MK Sentry RCD 100A 30MA 230V DP Type A 2 Module

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Interesting Comments you are entitled to your view, but I am not sure about your motivations - as the article does not say that you cannot use Type AC RCDs.

Single-phase inverter designs, applied in washing machines and handheld appliances, containing variable speed features, may produce mixed frequency leakage currents. Appliances containing inverters and motors, can be used with Type A RCDs, if: ii) RCD Type A: RCD tripping on alternating sinusoidal residual current and on residual pulsating direct current, suddenly applied or smoothly increasing. To help explain, it might be worth thinking about some older models of earth fault loop impedance testers, which could cause the RCD to operate unintentionally. To prevent this, some types of earth fault loop impedance testers imposed a DC current on the AC test current. This DC current saturated the magnetic core of the RCD preventing it from tripping under the test condition. Some equipment will have DC leakage current by the nature of design, other equipment may produce DC currents during fault conditions, dictated by the construction of the equipment.The primary principle of an RCD is to protect the persons using the installation, if manufactures are going to be allowed to make equipment that is going to end up in peoples homes then British Standards must make it compulsory for manufactures to state in bold writing how that equipment will affect an installation where RCD's are present, it's already common practice for many manufactures to state what the maximum protective device is to be used with their equipment, so make it their responsibility. Many studies on the in-service reliability have been carried out on RCDs installed in a wide range of installations providing an insight into the effects that environmental conditions and external factors can have on the operation of an RCD. Key information: You might ask "Why are Type AC RCDs still referred to in the 18th Edition of BS7671, when most installations should be using Type A devices as a minimum requirement?" It should be noted that the residual DC leakage current can vary with motor speed and cable length. In a healthy circuit, the vector sum of the currents flowing in all live conductors should be nominally zero. When a fault occurs on a circuit causing a current to flow to earth, this creates an imbalance and trips the device. What is DC residual/fault current?

The initial verification required under 641.1 and 301.1 (ii), covers the requirements for the verification that electrical equipment (any appliance supplied or connected, as part of the existing fixtures and fittings) is compatible with other electrical equipment such as RCDs installed to provide additional protection e.g. for a domestic installation, document the appliance RCD requirements with the justification for the consumer unit specification. Type AC RCDs are in clause 531.3.3 of BS7671 2018, because they are still in EN 60364-5-53 2015. The UK have just adopted this line from the EN standard. The method of installation relating to protective earthing will depend on the operational leakage current (protective conductor current) – see 543.7. The use of a 30mA RCD may be required for several reasons; cable installation, location / application area for the pump etc. Take note of 531.3.2 Operational leakage current (protective conductor current) for the circuit should not exceed 30% of the RCD sensitivity. UK electricians can still make informed technical decisions. This is explained in Chapter 12, 13 and Chapter 30. The Electrician is responsible, not the Technical committee, to make the decision on which device is appropriate for the installation. The revised RCD guidance in 531.3.3 is precise. The appropriate Type of RCD must be selected, based on the characteristics of the residual current and the equipment that is likely to be connected to the RCD protected circuit. and the RCD should be selected based on the characteristics of the connected loads.

RCDs are far more sensitive than circuit-breakers. The sensitivity being rated in milliamps (mA) as opposed to amps (A). Different Types of RCD

Type A RCDs are used for alternating sinusoidal residual current and for residual pulsating direct current up to 6 mA. It is important to understand that RCDs cannot limit voltage or current, they provide protection by limiting the time a specific maximum current can flow to earth. Residual Current Device is a generic term used for describing devices which incorporate residual current protection in accordance with one of the standards below:Where electric vehicle charging equipment is likely to create a residual DC fault current, manufacturers may provide the correct type of RCD within the charging equipment. However, problems could arise if the charging equipment is installed downstream of an existing Type AC RCD, which could be blinded by the residual DC fault current. In some types of DC charging equipment, the AC input side is galvanically isolated from the DC output which, hence, provides electrical separation. This means that faults on the DC output side, connected to the vehicle, would not be detected by an RCD on the input side of the circuit. What are the hazards and problems? The cost of a Type A RCD is more than an AC Type and, subsequently, B and F Types are significantly more than that (currently hundreds of pounds) therefore it is important to understand the requirements or a significant amount of money could be wasted. What are the different types of RCD? The revised RCD guidance in 531.3.3 is precise. The appropriate Type of RCD must be selected, based on the characteristics of the residual current and the equipment that is likely to be connected to the RCD protected circuit. I believe the article makes it clear that the their are 4 Types of RCD that may need to be considered - Quote from the article -

Commercial installations comprising LED lighting and large quantities of IT equipment which can also cause other issues, such as protective conductor current which should also be considered. An RCD monitors the earth leakage current in a circuit. It is constructed from coils of wire wound around a ferrite toroid core, one for each live conductor of the circuit protected. When a current imbalance between live conductors is detected, a voltage will be induced in the tripping coil which will disconnect the electrical supply to the protected circuit (see Figure 1). NOTE 4: For guidance on the correct use of RCDs for household and similar use, see PD IEC/TR 62350. Add to that the changes that have been imposed on the local supply networks i.e. green energy they have caused a situation that is going to result in frequent surges and transient voltages being produced all the time hence we now need to install surge protection or the likelihood is that if a surge occurs at a property and there is no surge protection then the blame will be passed on to the little man again. Type F RCDs cannot provide protection in circuits where there is a requirement to detect smooth DC residual currents, or if the motor frequency can be reduced to zero or the inverter switching frequency is >1kHz. If any of the above conditions apply, Type B RCDs must be used.For single phase inverters used in motor speed control, the characteristics of the equipment will determine if Type A, F or B is required, to meet Regulation 531.3.3 For 3 phase inverters which do not incorporate isolating transformers, Type B RCDs must be used to meet the requirements of Regulation 531.3.3 For additional information. So - please help me - have I lost touch with the right places to buy RCDs in the UK? Where can one get a fairly broad selection of different types (A, B) at reasonable price? Why do I find almost entirely AC? If the inspector is concerned that residual DC current may affect the operation of Type AC RCDs, the client must be informed. The client should be informed of the potential dangers which may arise and an assessment of the amount of residual DC fault current should be made to determine if the RCD is suitable for continued use. Depending on the amount of residual DC fault current, an RCD which is blinded by residual DC fault current is likely not to operate which could be as dangerous as not having an RCD installed in the first place. In-service reliability of RCDs All types of electrical installations could be affected, it depends on the equipment which has been installed. Examples include: i) RCD Type AC: RCD tripping on alternating sinusoidal residual current, suddenly applied or smoothly