[TRNSYS-users] Type2d Controller / Type108 + Setpoints

[David BRADLEY]

Michael,
   What you are seeing isn't wrong; it is how actual HVAC systems work. 
Thermostats have a deadband. They don't turn on heating until the room 
temperature drops slightly below the set point and they keep heating 
until the room temperature is slightly above the set point. Usually the 
deadband is 1 or 2C.

   I think that what you are running into is difficulty in changing 
setpoints, not in anything that has to do with hysteresis. Type108's set 
points are inputs so you can set them to 21 during the day and 18 at 
night. You can define a Type14 that sets the set point as a function of 
time or you can use Type514 from the TESS Applications library.
Best,
  David


On 11/22/2012 06:43, Michael Diekerhof wrote:
> Dear all,
>
> I´m using Type 2d to turn on my heat pump (type401) in case of the 
> roomtemperatur falls below 18°C and to turn it off, if Troom is >21°C.
>
> My basic parameters are:
>
> Upper input value = 0
> Lower input value = Troom
> Upper dead band = -18
> Lower dead band = -21
>
> This works fine but the problem is just that Troom always fluctuates 
> between 21 and 18 like a sawtooth function. The same result appears if 
> i use type108. Of course this is a result of the hysterese but i would 
> like to keep the roomtemperature on a certain level depending on the 
> daytime.
>
> But how can i adjust that the set roomtemperature should be 20°C 
> during the day and 18°C at night ??????
>
> As i worked with type23 (PID Controller) I used type 14 and an 
> equation to give a setpoint to type23. *But how can i give a setpoint 
> to type2d or type108 since there´s no input variable for that ?
> *
> **
> **I would appreciate any kind of help
>
> best,
>
> Michael
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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