Component 406:  High Limit or Low Limit Controller by HVACSIM+

General Description
	This component represents a proportional controller which exerts a 
control action only when the measured input signal is on one side of a fixed 
setpoint.  For a high limit controller, no control action is exerted unless the
measured input signal exceeds the setpoint.  For a low limit controller, 
control action is exerted only when the controlled input falls below the 
setpoint.  The setpoint is determined by the absolute value of the second 
parameter.  The component represents a high limit controller when the second 
parameter is positive, and a low limit controller when the second parameter is
negative.  The measured input signal, generally representing a temperature, 
must be a control variable between zero and one, which can be obtained by 
passing a temperature through the Component 409 temperature sensor model. The 
setpoint parameter must also be a normalized control variable with an absolute
value between zero and one.

Nomenclature
	C - output control signal (0 <= C <= 1)
	CTm - measured temperature input control signal (0 <= CTm <= 1)
	CTs - temperature setpoint parameter (0 <= |CTs| <= 1)
	Kp - proportional gain

Mathematical Description
	E = |CTs| - CTm
High limit controller (CTs >= 0):
	If (CTm > CTs)	C = C + Kp*E
Low limit controller (CTs < 0):
	If (CTm < |CTs|)	C = C + Kp*E

Component 406 Configuration
	Inputs		Description
	1	CTm	- measured temperature input control signal
	2	C	- controller output
	Outputs		Description
	1	C	- controller output
	Parameters	Description
	1	Kp	- proportional gain
	2	CTs	- setpoint times i, where i = -1 for low limit
			  controller, or i = 1 for high limit controller

Reference:
1.	HVACSIM+ Building Systems and Equipment Simulation Program Reference 
	Manual (NBSIR 84-2996)
	Daniel R. Clark
	United States Department of Commerce
	National Institute of Standards and Technology
	Gaithersburg, Maryland  20899-0001