Re: [TRNSYS-users] Type4 - control strategy

[Jeff Thornton <thornton@tess-inc.com>]

> I would like to use Type4 storage tank with one auxiliary heater, only controlled by a ON/OFF controller (Type2). 
> However, it seems that the other conditions (temperature conditions inside the tank: Tthermostat < Tset and Tnode < Tset - Tdb) already control the ON/OFF cycle of the auxiliary heater. 
> What can I do to avoid those two conditions ? If I give the same value to Tdb and Tset , auxiliary heater doesn't work.
> I modeled a tank with one node.

Set the capacity of one of your heaters to zero.  Set the capacity of the other tank heater to the capacity of the real heater.  Set the deadband to zero and the temperature setpoint to 100000.  Connect the temperature of the tank to Type 2 and then pass the output signal from Type 2 back to the storage tank as the input control signal for the heater.  That's it.  By setting the thermostat to a large temperature you are insuring that the element can't meet the setpoint when it is activated.  Two things to remember.  1) You'll need a small timestep if you use Type 2 coupled to the tank - that's why the tank has its own control algorithm built in.  2)  Make sure you connect the output of Type 2 to the input of Type 2 so you use the hysteresis function inside Type 2.

Jeff

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Jeff W. Thornton
President - Thermal Energy System Specialists
2916 Marketplace Drive - Suite 104
Madison WI 53719
(608) 274-2577