In myenergi installations, Current Transformers (CTs) are vital for monitoring electrical currents at key points, such as the grid connection, solar or wind inverter, or a static battery system. Among these, the installation of a Grid CT sensor is imperative for safety and system efficiency. Fitting the Grid CT is not optional—it is essential for enabling the ECO modes and ensuring the overall safety and functionality of the system.
Importance of the Grid CT for Safety
The Grid CT sensor must be installed at the grid connection point. This ensures that the system accurately monitors the flow of electricity, both imported and exported, and prevents dangerous overloads that could trip the supply or cause a fuse to blow. Without the Grid CT, critical safety features like load balancing and Grid Limit settings cannot function correctly, which could result in serious electrical hazards.
For maximum safety, the Grid CT must be connected to the master device in the system, which typically manages the overall energy distribution and monitoring. This positioning ensures that the sensor captures accurate readings and allows the myenergi system to operate safely and efficiently.
Guidelines for Installing the Grid CT Sensor
The Grid CT sensor, provided with myenergi devices, needs to be correctly installed around either the Live or Neutral meter tail of the electricity supply meter. The correct placement and orientation of this sensor are crucial for ensuring accurate monitoring and maintaining safety:
- Device Compatibility: The Grid CT sensor can be connected to any myenergi device with a CT input, such as the eddi or zappi (for wired sensors) or the harvi (for wireless sensors).
- Positioning: The sensor must be installed upstream of any junction box or Henley Block, ideally within the consumer unit, to ensure that it monitors all imported and exported power.
- One CT per Phase: Only one Grid CT should be installed per phase in the entire installation. Additional CTs can be used for other purposes, but there should only be one at the grid connection point to avoid conflicts and ensure accurate monitoring.
- Cable Selection: The CT sensor should be installed on either the Live or Neutral cable. If placed on the Live cable, the arrow on the sensor must point towards the consumer unit (indicating the direction of grid import). If on the Neutral cable, the arrow should be reversed.
- Secure Fitting: The CT sensor must be fully closed and securely clicked shut to ensure it functions properly.
- Wiring: Ensure the CT sensor is wired correctly, with the black wire connected to the negative terminal (–) and the red wire to the positive terminal (+). Incorrect wiring can lead to swapped import and export readings, potentially compromising the safety of the system.
CTs and Load Balancing for Safe Operation
Beyond safety, CTs are also crucial for managing the current drawn by myenergi devices, preventing circuit overloads through load balancing or load curtailment. By setting a Grid Limit, users can define the maximum current that can be drawn from the grid connection, ensuring that devices like the zappi adjust their current draw to avoid exceeding this limit.
For example, in a property with a grid supply limit of 65A, where multiple appliances are drawing 12kW (52A), attempting to charge an electric vehicle in FAST mode could cause the total consumption to exceed the grid limit. This could trip the supply or blow a fuse. However, by setting a Grid Limit of 60A, the zappi would automatically reduce its charging current to 8A (approximately 1.8kW), preventing the grid supply from being overloaded.
Proper installation and configuration of the Grid CT are non-negotiable for anyone looking to achieve optimal performance and safe energy management with their myenergi devices.
In summary, the installation of a Grid CT sensor is a critical safety requirement in any myenergi system. It ensures accurate monitoring of electrical currents, enables essential safety features like load balancing, and helps to maintain the overall efficiency and safety of the installation.