Well Grounded

Maintenance Q & A — November 2001
Maintenance Q & A — November 2001
By Capt. Ken Kreisler

Well Grounded
The importance of ground wires in an A.C. circuit, caring for isinglass, and more.
 More of this Feature
• Part 1: Ground Wire, Isinglass Care
• Part 2: Diesel Exhaust, Amine Blush Removal, and more

 Related Resources
• Maintenance Q&A Index

How does the grounding wire in an A.C. circuit protect against electrical shock? P.L., via e-mail
Coming in contact with a hot wire while standing on a grounded, conductive surface will allow your body to become a parallel return conductor to ground and result in you experiencing an electrical shock. The ground wire provides the current with an alternative low-resistance return path to ground.

The accompanying illustration explains how this works. In the first diagram we have an A.C. motor hooked up to a two-wire system: hot (black insulation) and neutral (white insulation). Both wires are supposed to be isolated from one another as well as from the metal case of the motor. However, let's assume that the hot wire's insulation has failed and so the conductor is in contact with the metal motor casing. The motor will continue to operate normally, but since the casing is "hot," coming in contact with it will produce the same result as touching the wire itself.

In the second diagram, a ground wire (green insulation) is connected to the neutral wire at the power source and runs  parallel to it throughout the system. Connecting this wire to the exterior of the metal case of every electrical device--in this case the motor--in the circuit will offer the stray current a low-resistance path to ground. Furthermore, should the short be of low enough resistance, the current will trip the circuit breaker or blow the fuse of the black conductor. (For this reason, never install a switch, circuit breaker, or fuse in the green grounding conductor.) But even if the breaker or fuse doesn't trip or blow, the green wire will still provide a safe route back to ground.  

What is the proper way to care for isinglass, and how can I protect the zippers and snaps? K.P., via e-mail
Wash your isinglass panels before you roll them up to prevent dirt and salt from scratching the surface. Simply hosing with fresh water and drying with a clean chamois cloth will do the trick. I've found that using products such as Meguiar's Mirror Glass #17 or Star brite's Plastic Polish Restorer after a thorough washing works well as these form a protective layer that surface dirt doesn't easily adhere to.

For isinglass that is already scratched, try Star brite's Plastic Scratch remover. It will gently rub out the scratches, after which you can follow up with polish. And remember, once isinglass turns brown or yellow, it must be replaced.

As far as keeping snaps and zippers working properly, frequent freshwater dousings will help to remove salt buildup, especially after tying up for the day. A little WD-40 applied with a cotton swab usually works well.

For added protection, I've used Star brite's White Teflon Snap & Zipper Lubricant on Office Ours, PMY's company boat, and found that a once- or twice-a-season application keeps things running smoothly. All these products are available in most marine supply stores.

Next page > Diesel Exhaust, Amine Blush Removal, and more > Page 1, 2

This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.

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