What’s the Difference Between an ELCI and an RCD?
European and US boats carry slightly different equipment to protect against electrical problems.
December 12, 2014
Question: I’m the proud owner of a new European-built Hanse cruising sailboat. I love the boat and now that the season is over for me I’ve been spending some time studying all of its features.
One of the things I noticed with my shore power system is the safety device the Europeans use to provide over-current protection and I think shock hazard protection for the shore power whenever the boat is plugged in at a dock.
An RCD, or residual current device, provides over-current protection on some European-built boats, similar to ELCI devices on US-built boats.
My dock neighbor has a two-year-old boat with US-made electrical gear installed and his shore power system is equipped with an ELCI device. Can you tell us what the difference is between the devices? And what do they call the device used on my Hanse?
Answer: In the photo you provided [below] of your friend’s ELCI, also known as an “equipment leakage circuit interrupter," you are looking at a device that has a nominal trip rating of 30 mA and it is combined with a circuit breaker that is intended to provide overcurrent protection for the shore power system at a nominal 30-amp level. This is all pretty much standard equipment on newer boats here in the US and is one of the requirements found within ABYC Standard E-11.
An ELCI monitor on a US-built boat.
The device on your Hanse, (an “RCD” or residual current device) is providing the same protection at slightly different levels of 22 mA and 40 amps respectively. The device in your photo does not align exactly with the specifications found within E-11, but I’ll bet it matches with ISO requirements to achieve CE mark. Both of these devices provide both shock hazard protection and overcurrent protection. The shock hazard protection is achieved by shutting down the power to the boat when a short circuit to ground is detected. Common sources for these sorts of shorts are things like electric water heaters, refrigeration or air conditioning motors, and failed battery chargers.
In either case, these devices are similar to the GFCI devices you should be familiar with in kitchen, bathroom, and outdoor power outlets at home, with test and reset capability to ensure they still function. Many of these devices will have “test monthly” embossed on their face. This is a good idea to make sure the mechanical mechanism inside the device is in good working order. This is especially true in the saltwater environment, where corrosion is our worst enemy.
