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Tekmar 150 Setpoint Help .. Please

MikeL_2 Member Posts: 459
The designer of the system is using one Tekmar 150 to control the temp of the garage slab and one to control the staple up (instead of air thermostats). There is a fan coil in conjunction with the staple up that is controlled by a conventional thermostat.




  • MikeL_2
    MikeL_2 Member Posts: 459
    Tekmar 150 Set Point question

    Does anyone have opinions on initial settings for a Tekmar 150 Set point controller for a in slab plus staple up job?

    The in slab is in a well insulated garage (cold climate -30F design temp.)

    The staple up is the rest of the house with heat transmission pans and foil bubble insulation.

    Mixing is controlled by a Tekmar 356 hooked to a NTI Trinity 200 boiler.

    My installer did not have much knowledge of the set point controls. He suggested for the 150: pulse mode, differential of 4 Deg F, cycle length of 4 minutes for both slab and staple up.

    The garage slab sensor seems to be making heat
    demands quite quickly and for short periods.

    The Tekmar data brochure says longer cycle lengths for slabs, shorter for quicker response systems. But how long should I make the slab cycle and the staple up cycle?

    Any help with better settings would be appreciated.

  • Josh M.
    Josh M. Member Posts: 360

    Dan, I can't figure out for the life of me what the 150 is doing. You have a 356 that should be controlling ALL of your logic for a system like that. Can you give us a better description?
  • Josh M.
    Josh M. Member Posts: 360

    Dan, I hate to say it but the 150 isn't really designed to be a thermostat. With the 356 controlling your heating curves you should never have a differential setting. Meaning don't have any delays programed in or temperature differentials.

    I would set them for a constant setpoint with no differential and leave em be.
  • ALH_4
    ALH_4 Member Posts: 1,790

    My understanding is that the hysteresis of the thermostat/setpoint control requires some kind of differential. You can't turn the heat on and off at the same temperature or it will be switching all the time.

    I'm still not sure I understand what your installer was trying to do. The 150(s) are unnecessary unless a constant floor temperature is your goal. Normally you would control the floor temperature in the house with the boiler control and the floor temperature in the garage with the 356.

    Do you run the garage all the time? Is it a work space? I assume the 356 is providing a set fluid temperature to the garage floor and is not on outdoor reset.

    Are the heat transmission pans the sheet metal type omega-plates? Is the tube pex or EPDM rubber? Is your boiler running on outdoor reset? Is the reset curve set correctly?

    Based on what I know, I really don't think you need the 150 control at all.
  • Josh M.
    Josh M. Member Posts: 360

    However with outdoor reset control you want to keep the heat on all of the time. Mabe a 1 degree differential which is the lowest setting for the 150. Load-matching, that is the idea of outdoor reset. If you have the correct water supply temperature you shouldn't even need a thermostat. I like to think of the thermostat as a high limit control.

    Proportional heat supply. Siggy had a good article this month in P&M about the subject.
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