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Question 17/56
Do all residual current devices (RCDs) use the same operating principle?
Correct Answer: C
Residual current protection has evolved:
* ELCB (Earth Leakage Circuit Breaker): Older type; voltage-operated. It trips when voltage develops between earth and exposed metal.
* RCD/RCCB (Residual Current Device/Circuit Breaker): Current-operated. It detects imbalance between live and neutral conductors (indicating leakage current to earth).
Modern data centers use RCDs/RCCBs exclusively, since ELCBs are obsolete and unreliable if multiple earth connections exist. Thermal-magnetic breakers (D) provide overcurrent protection, not earth leakage.
Thus, not all residual current devices are based on the same principle.
References: IEC 61008, IEC 61009 (RCCB/RCD definitions), IEC 60364 (Electrical Installations - Protective Measures).
* ELCB (Earth Leakage Circuit Breaker): Older type; voltage-operated. It trips when voltage develops between earth and exposed metal.
* RCD/RCCB (Residual Current Device/Circuit Breaker): Current-operated. It detects imbalance between live and neutral conductors (indicating leakage current to earth).
Modern data centers use RCDs/RCCBs exclusively, since ELCBs are obsolete and unreliable if multiple earth connections exist. Thermal-magnetic breakers (D) provide overcurrent protection, not earth leakage.
Thus, not all residual current devices are based on the same principle.
References: IEC 61008, IEC 61009 (RCCB/RCD definitions), IEC 60364 (Electrical Installations - Protective Measures).
- Question List (56q)
- Question 1: In order to save energy, you are going to install an automat...
- Question 2: The logical overview of the data center looks as pictured. T...
- Question 3: A customer requires THDi from the UPS not to exceed 3% and w...
- Question 4: When are the wet bulb and dry bulb temperatures identical?...
- Question 5: EMF shielding material needs to be installed as EMF levels f...
- Question 6: ICT rack consumes 3 kW with #T ~11 °C (20 °F). Calculate req...
- Question 7: What is a significant difference between a halocarbon gas-ba...
- Question 8: Where should raised-floor installation start?...
- Question 9: Two servers stacked with no gap (metal-to-metal). What heat ...
- Question 10: A computer room with raised floor and hot/cold aisles is des...
- Question 11: The 'maximum exposed area' of the fire-rated glass is define...
- Question 12: What is a potential disadvantage of using a hypoxic-based fi...
- Question 13: When installing a raised floor, can we use a spirit level ba...
- Question 14: You are changing the design of the fire suppression system f...
- Question 15: Do you need to consider bullet (ballistic) protection when d...
- Question 16: An air-conditioner unit needs to be selected. Two types are ...
- Question 17: Do all residual current devices (RCDs) use the same operatin...
- Question 18: What indicates the breaking capacity of a fuse or breaker?...
- Question 19: What mainly affects the cooling capacity of a raised floor t...
- Question 20: A computer room needs to be fitted out with a gas-based fire...
- Question 21: The building in which the computer room is housed is require...
- Question 22: The UPS of a data center, with an ANSI/TIA-942 Rating-4, is ...
- Question 23: A data center has its own power supply from the public utili...
- Question 24: What indicates the overcurrent of a fuse or breaker?...
- Question 25: You need to install a highly sensitive fire detection system...
- Question 26: Should aerosol cleaning solutions be used in the computer ro...
- Question 27: What is the redundancy setup shown in the diagram?...
- Question 28: Smoke sensors must be installed in the computer room. What i...
- Question 29: Do you need to consider bullet (ballistics) protection when ...
- Question 30: The data center has been in operation for about 1 year and 2...
- Question 31: What is the focus of the Open Compute Project (OCP)?...
- Question 32: Racks with 1.0 m depth and cold aisle containment with 3 per...
- Question 33: Which formula is correct?
- Question 34: You have three UPS systems connected in parallel. The UPS sy...
- Question 35: What is the preferred way to measure dust levels in the comp...
- Question 36: How is the PUE ratio calculated?...
- Question 37: A data center scores Rated-3 in mechanical, Rated-4 in elect...
- Question 38: What is the floor loading requirement for a Rated-3 data cen...
- Question 39: The temperature in the computer room is being increased from...
- Question 40: Maximum exposed area of fire-rated glass is 2 m², but the wi...
- Question 41: What is the advantage or disadvantage of using MPO (Multi-fi...
- Question 42: What is the calculation for the desired attenuation factor f...
- Question 43: What is the minimum requirement for the power feeds to the b...
- Question 44: Does hot/cold aisle containment impact PUE?...
- Question 45: When designing a data center network, your company wants to ...
- Question 46: You are working with a customer who requires a guarantee tha...
- Question 47: Given: A = attenuation in dB, R = real measured value, M = m...
- Question 48: You need to determine the strategy for the cooling audit. Al...
- Question 49: What is the main disadvantage of using a ToR (Top of Rack) d...
- Question 50: You are allowed to use a calculator for this question. A com...
- Question 51: A battery bank has 800 Ah total capacity. How much charging ...
- Question 52: What is the main advantage of using an End-of-Row (EoR) desi...
- Question 53: In which stage of the data center life cycle does commission...
- Question 54: What is the main reason to install Earth Leakage protection?...
- Question 55: The UPS of a data center with ANSI/TIA-942 Rating-4 is insta...
- Question 56: A data center requires an audit to find out whether it confo...
