RCDs (Residual Current Devices)

RCD types, trip current ratings, installation requirements, and testing obligations for UAE construction sites, site offices, and welfare facilities.

Mandatory RCD Protection

Residual Current Devices (RCDs) are mandatory on all UAE construction site electrical installations. The Abu Dhabi DoE EWR 2020 (Section 9.5) and the Dubai Building Code 2021 both require RCD protection on all socket outlet circuits, portable equipment circuits, and outdoor circuits on construction sites. ADOSH-SF CoP 15.0 reinforces this requirement as a critical control measure against electric shock fatalities.

Socket outlet circuits
RCD ≤30 mA — mandatory on all circuits
critical
Portable equipment circuits
RCD ≤30 mA — mandatory
critical
Outdoor circuits
RCD ≤30 mA — mandatory
critical
Lighting circuits (site)
RCD ≤30 mA — mandatory
critical
Fixed equipment (>32A)
RCD ≤100 mA or 300 mA (fire protection)
standard
TT earthing system
RCD mandatory on ALL circuits
critical

RCD Types and Selection

The correct RCD type must be selected based on the load. Type AC RCDs respond to sinusoidal AC residual currents only. Type A RCDs respond to AC and pulsating DC residual currents (required for circuits with electronic equipment, VSDs, and IT equipment). Type B RCDs respond to AC, pulsating DC, and smooth DC (required for circuits supplying frequency inverters and EV chargers). On UAE construction sites with significant electronic equipment, Type A RCDs are the minimum requirement.

RCD Type	Detects	Typical Application	UAE Requirement
Type AC	Sinusoidal AC only	Simple resistive/inductive loads	Minimum for basic lighting circuits
Type A	AC + pulsating DC	Electronic equipment, power tools, computers	Minimum for site offices and welfare areas
Type B	AC + pulsating DC + smooth DC	VSDs, EV chargers, solar inverters	Required for generator AVR circuits, VSDs
Type S (selective)	AC — time-delayed	Main incoming RCD (discrimination)	Required at main DB for discrimination

RCD Testing Requirements

RCDs must be tested at regular intervals to ensure they operate correctly. The test button on an RCD only confirms the mechanical operation — it does not verify the trip current or trip time. Proper testing requires an RCD tester that applies a known residual current and measures the trip time.

Test button check
Monthly minimum — press test button, confirm trip
critical
Instrument test (trip time)
At commissioning and every 6 months — RCD tester required
critical
Trip time — 30 mA RCD
Must trip within 40 ms at rated current (IEC 61008)
critical
Trip time — 100 mA RCD
Must trip within 200 ms at rated current
standard
Test records
Written records of all RCD tests retained on site
critical
Failed RCD
Replace immediately — do not continue using a failed RCD
critical

ADOSH-SF CoP 15.0 requires that RCD test records are available for inspection by the authority at any time. A failed RCD that has not been replaced is a prosecutable offence under UAE OSH law.