Another way to gauge electrical status

Sometimes you need to tear everything down to see things from a new perspective. That’s what happened to electrical engineer George Sotiriou when he decided to rebuild the electrical system on his 1986 Tayana 42, Mustard Seed. Ripping out the boat’s wiring harness not only gave an opportunity to redesign the system to his liking, he also got an idea for a new and improved way to indicate the status of electrical devices on board.

His system is based on a smart indicator light he calls a load status indicator. Sotiriou now sells these sensors, called the LSI-55, through his company Trident Instruments, Inc. through his Web site

Using a pilot light to indicate the status of an electrical device on a circuit breaker board is not new, of course. What’s different about Sotiriou’s LSI-55, however, is its ability to provide more information than a standard indicator light. The LSI-55 can show if power is available to an electrical device, but it can also show if the device is actually drawing power.

The idea for the LSI-55 came in the winter of 2006. Sotiriou had Mustard Seed on the hard and was pruning back its electrical system. He took out the existing electrical panel and cut the original wires back as far as possible and labeled them. According to Sotiriou, “you never realize the amount of wire that comes and goes on a boat of this size until you’ve filled up a 55-gallon drum with scrap wire.”

His next step was to redesign the boat’s electrical distribution system. He decided the long cables from the batteries to the panel at the navigation station resulted in excessive voltage drop. A location closer to the batteries was best, but the only possible space to put a distribution panel was a bulkhead adjacent to the battery compartment. In this way he could reduce the power cable lengths as much as 75 percent compared to the previous distribution panel at the nav station.

There was only one problem with this location, however. The companionway ladder blocked Sotiriou’s view of the bulkhead. He decided to go ahead and use the bulkhead, but to mount two circuit indicator lights — one at the bulkhead distribution panel and one at the nav station panel.

While redesigning his system, Sotiriou began to think about what he saw as the drawbacks to the standard pilot light approach. When a pilot light is off, is that because the circuit breaker has been put in the off position, or because the breaker tripped due to an electrical fault? Sotiriou also realized that he could not use the standard approach of using an ammeter mounted on the nav station panel to determine which device was drawing power. Standard practice is to turn off each circuit breaker one by one until the current draw on the ammeter drops, indicating which circuit is drawing power. With the circuit breakers mounted away from the nav station this becomes a more involved process.

Sotiriou decided what he needed was a device that not only indicated when power was available, but also when the load is active. This set Sotiriou on a six-month cycle of designing and prototyping. Eventually, he was satisfied with his new smart indicator light and called it the LSI-55. The unit illuminates with a green light when power is available and illuminates red when the load is active. Capable of operating from 10 to 300 volts AC or DC, it draws only 10 milliamps and can be used on a boat’s DC battery side and AC genset/shorepower side.

“This is an absolutely new device, with two patents,” Sotiriou said. “The technology has gotten to a point where a device like this is possible. Five years ago the technology to do this didn’t exist.”

On his boat Mustard Seed, Sotiriou equipped the distribution panel under the companionway ladder with a full set of LSI-55s, but he also used No. 24-AWG signal wire to connect the distribution panel units to a second “repeater” set at the nav station. Sotiriou says that at a glance he can see which circuits have power and which are actually active by seeing whether the LSI is illuminated green (power is available) or red (load is active).

A good example of how effective these indicator lights might be is a bilge pump, which generally sits low down and inaccessible in the boat. If the engine is running or you are sailing in a stiff breeze, you often can’t hear it. “Bilge pumps are really down deep,” Sotiriou said. “You really don’t know if it is running or not. If the LSI turns red, you know it’s running.”

At $24.50 each for the basic LSI-55, equipping a panel of 36 devices with LSI-55s will cost roughly $882. LSI-55 units with more advanced capabilities, such as for use as a remote pilot indicator and/or data module, or for use where the load is isolated from the supply power, cost from $28.50 up to $32.50.

By Ocean Navigator