[TRNSYS-users] Best Controller for Controlling Slab Surface Temperature?

[Ben Heymer]

Brad,

First make sure that the timestep you are using is small enough. You could
start with 1/120 hours, then increase while checking that the system
dynamics still make sense.

I recommend starting with a simple proportional controller (Type 1669 or
similar) which will simulate quickly and is quite typical for real-world
control of radiant slabs. If that doesn't track closely enough, you can try
the iterative controller (Type 22) which I find to be a good proxy for real
PID controllers (though it will slow down the simulation). There is a PID
controller in TRNSYS (Type 23) but that requires the simulation time step
to be similar to the real-world controller time step. This is not often the
case for HVAC simulations.

Ben Heymer, PE

On Sun, Sep 20, 2015 at 4:52 PM, Bradley Painting <paintingbr at appstate.edu>
wrote:

> I am attempting to control the surface temperature of a radiant slab by
> turning flow on and off through an active layer. The active layer receives
> a fluid of variable temperature. The allowable temperature range of the
> surface must be pretty small to achieve thermal comfort -- within a couple
> degrees.
>
> At first I tried using a simple Type2b differential controller, where the
> heating setpoint is the Upper Temperature and the slab surface temperature
> is the Lower Temperature. However, it doesn't seem like it is responding. I
> do anticipate a problem with this regardless because of the thermal lag of
> the concrete slab. Which controller within the TESS or standard TRNSYS
> library would work best? Thanks.
>
> --
>
> Brad Painting
>
> Master of Science Candidate, Renewable Energy Engineering
>
> Department of Technology & Environmental Design
>
> Appalachian State University
>
> Boone, NC  28608
>
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>
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