Emerson E2 Anti-Sweat Setup, Heat/Cool Control, How Anti-Sweat Works, Unoccupied Hysteresis

11.16 Anti-Sweat Setup

An anti-sweat application controls one anti-sweat zone. An anti-sweat zone is defined as one or more anti- sweat heaters that use the same dewpoint (or RH and tem- perature) sensors and the same control setpoints. If all the outputs on a 20-channel PMAC panel are going to use the same setpoints and dewpoint device(s), then all the heaters may be set up in a single zone.

Zones are set up in a single screen called the Anti- Sweat Control Setup screen.

11.16.1 How Anti-Sweat Works

Anti-sweat applications control anti-sweat heaters by monitoring the dewpoint. A dewpoint value may come from a dewpoint probe mounted within the Zone, or it may be calculated automatically by the E2 using a combination of a relative humidity sensor and a temperature sensor.

The dewpoint value is used to pulse the heaters ON for a certain percentage of a user-defined time interval. The dewpoint is compared to the anti-sweat application’s con- trol setpoints (the Full ON Dewpoint and the Full OFF Dewpoint). Based on this comparison, the anti-sweat heat-

its relation to the heating or cooling setpoint. Both staged and modulated (0-100%) heating and cooling outputs are supported by Heat/Cool Control.

Heat/Cool controls are available in RX units, allowing small installations with simple HVAC systems to use one controller for all refrigeration and HVAC systems.

11.17.1 Temperature Control

Heat/Cool applications use PID control to vary the out- put of heating and cooling devices. As is the case with all applications that use PID control, Heat/Cool control makes use of a PID setpoint and a throttling range. Refer to Appendix D: PID Control for more information.

Unlike normal PID loops that assume a 50% output is required to keep the temperature stabilized on the setpoint, Heat/Cools strive to stabilize the temperature on the set- point with the output at 0%. Thus, when the temperature goes below a heating setpoint or above a cooling setpoint, the heating or cooling outputs climb from 0% to 100% as determined by the throttling range (see Figure 11-25).

Lighting Control Command Cells

ers will do one of three things:

•	If the dewpoint is equal to or above the Full ON
	Dewpoint, the heaters remain ON 100% of the time.
•	If the dewpoint is equal to or below the Full OFF
	Dewpoint, the heaters will be ON 0% of the time
	(fully OFF).
•	If the dewpoint is between the Full ON and Full

Input Value	DVCOMBINER
1 - 4	In 1	Out
DV	In 2
	In 3
	In 4
Alt Combiner	Use Alt Comb
DV
	Comb Type
	Alt Comb
	Invert Output

	SCHEDIF
	Logic In
Occupied	Sched In
DV		Out
Alt Schedule
	Use Alt Sch
DV
	Comb Type
	Alt Comb
	Invert Output

OFF Dewpoint, the heaters will be pulsed ON for a

percentage of the specified time interval. The per-

centage is determined by proportionately measuring

where the dewpoint falls between the range of val-

ues formed by the two setpoints.

Figure 11-6shows an example of an anti-sweat appli- cation. The setpoints (Full ON = 80°F, Full OFF = 20°F) form the range of dewpoints across which the heaters will be pulsed. When the measured dewpoint is 45°F (directly in between both setpoints), the percentage will be 50%, and the heaters will be pulsed ON for five seconds of the defined 10-second interval. If the dewpoint drops to 30°F, the percentage will lower to 20%, and the heaters will be on only two seconds out of every 10.

11.17 Heat/Cool Control

Heat/Cool Control is a special kind of sensor control that applies to heating and cooling devices. Heat/Cool Control applications use PID control to vary the amount of heating and cooling based on the current temperature and

MIN ON/OFF		ONESHOT
			OVERRIDE
In	Out	Trigger Out	In	Out
			Command	LIGHTS
Min On/Off Times			(on, off, normal)
Min On/Off Delays			Type
		Pulse Width	(timed, fixed)
		Timer	OV time

26512043

Figure 11-25- Example of Heat/Cool PID Control

By default, only the proportional and integral modes of PID control are enabled for Heat/Cools. The user may choose to add the Derivative mode or to get rid of the Inte- gral mode and use strictly Proportional control.

11.17.2 Unoccupied Hysteresis

When the Heat/Cool receives an indication that the building is unoccupied, the control mode changes from the PID method described previously, and uses simple ON/ OFF control of the heating and cooling outputs.

The Heat/Cool application in unoccupied mode makes use of a hysteresis value to form a range of temperature values across which the heating and/or cooling will be applied. As shown in Figure 11-26, when the temperature

Anti-Sweat Setup Software Overview • 11-45