleft_4 Posts: 509Member
    PC705

    The specs read like it over rides the aquastat but not the high limit control in the aquastat. Do you remove the aquastat and install a high limit control in it's place?


    al
  • Jed_2Jed_2 Posts: 781Member
    PC705

    This control is not as sophisticated as the 362. The 362 allows direct control of the boiler(Term.6&7, Blr). The 705, when in Reset Mode, as I read it, controls boiler operation through the Relay End Switch, and varying the speed of the injection pump, to control boiler Supply Temp. It continually adjusts boiler differential, I think, through the speed of the injection pump(mixing load), not the Primary pump. High temp zones would funcion normally, through the zone relay. this doesn't answer all your questions, but hope it helps. I don't believe you can use it to control the Primary Pump, as you suggest. I could be wrong. Interesting idea, though.

    Jed
  • eleft_4eleft_4 Posts: 509Member
    705 vs 356

    Jed,

    Check out tekmar's (E 021) Fig 11 in the 356 control on their web site. It looks close to what I should do without re piping.

    al
  • Jed_2Jed_2 Posts: 781Member
    362

    Eleft, I believe you'll need a floating action control to modulate the valve motor. Don't think the 356 can do this.

    Jed
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