Part 1e: TERMINAL BLOCKS

by Cameron Clarke

Electrically it looks something like this:

Figure 4, Barrier Strip Series Connections

Each link will add about 0.09 ohms of resistance if well made. I have shown 6 links to get from point "a" to point "g". That results in 0.54 ohms between points "a" and "g". We call this a series string. To make the panel look nice, the feed point would be point "a". It would look messy if it were the middle, point d, so point a is often the feed. If the circuit breaker or fuse of your bilge pump were connected to point "g", then 5.4 amperes would flow through each link in the series string. Right? Yes! And 0.54 ohms times 5.4 amps result in a 2.9 Volts drop just across the series link! Now add that to the 3.24 volt drop from the wiring network and see if the pump works very well! A series string is bad because of all the added connections. There are preformed strips, one piece of metal with many fork-like terminals that are made to use in place of the wire links. Remove the links where possible and use the preformed strips. Any questions?

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Photo 1, Barrier Strip with Interconnecting Links

Photo 1 shows an example where a production boat manufacturer has used a barrier strip with many interconnecting links to simulate a buss bar. While it may look tidy, it is nothing more than a strip of series connections. Take this as an example that should be corrected. This is an application for a buss bar. Notice the congestion of fork terminals on the left side as the owner added more circuits. In addition, a couple of the terminals were crimped with the incorrect tool. No terminals in the photo are ring terminals. Replacing the barrier strip with a suitable buss bar would reduce voltage drop and look neater. Replacing the fork terminals with ring terminals properly crimped and soldered would prevent many problems surely to develop in the future otherwise.

One can relocate the load point for larger amperage devices close to the feed point. Ham or VHF radios, electric pumps and refrigeration all benefit with connection close to the feed. You can increase time between battery charges just by moving a connection or two, thereby reducing wiring network losses. Does this make sense? Sure it does, if you can reduce your wiring loses by 8 to 10 percentage points, its the same effect as adding as much capacity to your batteries. In addition, the range of your radios will be increased and most likely last longer.

click to view the Introduction and Table of Contents		A few boats have buss bars, copper bars with many screws for securing ring terminals. These are much better electrically than barrier strips. Buss bars are designed to make many connections at one voltage potential and very little interconnection resistance. They do that very well. Barrier strips were made to make many independent, non-interconnected connections appear neat. They do that very well. Some builders have not realized the differences in application. I wish all boat manufacturers would use a combination of buss bars and barrier strips to make up their electrical panels (often pre-made outside the boat) and solder each crimped terminal for lowest possible resistance and longevity. The panel should be designed with strong posts to attach heavy gauge positive and negative wires to the battery. I really like the use of distribution panels, because they are neat and place all the electrical distribution in a common location. However they add a considerable number of extra connections in the wiring path and are often the source of many loose or poorly made crimp terminals. Extra care need be taken to make the panel a true asset. Hint: If you have them aboard, take some voltage drop measurements within your distribution panel and barrier strips.
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