Option PT improves support for potential transformers (PTs), making it easier to use WattNode® for LonWorks® meters with medium voltage services. Specifically, Option PT adds a configuration property UCPTptRatio which configures the ratio of the external PT, allowing the meter to automatically scale the voltage, power, and energy readings.

Continental Control Systems (CCS) offers Option PT for the WattNode for LonWorks, Plus and Logger models. Option PT is not available with Option B or Option BI. It is still possible to use potential transformers with WattNode models that do not explicitly support PTs, but you must scale the same variables by the PT ratio to get the correct values.

Ordering

Any WattNode for LonWorks (Plus or Logger) (but not Option B or BI models), may be ordered with Option PT by adding one of the following options to the model number.

Opt PT

This ensures that the WattNode model includes the special PT firmware version. The PT ratio will default to 1.0, which is the same as not using a PT. It will be necessary to set the PT ratio in the field using the UCPTptRatio configuration property. For example: WNC-3Y-208-FT10 Opt PT

Opt PT=nn

This ensures that the WattNode model includes the special PT firmware version, and factory configures the PT ratio to nn. The PT ratio may be any value between 0.05 and 300. It is still possible to change the PT ratio in the field using the UCPTptRatio configuration property. For example: WNC-3Y-208-FT10 Opt PT=60

Common PT Ratios

PT Primary Voltage PT Secondary Voltage
(Line-to-Neutral)
Ratio = UCPTptRatio
840 120 840:120 = 7
1200 120 1200:120 = 10
2400 120 2400:120 = 20
4200 120 4200:120 = 35
4800 120 4800:120 = 40
7200 120 7200:120 = 60
8400 120 8400:120 = 70
12000 120 12000:120 = 100
14400 120 14400:120 = 120

Manual Supplement

Updates

To fully take advantage of Option PT with LNS® based systems, you may want to use the following:

See Also