Check those shore power connections!

[twistedtree]

No, the wires in the boat are not the weak link if the boat is wired properly. The L5-30 plugs are the weak link. The contact area is just too small and if you run much over 25 amps they tend to overheat and get worse as time goes by. The wiring in the boat has permanent connections so they don’t overheat if the wire is sized properly and has overcurrent protection. If the boat isn’t wired properly then all bets are off but that isn’t typically the case.

I'm curious who says the contacts are too small, other than Smart Plug? NEC and UL don't seem to think so. I don't doubt that the Smart Plug contacts are larger, but what's the basis for saying the NEC contacts are too small?


Now it may seem like I'm defending the 30A NMEA plug, and I'm not really trying to. I think it sucks, but more because it doesn't secure well enough for a marine application where constant movement can be expected. Those locking rings are a joke. I don't think I've ever been successful at getting two to mate together and do anything useful.



I'm just challenging the assertion that the contact area is "too small". Based on what?


And to Xsbank's point about the "Smart" in Smart Plug being a built-in thermal disconnect, didn't they eliminate that from the plug? So maybe now it should just be called the "Plug".



If we are going to hate the NMEA 30A plug, let's hate it for valid reasons.



To me, the only thing a Smart Plug brings to the table is a functioning coupling/retention mechanism between the plug and receptacle. And it only brings that for the 30A plug. I don't think the 50A version is any better than the Hubbell 50A plug.

 

[rslifkin]

The L5-30 plug is mostly an issue due to it not being well retained. It's too easy to damage, so combined with the small contact area, it doesn't take much to cause a poor connection.

In addition, as much as some of you don't believe me, there's the 80% rule. Running an intermittent load (even for an hour) up to 100% is considered fine, but continuous loads shouldn't exceed 80% of the system rating (so 24A for a 30A line, 40A for a 50A line). Pushing 100% load for long periods of time will get a perfectly healthy system a bit warm, so it doesn't take much for that to change from warm to meltdown.

 

[oscar]

In addition, as much as some of you don't believe me, there's the 80% rule.

A good rule that applies to a lot of other things in life like lateral G's on two lane roads and trailer weights for instance.

The engineers design to 120% (give or take) which assumes everything being perfect. Staying a similar margin this side of 100% is just good practice.

The tendency to argue semantics on this forum, especially when it comes to safety issues is at the same time entertaining and disconcerting.

I'm sure someone will now explain that engineers design to 123%.....

 

[Comodave]

I'm curious who says the contacts are too small, other than Smart Plug? NEC and UL don't seem to think so. I don't doubt that the Smart Plug contacts are larger, but what's the basis for saying the NEC contacts are too small?


Now it may seem like I'm defending the 30A NMEA plug, and I'm not really trying to. I think it sucks, but more because it doesn't secure well enough for a marine application where constant movement can be expected. Those locking rings are a joke. I don't think I've ever been successful at getting two to mate together and do anything useful.



I'm just challenging the assertion that the contact area is "too small". Based on what?


And to Xsbank's point about the "Smart" in Smart Plug being a built-in thermal disconnect, didn't they eliminate that from the plug? So maybe now it should just be called the "Plug".



If we are going to hate the NMEA 30A plug, let's hate it for valid reasons.



To me, the only thing a Smart Plug brings to the table is a functioning coupling/retention mechanism between the plug and receptacle. And it only brings that for the 30A plug. I don't think the 50A version is any better than the Hubbell 50A plug.

Check marinehowto.com. He has an analysis of the L5-30 plug.

 

[twistedtree]

Check marinehowto.com. He has an analysis of the L5-30 plug.

I just read it over again. I still think the real issue is the poor coupling and support of the plug, not the contact surface area. Sure, more is good, but I really don't think that's the problem.


Just as a comparison, Rod showed 6.6 sq mm of contact area in the NMEA plug. AWG 10 wire is used in 30A cords, and the cross sectional area of #10 ga wire is 5.25. So the contact area, even in the worst case, exceeds the wire area.


Again, I really don't care for the 30A NMEA plug, and am using a Smart plug for the 30A service on my boat. But that's 100% because of coupling and support. For the 50A service I'm using the Hubbell 50A plugs.

 

[Xsbank]

I think you are all missing the point. Overloading is the problem, overload at your peril!

Think about this: You leave your boat in it's slip and the hot-water tank is on, the battery charger is on, your AIS and a couple of built-in USB plugs are running but not charging anything, then you need a heater in the engine room (many like to use block heaters) and maybe one in the saloon with all the cupboard doors open? Both heaters hit their trigger-points at the same time as the fridge kicks in, maybe the bilge pump burps the usual 1/2" of water out of the bilge and the battery charger kicks in...overload! 25 amps is very small. Now leave lights in the saloon, power a security system...? Now if you are sleeping onboard, you get up to pee, run some more lights then flush the toilet, wash your hands, the water pump comes on so you load the charger up more; plus you may have the heaters turned higher coz it's cold out there...

Comodave, why do you assume all boat wiring is up to the task? There are numerous threads on here about "do you believe what the p.o. did?"

To test your loading, put your meter in a wall socket. If you are one volt below the reading at the dock pedestal, you are overloading. While testing with the meter, turn on the microwave and wonder how it even turns on at <100 volts. Microwaves are very power hungry. What if you cook with an electric stove? Is the coffee sitting on the maker being kept warm?

Try it!

 

[Exctyengr]

This whole track has taken a turn towards the weeds. The OP's message is to simply check your shore power connection plugs for corrosion. Sounds to me like good advice and a practice that I use regularly. It really does not matter whether DC electrical causes more problems or not, the message is "check your AC plugs for corrosion"........(and let's all wear our masks"). Stay well everyone and this forum helps me stay sane during this covid thing.

 

[Comodave]

I just read it over again. I still think the real issue is the poor coupling and support of the plug, not the contact surface area. Sure, more is good, but I really don't think that's the problem.


Just as a comparison, Rod showed 6.6 sq mm of contact area in the NMEA plug. AWG 10 wire is used in 30A cords, and the cross sectional area of #10 ga wire is 5.25. So the contact area, even in the worst case, exceeds the wire area.


Again, I really don't care for the 30A NMEA plug, and am using a Smart plug for the 30A service on my boat. But that's 100% because of coupling and support. For the 50A service I'm using the Hubbell 50A plugs.

The contact area you are quoting is when conditions are perfect. Add even a bit of corrosion and the contact area gets smaller. That is why so many of them overheat. And they aren’t really a 30 amp conductor, more like 24 amps. We have had this on a previous boat that we owned, melted plug on the cable and on the boat. It had caused a fire inside the boat side of the plug but apparently the fire went out on it’s own probably due to lack of oxygen inside the small cabinet. If it had continued to burn the boat wouldn’t have been available for me to buy.

 

[Xsbank]

(Banging head on wall) I'm wasting my time again. Sorry to waste yours.

 

[NightCrawler]

Emory cloth the cord ends, rinse with an electrical spray cleaner and spray with T9. I even spray the dock receptical. Check the plugs with full heat pump, house loads with an IR gun. Then sleep well.

 

[Sailinggod]

Smart plugs not so smart

That is exactly why we went to Smart Plugs on our shore power cords.

Don’t assume Smart Plugs will prevent an overheated connection. I could show you a photo of my melted smart plug which appeared to have a loose connection on the inside (perhaps one of the screws became loosened) and it pretty much melted everything. Thank goodness my circuit breakers (and nose) detected the problem.
Make sure you check for heat as smart plugs won’t prevent overheating.
Cheers

 

[rbcooper]

Yup. The ONLY thing the smart plug supplies is greater surface area on the contacts. One must still remain vigilant on monitoring excess heat generated by poor or corroded contacts while running large electrical loads.

RB Cooper

 

[Comodave]

Don’t assume Smart Plugs will prevent an overheated connection. I could show you a photo of my melted smart plug which appeared to have a loose connection on the inside (perhaps one of the screws became loosened) and it pretty much melted everything. Thank goodness my circuit breakers (and nose) detected the problem.
Make sure you check for heat as smart plugs won’t prevent overheating.
Cheers

Anytime you have loose connections you stand the chance of heat buildup. Of course I meant but did not say that the connectors need to be tight. If you don’t maintain connections then all bets are off. But if you maintain the connections the Smart Plug is a superior product to the L5-30.

 

[Steve DAntonio]

Smart plug no longer includes a built in thermal overload, as that is considered an automatic resetting breaker of sorts, which is prohibited by ABYC Standards.

On the boat, you should not be able to "overload" a properly designed and maintained shore power system, if you do, a breaker should trip, and if it doesn't something is wrong. The user should not be the only thing preventing a fire from occurring. The dock, on the other hand, is an entirely different matter, as their receptacles and breakers are often in poor condition. The saving grace is, if dock components overheat, it rarely leads to a fire.

Having said that, I believe many onboard electrical fires occur because of marginal wiring that is overloaded with heating elements like space heaters. It works fine for years, until heavily loaded.

And, as far as the stats are concerned, it's extremely difficult to sift through the soggy, sooty remains of a boat fire to accurately determine the cause. Many boat fires' cause is never accurately determined.

It's important to remember that circuit breakers will not prevent high resistance overheating. That's explained in greater detail here https://stevedmarineconsulting.com/october-2011-newsletter/

 

[Helmsman]

Don’t assume Smart Plugs will prevent an overheated connection. I could show you a photo of my melted smart plug which appeared to have a loose connection on the inside (perhaps one of the screws became loosened) and it pretty much melted everything. Thank goodness my circuit breakers (and nose) detected the problem.
Make sure you check for heat as smart plugs won’t prevent overheating.
Cheers

I read a pretty good summary of best practices on installing the Smart Plug receptacle on the boat end a while back. I forgot where or I would post a link. The advice was to wait 5 hours or so after installation and check the tightening screws holding the AC wires. Check again in a couple of days. Once they stay tight they are ok. In many cases, the wires work loose after the initial tightening. Since mechanics and yards typically finish a job and move on this is rarely completed.

That may have been what happened to yours.m

 

[catalinajack]

In addition to the benefits of more pin contact area that a Smart Plug has, when plugging in it is so much easier. Push, click, done. With the standard plug, on my boat, it was always a struggle to get the locking blades lined up, then pushing and twisting, then engaging the locking ring all the while on my knees. Also, you get fa tory-made cordset rather than retrofitting an existing cordset you will no longer have to struggle with that stiff, heavy cord that was refitted. The Smart Plug cordset is lighter, coils easily, and does not get near-permanently solid with boat and dock grunge. Getting one has proven to be one of the wisest boat purchases I have made.

 

[Cartouche]

Helped a buddy move his boat today for haul out. He couldn't unplug one of the 30A shore power cords from the boat end, it was stuck. Several tools and a half hour later I had it all apart. It had gotten hot and plastic had melted and fused things together.

The wiring showed significant corrosion. So, that creates resistance which in turn causes heat, as well a voltage drop and then the amps go up to meet the wattage demand and keep the two A/C's (in his case) running.

He got close to a fire there. And, this is where a LOT if not most of the boat fires start.

So check those plugs and make sure they are not overheating!

As Commodore Dave Said exactly why we went to smart plugs, Old Marinco are lethal

 

[Comodave]

In addition to the benefits of more pin contact area that a Smart Plug has, when plugging in it is so much easier. Push, click, done. With the standard plug, on my boat, it was always a struggle to get the locking blades lined up, then pushing and twisting, then engaging the locking ring all the while on my knees. Also, you get fa tory-made cordset rather than retrofitting an existing cordset you will no longer have to struggle with that stiff, heavy cord that was refitted. The Smart Plug cordset is lighter, coils easily, and does not get near-permanently solid with boat and dock grunge. Getting one has proven to be one of the wisest boat purchases I have made.

I agree that the Smart Plug connectors are way easier to plug in than an L5-30. Unless we are docked starboard side to the dock, I have to get on my knees on the side deck, a bit narrow, to plug in the L5-30 connectors. With the Smart Plug I can do it just bending over and click it in and drop the cover and it latches onto the plug for extra security. Way easier and faster and much easier on my knees.

 

[Redhook98]

Another benefit of the Smartplugs is the wire is tinned throughout the entire cable. Marinco and others are not. Every single 30A Marinco, Camco, etc, I have torn apart have had un-tinned wiring. That alone is enough reason to switch over, IMO.

 

[psneeld]

Solved my accessibility issue and loosening issue as now the cord hangs straight down and weight is on the deck.

Anyone know if "marine grade" has to be tinned to be labeled that and UL (plus others) to be sold as that?

 

[727Gold]

Just to be clear: When taking on shore power start with shore breaker and boat breaker open, connect the shore power cable, shut the shore breaker, then shut the boat breaker. When taking off shore power, open both shore and boat breaker then disconnect the cable. Never connect/disconnect an energized cable. No sparks, no arcs. Learned this in USN 50 years ago - 450v/60hz/1200amp - lesson still applies to our "little" boats. Also, it pays to do a visual check of the plugs before connecting/energizing.

 

[Steve DAntonio]

I read a pretty good summary of best practices on installing the Smart Plug receptacle on the boat end a while back. I forgot where or I would post a link. The advice was to wait 5 hours or so after installation and check the tightening screws holding the AC wires. Check again in a couple of days. Once they stay tight they are ok. In many cases, the wires work loose after the initial tightening. Since mechanics and yards typically finish a job and move on this is rarely completed.

That may have been what happened to yours.m

As much as I like the SmartPlug product, I recommend it for my clients, I don't care for their rotating screw tip design to get around the ABYC 'no direct bearing screws' requirement. It's clearly passed all the tests so it works, I just would prefer to see a floor plate design instead.

I am aware of two overheats (not fires) in SmartPlugs, one of which I repaired myself, both of which SP warrantied. Therefore, these plugs should still be inspected for signs of overheating at the pin to insulator interface, every time they are used, which can be caused by among other things a loose screw to conductor connection.

The other small nit I have with them is I encounter many boat inlet back ends that are not insulated, and have exposed, energized screw heads. If you are installing one, remember the back side needs to be covered.

Again, I like the product very much, it's light years ahead of the legacy NEMA system.

 

[Capt. Carman]

Amen !!!! Smart Plug is the way to go !

 

[ghost]

I’ve got an early model melted smartplug. Actually, I was able to,put it back together with a different and newer cord set and have it as a backup somewhere. One of my early adopter friends had the same issue. Neither of us had success with the thermal fuse, they just kept on heating. I’ve stood and talked with the Smartplug guys in their office, great great group of people, but they were really resistant early on that people were simply putting them together wrong. Maybe, maybe not, but that thermal breaker was surely not calibrated very well.

I tend to recommend getting the entire new cordset, already molded to the cord, as just attaching to a corroded Marinco cord was not foolproof. My old orange smartplug cord is now getting quite long in the tooth. I should probably replace it, but even after ten+ years it is not heating up, I check it with the infrared camera every year.

I’d happily upgrade to a 50 amp, but my marina only has 30 amp and we are not upgrading anytime soon.

 

[Ruffryder]

Smart plug can burn/melt down too... I've seen enough cases. Maybe these pics were floating around here...

NEC only limits 80% load of over current devices, that's 24 amp on a 30 amp shore power breaker, 40 on 50 amp.

 

[FF]

Yup. "
The ONLY thing the smart plug supplies is greater surface area on the contacts."

For those that wish to be safer the std home range plug is rated 240v 50a per leg , and is easy to assemble and perhaps 1/10 the cost of a smart plug.

They have been used in the RV industry for many decades and the newer plugs have a handle to unplug easily .

Here is one ,

https://www.walmart.com/ip/Camco-55.../29764608?wmlspartner=wlpa&selectedSellerId=0

 

[oscar]

Yup. "
The ONLY thing the smart plug supplies is greater surface area on the contacts."

For those that wish to be safer the std home range plug is rated 240v 50a per leg , and is easy to assemble and perhaps 1/10 the cost of a smart plug.

They have been used in the RV industry for many decades and the newer plugs have a handle to unplug easily .

Here is one ,

https://www.walmart.com/ip/Camco-55.../29764608?wmlspartner=wlpa&selectedSellerId=0

Hmmm, not aware of a water proof connector to build into the deck. On my moho the connection is inside a cabinet out of the weather. So maybe in a lazarette or the anchor locker but not on deck.

 

[Ruffryder]

For those have a Facebook account, notice where this fire started from...
https://m.facebook.com/groups/176379089768136?view=permalink&id=722684728470900

 

[ghost]

It looks like it started from the old corroded yellow cheapo Marinco cord that should have been replaced instead of reused.

Okay, I can’t quite see that clearly, but having made that mistake, I admit to a strong bias that was the root of the problem.

 

[BDofMSP]

Yup. The ONLY thing the smart plug supplies is greater surface area on the contacts. One must still remain vigilant on monitoring excess heat generated by poor or corroded contacts while running large electrical loads.

Not the ONLY. It also provides far superior locking and strain relief compared to a standard 30 amp. That is what drove me to install one on my last boat and I loved it.

Now I have a Glendinning on 50 amp so there is no boat side connector to worry about.

BD