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WARNING: This article is for qualified professional electrical installers only. System owners (consumers) must not follow these instructions. Incorrect installation or handling of electrical equipment can cause serious injury, fire or damage to your system, and you may lose your warranty. If you are a system owner and need help, contact your Emaldo® installer directly. |
This article explains how to set the CT ratio on the ADL400 smart meter that is connected to CT clamps. A CT clamp (current transformer clamp) measures the current in a cable. The article is for professional installers.
You must set the CT ratio to match the installed CT clamps before you use the meter. If the ratio is wrong, all current, power and energy readings will be wrong by the same factor.
This guide applies to the CT-connected ADL400. You can use the same method to change the other settings of the meter.
Before you start
Safety: A qualified electrician must carry out the installation. Never leave the secondary leads of a 5 A CT open while the clamp is around a live conductor. Connect the CT leads to the meter before you close the clamp around the conductor. Disconnect the leads only after you have removed the clamp.
Compatible CT clamps: The meter only works with CT clamps that have a 5 A secondary output (marked “/5A”). CTs with a mA or 333 mV output are not compatible.
For general installation and wiring of the smart meter, see How do I install the meter correctly for the Emaldo® Power Core, Store or Sense?
Calculating the CT ratio
The value to enter is the primary current of the CT divided by its secondary current (5 A). The primary current is the first number in the CT rating, before the “/”.
| CT clamp rating | Calculation | Value to enter |
|---|---|---|
| 150/5 A | 150 ÷ 5 | 0030 |
| 200/5 A | 200 ÷ 5 | 0040 |
| 250/5 A | 250 ÷ 5 | 0050 |
For other CT clamps, use the same calculation.
The meter buttons
The three buttons below the display are used to view readings and to change settings:
| Button | Image | Normal use | In the setup menu |
|---|---|---|---|
| UP (Voltage/Current) | Shows voltage and current | Moves the cursor to the next digit | |
| DOWN (Power) | Shows power | Changes the flashing digit | |
| ENTER (Energy) | Shows energy | Opens and closes the menu, and confirms |
Setting the CT ratio
- Press and hold ENTER until PASS is shown, then press ENTER. The display shows 0000.
- Enter the password (default: 0001). Use UP to move the cursor and DOWN to change the digit, then press ENTER. If the password is wrong, the meter shows FAIL and returns to the normal display.
- Use UP or DOWN to scroll through the settings until Ct is shown on the top line. Press ENTER. A digit starts to flash.
- Enter the CT ratio for your CT clamps (see the table in “Calculating the CT ratio”). Use UP to move the cursor and DOWN to change the digit. Press ENTER to confirm. The digits stop flashing.
- Press and hold ENTER until SAVE is shown. Use UP or DOWN to select YES, then press ENTER to save. To exit without saving, select NO and press ENTER.
Prefer to watch? See the step-by-step video on setting the CT ratio.
Installing the CT clamps correctly
Correct selection and installation of the CT clamps is essential for accurate measurements and correct system operation.
Location: Install the CT clamps at the grid connection point, after the utility meter and before any loads or other connections. This way the meter measures the total import and export of the whole installation. Do not install the clamps on sub-circuits.
Direction: The arrow on each clamp must point towards the load (away from the grid). Connect the S1 and S2 leads of the CT to the correct current input terminals on the meter. See the CT-meter wiring diagram and the CT clamp direction illustration in the meter installation article. If one CT is reversed, the meter measures that phase backwards. This makes the total import, export and power readings incorrect.
Phase matching: Connect each CT clamp to the meter input for the same phase that it is clamped around (L1 to L1, L2 to L2, L3 to L3). The meter combines the current of each phase with the voltage of that phase. A mismatch gives incorrect or negative power readings. The phases on the smart meter must also match the phases on the Emaldo® Grid Connector. For details, see the meter installation article.
Rating: Choose a CT rating that is equal to or higher than the maximum current of the installation, for example the main fuse rating. A CT that is too small may give incorrect readings under high load. A CT that is much too large reduces accuracy at low loads. The clamp opening must also be large enough for the cable.
Mounting: Clamp each CT around a single conductor only. Never clamp it around a multi-core cable, or around both a phase and a neutral conductor. The currents cancel each other out and the reading will be close to zero. Make sure the clamp is fully closed with no gap.
Further help
- How do I install the meter correctly for the Emaldo® Power Core, Store or Sense?: wiring diagrams, CT direction, communication cable and phase matching.
- Installation video – Installing the CT meter (from 4:06)