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RCDs on electric gates
RCDs on electric gates
RCD protection on electric gates can cause problems. What measures can you take to help?
Author ; Huw Jones
Why electric gates need an RCD
Gate systems work in the wet, so any water that gets into the electrics is a potential shock hazard. But when they trip out,
Their purpose is to protect mains circuits. Outdoor cirrcuits are covered by Part.P of the building regulations which will need an RCD.
What is an RCD?
Residual Current Devices (RCD), are found in a fuse box. They look like a resettable fuse, but have a button marked 'test'. Their purpose is to protect mains circuits in vulnerable areas where insulation damage could render metalwork live.
A 30mA RCD (0.03 amps) will protect a human from death by electricution. A 300mA RCD (0.3 amps) may be used for heavy equipment and fire protection.
Some properties are covered by a single RCD trip. We advise the gate be on a separate parallel 30mA RCD so that any outdoor faults do not trip out the whole house.
How does an RCD work?
In simple terms, all the power that flows out of the 'Live' terminal should flow back through the 'Neutral' terminal. If there is an imbalance, some current is being lost somewhere else. Think of it like a water circulating around a pipe. A leak in the pipe will result in less water coming out of the pipe than went in. The RCD measures the difference between currrent through live and neutral. For more info, see ...
https://www.electricalsafetyfirst.org.uk/guidance/safety-around-the-home/rcds-explained/
Isolating the problem
It is easier if your gate system is protected by a dedicated 30mA RCD. The RCD trips on a total leakage of 30mA contributed by all the items on that circuit. Too many times, the RCD also supplies outdoor lighting, pool pumps, electric vehicle chargers, CCTV and intercoms. Worst case, it trips out the whole house!
You first need to know what else is connected to the gate RCD. Press the test button to kill the power, then check what else has been cut off. Isolate all but the gate, then see if the RCD trips when the gate motors are run. If not, the gate system failure is not a single fault, but an accumulation of leakage.
If a double leaf gate trips the RCD at the point of run, disconnect each motor in turn at the control panel. If each motor runs on its own, the fault is an accumulation of leakages. Remember, all the wiring up to the motor is included in the test.
One motor might be directly connected, but the far side motor will have a junction box in between the motor and the control panel. Locate the connection, disconnect the motor, and try the test again. If you can't find the junction, it maybe underground, and there lies your problem.
Sloppy installers sometimes leave the junction box in the underground motor casement that often causes problems. There are gel filled connector box products that make promises to the gullible. The installer forgets that the IP rating needs to allow for changes in air pressure. The air in the motor heats and cools causing pressure changes that can suck water in over time.
RCD's on an electric gate
Your gate system should use a dedicated 30mA RCD. You first need to know what else is connected to the gate RCD. Too many times, the RCD also supplies outdoor lighting, pool pumps, electric vehicle chargers, CCTV and intercoms. Worst case, it trips out the whole house! Press the test button to kill the power, then check what else has been cut off.
The RCD only trips on mains powered loads. Gate system controllers for 230Vac motors generally isolate the motor Live and Neutral feeds until the motor is required to run. If there is a current leakage fault in the motor or mains flashing light or courtesy lights, the breaker will not trip until the motor tries to run. The control panel and intercom supplies are connected all the time. There may also be timed lighting.
The RCD can be positioned in gate control panel, or in a nearby waterprrof enclosure. The supply cable up to the RCD should be suitably protected if not under RCD protection, and the supply must be fused.
Conclusions
- Wire the gate system RCD to a spur from the house supply under its own MCB
- Do not use the gate's RCD protected supply for other outdoor equipment
- Use only direct burial cables below ground. Protect duct entrances against rodent.
- Underground joints are unreliable. Underground casements must have good drainage
- Instal control panels in a waterproof enclosure or nearby building such as a garage