30 Amp Smart Plug Assembly

Last week I found myself at one of my favorite "ends of the earth" as I often refer to such places, Astoria, Oregon. The town is somewhat notorious for several reasons. One, the entrance to the Columbia river is located here. Two, it is a major pacific port for some of the boats that you are likely to see on tv shows like the "Deadliest Catch". they have a fisherman's memorial right in town for all of the fiherman lost at sea that drives home the whole "deadliest" side of offshore fishing.

Astoria is also home to one of my favorite marine chandleries here in the US, Englunds. While walking the aisles I of course ended up in the electrical department and found one of the items that I have been following for the last several years, The Smart Plug.

Now the purpose of my visit to Englunds was to conduct a safety inspection course that I have developed for our friends at NOAA. We were walking the aisles looking at equipment that the students in the class would be required to inspect as part of their small boat inspection program. Of course, faulty shore power installations are among those things that require annual inspection under the NOAA mandates. So, one of the students asked a really good question, why doesn't the ABYC allow Smart Plugs? They make so much sense after all. Good question! Easily answered, but in answering the question, the point that Standards don't always get it right gets raised. This whole matter is one where an ancient industry Standard is now stifling technological innovation in my humble opinion.

It seems that somewhere way back when, the ABYC wisely referenced a UL Standard to apply to shore power cords. Something we at ABYC do all the time. Unfortunately the specific UL Standard has a requiremnt for a "twist lock" feature for these plug assemblies. The idea here was to require a locking method that would minimize the risk of a shore cord partially backing out of it's socket. A good idea and certainly well meaning, but now represents "old tech".

The sad truth is, as these plug and socket assemblies wear, the twist lock feature gets a bit sloppy and frankly just doesn't work very well. The net result of this has been shown visually here several times, but just in case you've forgotten, the photo below shows what can happen....

The photo above was taken with a thermal imaging camera. The yellow glow is heat being generated. You are looking at a typical 30 amp shore cord plugged into the side of someone's boat. As the heat builds up a fire potential is very real.

So, the Smart Plug deals with all of this rather effectively. Its got a spring loaded multi-point push lock arrangement that really does a much better job of keeping the plug in place. The plug also has watertight sealing which will help take care of the corrosion issue that is common to existing old tech assemblies.

The plug blades have much more surface contact area which will reduce electrical resistance, and remember, as I've said here many times before the primary by-product of electrical resistance is heat!

So where are we in the Standards compliance arena with these plugs? Well, late last year the company did gain certification and gained an ETL listing. Most readers will have no idea what that means. You are all used to seeing the "UL" listing. Guess what, the ETL listing is just as good. As for the twist lock issue, Smart Plug is still forced to use that stupid twist lock on the dock end of the shore cord for now. The company does plan to work out any additional compliance bugs during this year and hopes to be able to offer kits for retrofitting the shore end of the assemblies by the end of this year.

The bottom line here? This is a better idea in my view. Just have to get past the Standards hurdles. The National Electrical Code folks need to do a little soul searching and updating on this one in my humble opinion.

 To learn more about the ETL listing process, go to: www.intertek.com

To get more detailed information about the Smart Plug, check out www.smartplug.com

Yesterday we finished up with the ABYC Electrical PTC meeting and I walked away feeling though some of the most important issues facing the technical side of boating had been resolved.

I'll give you a brief update on some of the specific issues we have put some new or revised standards language in place on here with a promise to follow up with more detail as the final language gets ready for publication. I think it is important for people to understand that this is a long difficult process and for a guy like me that has made the whole process a career and passion, I'm feeling like the committee made some significant progress this week.

So, here's the recap:

We have finally developed language that will require overcurrent protection for DC electrical systems that are connected to very large, super high current potential battery banks. This language, when finally written into the Standard will provide for some of the new battery technologies like Lithium-ION and thin-plate pure lead AGM and whatever comes at us next from a technological perspective. The bottom line here is that we now have batteries in use on boats that have the punch to create enough energy to do serious damage if not properly controlled. ABYC has now built in some controls.

We have been increasingly seeing high current DC loads getting integrated onto boats. One of the problems boat builder's today have to grapple with is wire routing through the boat. This often means that wires get bundled and sometimes those bundles are quite large and buried in the boat structure. This can create heat problems for the wiring. Well, one of the contributing factors in the creation of this heat is amperage. So, ABYC has now developed a new set of wiring and bundling tables that in some cases are going to derate wire amperage handling capabilities further than we have in the past. This is a good adjustment that is truly centered around changing needs of modern boaters, meaning that their "appetite for amps" as I have stated for some time just keeps going up.

Finally, the committee, after a battle of philosophies about shore power delivery systems that has gone on for at least ten and more probably fifteen years has approved the use of what are known as high-frequency switch mode transformers in shore power systems. Now to the average boater this means nothing, but for those familiar with transformer design issues you know where this is going. I am of the belief that more boat builders would be inclined to use what we know as isolation transformers if they didn't weigh so much. Well by finally allowing the use of the high-frequency units we have now opended the door to units that are approximately 4X lighter in weight than any previously compliant transformer.

So, there is a brief summary of where we have gone on the electrical side this week. We have other groups here looking at issues with fuel systems, and that is really a continuation of issues dealing with EPA mandates. We are looking at matters involved with navigation lights, and certainly LED lighting is falling into that picture. Later today, I'll sit in on some meetings that are looking at matters related to engine control systems. This is key stuff as we move more and more into the "fly by wire" approach on new boats.

Stay tuned, this is a big year for standards evolution as it applies to your boat. I promise to share as we start getting things into print. 

Its hard to believe that a year has just slipped completely past me. It seems like just last week I was writing to you all about ABYC Standards week 2010. Well, next week I hit the 2011 edition of Standards week so I though I might just share with you some of the broad topics I'll be trying to get the latest info on and throwing my 1.5 cents worth at.

Fuel systems is on-going as the EPA mandates for control of evaporative emissions from boats moves forward. To my knowledge the way forward on this topic is now pretty well cut in stone, but I will definately give you an update as things unfold next neek.

On the electrical side of things we have a really full plate. Some of the issues we are grappling with deal with wire sizing and derating based on bundle sizes and defining intermittent vs. continious loads in recreational marine terms.

We will be looking at issues related to the increasingly large and powerful battery banks we are beginning to see in either full or hybrid electrical systems on boats. Are properly protected in the event of a short circuit at or near the battery bank? some of us in the group think not.

We will also be looking at an issue that has been near and dear to my heart for some years now. We may actually finally approve the use of shore power transfomers that operate at high-frequency at ABYC Standards week. Now I know that means nothing to most of my readers, but if approved, rest assured I'll provide plenty of explanation here on how and why this is a really big deal to you. So for now, over and out. I need to get ready to head off to Orlando next week. I'll be reporting live from there as things unfold next week.

Continuing on the topic I started Monday where I discussed AIC rating and the phrase "short circuit current", let's dig in a bit deeper into the higher voltage DC issue / concerns I mentioned, since we are stating to see higher voltage DC systems more and more on boats, either as part of a hybrid propulsion system or to just simply reduce wire gauge sizes. (Note: use of higher voltage allows the use of smaller wire and cabling to carry the same amperage. In other words, at 12 volts if you need a 4 gauge wire to carry a certain amount of amperage safely, at 24 volts, you could carry the same amperage with a much smaller gauge wire.)

So, regarding the matter of AIC ratings for fuses and circuit breakers, the confusion lies in the fact that the AIC ratings for a given device are tested to specific voltage values, and the actual AIC will vary dramatically based on tested voltages. As an example, the heavy-duty class T fuse shown below has a 20,000 amp AIC rating, but that is at 160 volts DC, not 12 volts DC which is of course more common. In this case the issue is all good news for users. Why? Well because as system voltage decreases actual AIC ratings increase, quite considerably. At 12 volts, the actual AIC for a class T fuse will be over 100,000 amps!

This fact holds true for all devices but the problem is that the tested voltage values varies. For example a common ANL fuse type is rated at 32 volts DC and has an AIC of 6000 amps. Its rating at 12 volts will be higher, but not five times as in the class T example.

So, with the exception of the very large battery banks mentioned in my Monday post, which can have a huge short circuit current potential, where you may actually need that hidden reserve of the class T fuse at 12 volts, we are probably in pretty good shape with most boats and circuits, simply because 12 volt DC systems have been prevalent for decades.

Now however, we see this movement toward higher voltage DC use on boats and this means that the published AIC ratings for fuses and circuit breakers are going to start becoming more real. A class T fuse on a 48 volt power pack that is created from a Lithium cell with an absolutely off the charts short-circuit current potential may be at risk!

So you ask, well Ed what is the answer to all of this? Ed's answer at the moment is I'm not sure... The ABYC electrical committee is going to be meeting in two weeks and I'll be in attendance. This is an issue that myself and some of my colleagues are going to be presenting to the committee. At this juncture, the only safe protection I can envision is a limit to how many batteries or cells can be overcurrent protected by a given protection device, whether fuse or breaker.. Some lithium battery vendors are doing this now, others are not. Should there be an industry standard in place to mandate this? I think yes, but we'll have to wait and see. 

As promised just before the New Year I'm going to begin an educational series here so that more people will have an understanding of some of the concerns and potential issues associated with what I will refer to as "new tech" batteries and the application of higher DC voltages in marine systems applications. As I off handedly mentioned in my pre-New Year post, this is good stuff, but it all must be handled very, very carefully to ensure on board safety.

So, let's start out with some simple concerns related to higher capacity battery banks. I'm talking here about battery banks that look like the one shown here and larger:

 Today's two new terms are "short circuit current" and AIC, which is the acronym for "ampere interrupting capacity".

When I see a battery bank like the one above I immediately think of how much electrical current could potentially be unleashed in the event of an electrical short circuit anywhere near this battery bank, for whatever reason.

Here's what you the reader need to grasp here related to short-circuit current potential: A "shorted" lead acid battery has the capability of delivering anywhere from 100-1000 times the typical discharge current used in most electrical circuits on your boat.

Also, understand this, the effect is cumulative depending upon how many batteries are connected in a parallel configuration as shown above. There is some electrical resistance in the connections and wiring between each battery, but not much.

 In the photo above you are looking at 5 Odyssey batteries paralleled. Now I can't remember exactly which model Odyssey batteries they are as I took that photo about a year ago, but they look like they could be Odyssey model 31 M's. If that is the case, and we'll assume they are you are looking at what Odyssey will tell you is a potential 25000 amps of short circuit current available at the end of the string. You see Odyssey is one of the few battery companies that actually publishes this ever more important information in their specification tables. Hats off to them! We want more vendors doing the same! Check it out at www.odysseyfactory.com

So, term # 1 for today's lesson: Short Circuit Current

Now let's look at term # 2, AIC rating. This is a very obscure rating that implies how much electrical current a fuse or circuit breaker can be exposed to without literally welding the contacts in the case of a circuit breaker, or in the case of a fuse, turniong into a solid mass of metal. What does this mean to you the boater? The device won't function as intended and stop the electrical current flow..... Are you starting to get the picture here? Do you want 25000 amps of electrical current running through your boat's electrical system? Just say no to that thought, but understand that the AIC rating of fuses and circuit breakers, although an obscure value is really, really important, especially as we move to larger battery banks on our boats to meet all of our electrical load demands.

Tomorrow, I'll talk about the effect of high DC voltage on AIC ratings so come back again.