Emerson E2 Dual Temp Control, Light Control, Clean/Wash Mode, Dewpoint Input Sources

Full OFF setpoint). Based on this comparison, the anti- sweat heaters will do one of three things:

•If the input is equal to or above the Full ON set- point, the heaters remain ON 100% of the time.

•If the input value is equal to or below the Full OFF setpoint, the heaters will be ON 0% of the time (fully OFF).

•If the input value is between the Full ON and Full OFF setpoint, 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 how anti-sweat con- trol works. The setpoints (Full ON dewpoint= 80°F, Full OFF dewpoint = 20°F) form the range of dewpoints across which the heaters will be pulsed. When the measured dew- point is 45°F (directly in between both setpoints), the per- centage will be 50%, and the heaters will be pulsed ON for 5 seconds of the defined 10-second interval. If the dew- point drops to 30°F, the percentage will lower to 20%, and the heaters will be on only 2 seconds out of every 10.

Figure 11-6- Illustration of Anti-Sweat Control

11.4.5.1Dewpoint Input Sources

Dewpoint control inputs for the case controller’s Anti- Sweat algorithms must come from a dewpoint probe set up on the E2 I/O Network.

Note that when using a dewpoint probe on the E2 I/O Network, the case controller will rely on the E2 to provide the anti-sweat control value. If communications with the E2 are lost, the case controller will enter Fail-Safe Mode (see Section 11.4.11) and default to a fixed 50% output.

11.4.6 Dual Temp Control

A case controller can be configured to change its case temperature, alarm, and superheat setpoints when an exter- nal digital input is switched ON or OFF.

The user simply connects the digital switch to an input point on the RS485 I/O Network and configures the case controller to read that input as a dual temp switch. When the dual temp switch is ON, the case controller overrides its normal case temperature, alarm, and superheat set- points with a set of user-specified alternate setpoints.

11.4.7 Fan Control

A relay on the power module activates the case fans. The fans will be ON while in refrigeration mode, and they may be programmed to be either ON or OFF when the temperature setpoint is satisfied and refrigerant is not flowing.

When in defrost mode, the fans default to OFF, but they may be programmed by the user to be either ON or OFF.

When a liquid-side CCB is in Recovery Mode (see Recovery Mode, page 9-10), Fan Control may be config- ured to delay the activation of fans for a user-specified amount of time. This delay helps keep the fans from splashing excess moisture that may still be on the coil.

11.4.8 Light Control

Lights are activated and deactivated by a relay on the power module.

The case controller itself does not have any special control algorithm for the case lights other than to leave the lights ON during normal operation. There are only two cases where the lights are not always ON:

1.An override from an E2 takes over control of the case lights. This override may take the form of a manual switch or a schedule output.

2.If the case controller is set up to use Walk-In Box Control, the case lights default to OFF and only come ON when the door switch is tripped. See Section 11.4.10, Walk-In Freezer Control.

11.4.9 Clean/Wash Mode

Clean Mode is a special kind of case deactivation designed specifically for washing or performing mainte- nance on the case.

Clean Mode is initiated by activation of a cleaning switch input or by a command sent from a Hand-held Ter- minal or an E2. During Clean Mode, refrigerant flow is turned OFF, all fans and anti-sweat heaters are deacti- vated, and the lights are turned either ON or OFF as pro- grammed by the user.

11-14 • E2 RX/BX/CX I&O Manual 026-1610 Rev 13 14-SEP-2011