MAILBOX: Hydro System Upgrades

New photo showing corrections made
New photo showing corrections made

Thank you for forwarding the comments from Michael Lawley that were published in Home Power’s July/August 2015 issue. We provide responses to Mr. Lawley’s concerns related to our hydro-electric system below. Mr. Lawley is hardly unique in his concern for safety—we are all doing the best we can.

Concerns: The turbine’s magnetic rotor is not covered and is a rotational hazard. Lacquer copper wire is not classified as insulation for touch safety. Exposed copper stator wire is clearly visible and could be touched when operating.

The turbine is in a locked building and does not present a realistic rotational hazard nor is the stator wire exposed to any but the owner/installer. Note that this system is so weak that the rotor can be stopped by hand without any risk of injury. We understand that others might consider this article a general guide, and more powerful systems might present a realistic risk. Therefore, in the interests of extra safety, we have revised the installation to include a removable cover for the rotor, which addresses both of these concerns.

Concern: The resistive diversion element is bolted to a plywood wall without any heat shield. This is a fire hazard and not allowed under U.S. standards/codes.

This is an excellent point. We installed a heat shield, with an air space between the heat shield and the wall, after the article was finalized, but before it was published.

Concern: According to the wiring diagram, the metal turbine body has no earth connection and, under a fault condition, could become a shock hazard. As the turbine is mounted on a plywood cover, it appears to have no earth connection.

The turbine is mounted on a steel cover and has an earth connection through the vertical steel culvert. Based on Christopher Freitas’ article in HP160, we agree that an additional ground is needed to protect the electronic components. Therefore, in the interests of making the need for a ground clearer, a ground wire was added, connecting all the components of the Pelton system to a grounding rod outside the microhydro system’s building. Note that the grid-tied main system, several hundred feet away, is independently grounded.

Concern: The photo on page 63 shows a red positive wire to the TriStar TS-45 and a green (assumed to be the negative, as there is no other wire) to the TS-45. Green wire cannot be used for negative connections.

With the greater focus on combined DC and AC circuitry, we understand that there has been a move away from using green as negative in DC systems. Therefore, in the interest of conformity, we replaced the red and green wire with 2 AWG Romex.

Concern: The TS-45 is not wired in per the manufacturer’s advice. If the fused disconnect was opened while the turbine was running (or the fuse was to blow), the TS-45 would be damaged by overvoltage.

We were attempting to use the TS-45 to keep the turbine from overspinning when disconnected. I gather now that this is an inappropriate use and have revised the wiring to connect it directly to the batteries, using it as a diversion load only. We note that Mr. Lawley’s advertised system uses a crowbar three-phase shorting unit to control overspeeding with disconnect, which sounds like a very good idea, but we don’t know how to obtain such a unit for our system. For now, we have to remember to shut off the water before shutting off the electrical system.

Concern: To comply with the intent of the National Electrical Code, hydroelectric systems using a diversion controller should be equipped with a second independent means of charge control to prevent overcharging the battery in the event of a component failure.

The National Electrical Code has language that states requirements for diversion controllers used in PV and small wind power systems. It does not specifically address their use in microhydro systems. However, we note that best practices for a standard installation would include a second independent means of regulating the battery charging, even in a grid-tied system like ours, for backup if the grid is not available.

Penny & David Eckert • Orleans, California

Thanks for the detailed response, Penny and David. More importantly, the immediate action you took to address your hydro-electric system’s safety and Code compliance issues is impressive! We’ve updated the online version of your article in HP167 to reflect the upgrades you made to the system. Home Power’s main goals are to increase the use of renewable energy systems, as well as improve their performance and safety. This is a great hands-on example of how, collectively, our community can do just that.

Joe Schwartz • Home Power executive editor

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