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How to check Dual Core RSS Transmitter Polarity

  • Updated

This article offers guidance on checking the CT Core polarity on the original Tigo Dual-Core RSS Transmitter. If you are seeking assistance for a newer series transmitter, the product descriptions and LED functions can be found at: RSS Transmitter with Pure Signal Technology

Contents: 

Overview


The Tigo TS4-F (Fire Safety) class units require a PLC (power line communication) signal to be constant, in order to pass voltage from the solar panel to the string. In most systems, this PLC signal comes from a Tigo RSS Transmitter or a UL PVRSS certified inverter (with internal Tigo Transmitter). The Tigo Dual Core RSS Transmitter can be deployed in 2 methods:

 

Independent Signal
(provides signal for separate string groups)

 Dual Core Reinforcement
(provides doubled signal on one string group)
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Whether a Dual-Core RSS Transmitter is deployed on 2 groups of strings (that are in close proximity), or doubled up on a single group, the CT Cores should be oriented in the same polarity or direction. If they are reversed, the RSS signal may be phased or canceled (even though the RSS Transmitter is on and the LEDs shows correct functionality).

Knowing if the polarity is correct, is an easy task with the newer CT Cores because they have been color coded, to make it easy to avoid confusion. However, the earlier versions of transmitters may include single-color (all black) Cores.

All Black Core Newer Color Coded Core
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For this reason, it may be necessary to know the correct methods for testing the polarity of the RSS cores, throughout the installation.

 

Testing Polarity

Although the RSS Transmitter is a DC device, it induces a PLC pulse or signal which is readable from an AC setting on a multimeter. This is important to know, for testing purposes.

 

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Tools Required:

  • A multimeter
  • A thin wire that can be bent, and is long enough to pass through both cores.
    12 - 16 gauge (4mm2 to 1.5mm2 ) is suggested, as it can pass through a home-run packed core, while still being large enough to take measurements. 

Instructions:

  1.  Disable Auto-Range on multimeter
    This function will not read properly, since the RSS signal repeats at 1-second intervals.

  2. Set multimeter range, anywhere from 100mA to 1A (AC).

  3. Confirm that the transmitter is on.
    There should be steady blue light (indicates transmitter has power) at the top left of the transmitter, and a blinking green light (indicates signal is being induced) between the two cores terminals, on the transmitter.

  4. Pass the testing wire through Core 1 (starting from the array side), then continue to pass the wire through the second Core (in the same direction).

    Direct through 2 separate groups Direct through 2 Cores on single group
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  5. Measure the ends of the test cable.  If a signal is present, there should be a pulse of 80mA (or more), at one second intervals.

If you do not receive confirmation (or are uncertain if a signal is present), perform a comparison by passings the testing wire through Core 1 (starting from the array side), and then passing the cable through Core 2 (starting from the inverter side), in a S-pattern:

Reverse through 2 separate groups Reverse through 2 Cores on single group
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Then, measure the ends of the test cable and compare the measurements:

    • If you have a pulse or signal above 80mA when the test wire is passed through both Cores, entering from the same side (from the array), then you have the correct polarity, and no further action is required.

    • If you have a pulse or signal above 80mA when the test wire is reversed (passed through Core 1, entering from the array side, and then passing through core two, entering from the inverter side), then your cores are in reverse polarity.  To correct, change the core's orientation (requires pulling the home run leads out), or swap the position of core 2's cables at the terminal on the RSS Transmitter.

 

Other Reasons for Canceled Signal

Wiring issues, design flaws, or lack of product knowledge can also contribute to reverse polarity or phasing scenarios which can disrupt, or cancel the signal. 

Common scenarios that can cancel transmitter signal: 

  • Loose or broken connector from RSS Transmitter to the Core(s)
    Make sure that connection to terminal is clean and always check for damage to the cables or CT Cores, incurred during installation, or during shipping/handling. 

  • String passing through or near, 2 different RSS Transmitter Signal cores
    Not as common, but definitely possible. Especially, if the installer is not aware that the inverter has an internal transmitter that is already providing a signal. If an external RSS Transmitter is installed without disarming the inverter signal, it could cause phasing or cancellation. 

  • Reverse polarity wiring in a parallel string design
    This is very common, as multiple home-run leads an jumpers can sometimes cause wiring confusion. The best approach is to test string polarity at the combiner.  

  • Cross-talk in cable tray or Conduit
    Cross-talk is a natural electro-magnetic occurrence that is caused by cable proximity. This is subject is often overlooked in system design.

  • Extreme string length or exceeding string-per-Core maximum
    The maximum string length for quality RSS Transmitter signal is 1000 ft / 305 m, and the maximum amount of strings per Core is 10. Designing above these parameters does not cancel or phase the signal, but it weakens the signal over the distance. For these, Tigo suggests using both Cores (of a Dual Core transmitter) on a single grouping of strings.  

 

For full system troubleshooting guidelines, download Tigo's TS4-F & RSS Transmitter Troubleshooting Guide.

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