The earth leakage clamp meter is a very popular troubleshooting tool. It allows you to identify AC leakage current, which is a common problem that can trip RCDs, but is an unseen problem that the user might not be aware of. The TIS 570 earth leakage clamp meter allows you to identify this, and with a high degree of accuracy.
AC leakage arises when an electrical item is in operation, and can occur because the insulation around cabling or wiring is damaged, due to water ingress, or due to electromagnetic interference. This current leakage can occur even when the item isn’t being used, and can cause an RCD to trip and shut down the appliance. In such a situation, the first thing you should do is to assess the total leakage current within the installation, using a clamp meter.
The importance of choosing the right RCD
In most situations a 30 milliamp RCD is likely to trip if the leakage current exceeds 15 milliamps. Current regulations specify that nominal leakage current should remain below 30% of the RCD’s operating leakage current, so 9 milliamps for a 30 milliamp-rated RCD. This means that RCDs installed on individual circuits are an advantage and are more commonly seen on consumer units.
However the presence of more than 6 milliamps of DC current can ‘blind’ most standard RCDs.
DC current leakage can occur during the operation of various consumer units, or from faults occurring within power electronics equipment, such as washing machines, solar inverters, heat pumps or electric vehicle chargers. In all cases you need to ensure that the correct RCD is installed.
The award winning TIS 570 has the capability to measure both AC & DC leakage currents.
In the case of a three-phase heat pump – a more sustainable form of heating and hot water provision which is being seen as a green alternative to the traditional gas boiler and hence is increasing in common use – the heat pump is protected by an RCBO (a residual current circuit breaker with overcurrent protection) of type AC. Heat pumps contain variable frequency drives which can produce DC current leakage during their operation, but this information is not always known to the user and is often hidden only in the manufacturer’s data sheet.
How the TIS 570 gives great accuracy
Using the TIS 570 clamp meter, we can place this around all the live conductors and measure the leakage current while the heat pump is operating. This should generate around 8 milliamps of DC current leakage and so should be protected by a Type B RCD. However, it is not only high-powered appliances which produce DC current leakage, this can also occur with small appliances, for example a small circulation pump can also produce DC current leakage. It is common to see a series of small circulation pumps installed together, so the combined effect of these can produce a significant amount of DC current leakage, which might therefore require a Type B RCD.
Most clamp meters do not possess the accuracy required to measure small amounts of DC leakage, in terms of the resolution needed to detect precise measurements. However, the TIS 570 clamp meter has the ability to measure in tenths of a milliamp, which means it is suitable for identifying and measuring these small amounts of DC current leakage. The TIS 570 clamp meter is a critical instrument for identifying potential issues with diverted neutral currents. It will allow for regular current measurements of up to 10 amps in the DC range and 20 amps through true RMS ASC. In addition to this, the TIS 570 enables the user to measure voltage resistance and continuity in the circuit.
EFIXX Video:
Below is a video on EFIXX promoting advantages of TIS 570 AC leakage, but most importantly DC leakage clamp meter: