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tekmar control and slow response

carol_3
carol_3 Member Posts: 397
I'd try just a couple degrees of setback, and start the recovery a little earlier in the morning to see if you can get the temp you want. And since the wood floor is where you're having problem, set the other control for that mass

Comments

  • chelly
    chelly Member Posts: 3
    tekmar control and slow response

    We have in floor radiant heat with a tekmar 363 universal controller and 5 zones. I have a couple of questions. First, our heat is set at the thermostats to drop about 5 degrees at night, and come back up shortly before we get up. However, even several hours after we get up, the system still hasn't caught up. Is this normal? It seems like the system is set up to maintain heat, but isn't able to handle the ups and down of setting the heat lower at night, especially since the system has no way of knowing how cold the room is, only that there is a call for heat. I think part of the problem is that because I live in Fairbanks AK, where the coldest anticipated temperature is -40, the charactarized heat curve doesn't see +20 as very cold so the temp of the mix is pretty low (i.e. 85), which would explain why it would take hours to bring it up to 70.

    Second, the control asks for target values for the mix side, which I understand and the boiler side, which I don't understand. All zones occur after the mixing valve, so what does it mean when it is asking for terminal units, etc. on the boiler side? There are no terminal units on the boiler side.

    Finally, I have two zones downstairs,(garage and bedrooms) which are on a concrete slab, and three zones upstairs which are covered in hardwood, (two bedrooms and the LR, which is what we can't seem to keep warm enough). So should I choose high density or low density as my terminal unit, since I have some of each? Thanks for your help.


  • that's an extreme setback for mass radiant, and not a very good choice for any outdoor-reset-only system like yours. Outdoor reset is about tying your water temperature to your heating requirements. Setback requires the system to play "catch up". Since recovery takes so long, congratulations! That means your reset curve is very well adjusted. Stop trying to make it do setback and it should perform very well indeed. Or reduce your setback to just a degree or two.

    The 363 is also capable of doing outdoor reset for the boiler, and can handle a two temperature system. Since you only have a one temp system, it has capability you are not using. If it's never being asked to fire for a high temp (non-mixed demand) except DHW, those units should not be an issue. There are, I believe, still settings you need to set regarding boiler minimum temperatures and the like however. Read through the data brochure on the unit, it should tell you a lot about what it can do:

    http://tekmarcontrols.com/literature/acrobat/d363.pdf

    if you really, really have to have setback and don't want to sacrifice your reset, you could add a 369 zone controller and upgrade the thermostats to 062/063 RTU units and get indoor feedback as well, which will allow the system to intelligently raise the water temperature when it needs faster response, and lower it when it's "cruising". But personally I'd skip the setback and enjoy what I have.
  • carol_3
    carol_3 Member Posts: 397


    > that's an extreme setback for mass radiant, and

    > not a very good choice for any outdoor-reset-only

    > system like yours. Outdoor reset is about tying

    > your water temperature to your heating

    > requirements. Setback requires the system to

    > play "catch up". Since recovery takes so long,

    > congratulations! That means your reset curve is

    > very well adjusted. Stop trying to make it do

    > setback and it should perform very well indeed.

    > Or reduce your setback to just a degree or

    > two.

    >

    > The 363 is also capable of doing outdoor

    > reset for the boiler, and can handle a two

    > temperature system. Since you only have a one

    > temp system, it has capability you are not using.

    > If it's never being asked to fire for a high temp

    > (non-mixed demand) except DHW, those units should

    > not be an issue. There are, I believe, still

    > settings you need to set regarding boiler minimum

    > temperatures and the like however. Read through

    > the data brochure on the unit, it should tell you

    > a lot about what it can

    > do:

    >

    > http://tekmarcontrols.com/literature/acroba

    > t/d363.pdf

    >

    > if you really, really have to have

    > setback and don't want to sacrifice your reset,

    > you could add a 369 zone controller and upgrade

    > the thermostats to 062/063 RTU units and get

    > indoor feedback as well, which will allow the

    > system to intelligently raise the water

    > temperature when it needs faster response, and

    > lower it when it's "cruising". But personally

    > I'd skip the setback and enjoy what I have.



    I'd try just a couple degrees of setback, and start the recovery a little earlier in the morning to see if you can get the temp you want. And since the wood floor is where you're having problem, set the other control for that mass.
  • chelly
    chelly Member Posts: 3
    no setback?

    So the message we've heard all these years about saving energy by setting your thermostats back at night doesn't apply to these systems? Are they really that much more efficient that they save more energy than if you set the heat back?


  • setback on mass systems is much less effective, yes. they are generally speaking that much more efficient as well.
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