Nova Controller On/Off Control Capabilities

The PD540 series Nova Digital Controller are capable of both PID and simple On/OFF control. When On/Off control is enabled, all PID based parameters and groups, such as G.PID and G.AT are disabled. During On/Off control, the Output 1 relay is locked into a control function. Sub1 and Sub2 relays (options) can be set for On/Off control or as alarms. The analog outputs maintain their normal setup options, however the control output levels will only function at 0 or 100 percent of full scale.

How to Activate On/Off Control

To engage On/Off control, the OnOf parameter must be turned on. Press and hold the SET/ENT button for three seconds to enter the setup groups. Use the up and down arrow keys to select the control group (G.CTL), and press SET/ENT. Continue to cycle through the control group parameters to locate the parameter OnOf. This is the parameter to enable On/Off control. Set as desired, and press and hold the SET/ENT key for three seconds to return to the main operating display.

On/Off Control Functionality

When in On/Off control mode, the relays and analog outputs operate differently then when operating as PID controlled time proportional relay, 4-20 mA, or 15 VDC voltage pulse modes. The relay control outputs will be energized when "on." The analog outputs will either be "on" (4-20 mA or 15VDC constant) or "off" (4mA or 0VDC constant).

On/Off behavior is based on the hysteresis settings established in the output parameter group (G.OUT). The parameters used and operation behavior is shown below.

This parameter sets hysteresis in case of On/Off control output mode in a H/C model.
This parameter sets the hysteresis high limit for on/off relay control mode in normalmodels (non-Heating/Cooling models).
This parameter sets the hysteresis low limit for on/off relay control mode in normal models(non-Heating/Cooling models).

On/Off condition is based on the Hysteresis settings, determining the On/Off conditions based a deviation from the SP.
Note: In H/C models, HYS.H and HYS.L are replaced by HYS, and range high and low is ½ the HYS setting.

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