Smart Plugs - Still A Good Solution or No Longer In Vogue?

[scooper321]

I posted this over in the 400DB forum but wanted to get a broader audience and comments.

Looking for experience on people that have replaced their Marinco shore power threaded inlets with Smart Plug inlets. I haven't seen any discussion about Smart Plug in this forum (Electronics) since middle of last year, so I'm wondering is the Smart Plug still a good option or is it now yesterday's news? I know it's been around for about 15 years or more, but doesn't seem to be getting more than cult following.

A recent insurance survey showed the very beginnings of some discoloration on one of the boat’s shoe power inlets. I’m not fooling around with this and so I'm looking to replace the inlet. Probably both of them (my boat has two 30A inlets).

The easiest soution would be to put new Marinco stainless inlets in. The inlets that are there are the white plastic ones and they are 20+ years old. So, not too shabby. Replacing them with new Marinco ones should get me 20 more years, right? So ... do I need to go to Smart Plug? I do inspect my power connections, so I'm wondering if it's overkill for a boater like me?

Sticking with Marinco, besides the inlets the only other expense would be new shore power cords for my home dock. My travel cords are relatively new and in good shape. So, all told, tis approach comes to about $200 per port. I could save a couple bucks by replacing just the power cord female connectors. I currently have the EEL connectors on there and I can’t seem to find them connectors on line anywhere. Does Marinco not sell them stand-alone for retrofit applications? If not, re-connectorizing my cord would mean using the locking ring style connectors. Some think that's more reliable than the EEL mechanism anyway. I’ve had both and never had an issue with the thread-on rings. The price difference is negligle in boat terms.

The big advantage of doing a Marinco replacement is that it's cheap, and I don’t need to modify or replace travel cords.

Smart Plug is a bit more expensive. Not just the components, but switching connection "ecosystems" means a bit more out of pocket. Switching to Smart Plug would require not only new inlets on the boat, but 4 new connectors that I would retrofit on both my home and travel shore power cord sets. This comes in at just under $400 per port. I could drive the cost even higher by buying completely new orange home dock SP cords. I'd still retrofit SP connectors on my travel cords.

I'm curious how secure the Smart Plug connection mechanism is... not just on Day 1 but after 5 years, 10 years? Does it hold the connections secure? Loose connections is THE main reason for charred inlets and connectors (and boat fires at the inlets). To my mind, the threaded connection seems to be the most secure option, but I like the larger contacts of the Smart Plug for minimal resistance.

I guess what I'm asking is ... who has the Smart Plug? How long have you had it and are you still happy with it? Did you find it to be worth the money? Yes, I know "it's worth it to prevent a fire". But if quality installation of the new Marinco parts and regular inspection of the connections will also prevent a fire, does the SP buy us anything additional? Is there any reason - other than cost - NOT to switch to Smart Plug?

Thanks,
Steve

 

[Skybolt]

@scooper321 Steve, No real experience with Smart plug, but just my two cents.

I don't see the value of switching to a proprietary power system like this. If you concerned with the connectors why not switch over to 50A. They are much more heavy duty and have a better securing mechanism.

My boat came from the factory with 50A Marinco connection. The PO switched over to twin 30's and relocated them to the stern, after some use by me, I realized it needed to go back to 50A. Right about that time the Smart plug was introduced at a boat show. The cost was a bit high to say the least and I didn't see the benefit over the standard 50A Marinco setup.

So I opted to stay with Marinco. Moving to the 50A setup resolved all worry about burning out connectors and the like. The 50A connector and cord set are very strong and do not move about like the 30's do. Take that as food for thought.

 

[Irie308]

I kept burning my plugs and the receptacles at the boat. Replaced 3 times in 5 years. Was told it was power at my marina. Moved to a diff marina and had same issue.Went to the smart plug last spring and no more burnt plugs. I normally would see charring after 1 season. I also think they fit more securely than the threaded ones. Only regret is not doing it sooner. I do travel with them as it’s easier to remove from my pedestal rather than from my transom.

 

[bfernald0]

I posted this over in the 400DB forum but wanted to get a broader audience and comments.

Looking for experience on people that have replaced their Marinco shore power threaded inlets with Smart Plug inlets. I haven't seen any discussion about Smart Plug in this forum (Electronics) since middle of last year, so I'm wondering is the Smart Plug still a good option or is it now yesterday's news? I know it's been around for about 15 years or more, but doesn't seem to be getting more than cult following.

A recent insurance survey showed the very beginnings of some discoloration on one of the boat’s shoe power inlets. I’m not fooling around with this and so I'm looking to replace the inlet. Probably both of them (my boat has two 30A inlets).

The easiest soution would be to put new Marinco stainless inlets in. The inlets that are there are the white plastic ones and they are 20+ years old. So, not too shabby. Replacing them with new Marinco ones should get me 20 more years, right? So ... do I need to go to Smart Plug? I do inspect my power connections, so I'm wondering if it's overkill for a boater like me?

Sticking with Marinco, besides the inlets the only other expense would be new shore power cords for my home dock. My travel cords are relatively new and in good shape. So, all told, tis approach comes to about $200 per port. I could save a couple bucks by replacing just the power cord female connectors. I currently have the EEL connectors on there and I can’t seem to find them connectors on line anywhere. Does Marinco not sell them stand-alone for retrofit applications? If not, re-connectorizing my cord would mean using the locking ring style connectors. Some think that's more reliable than the EEL mechanism anyway. I’ve had both and never had an issue with the thread-on rings. The price difference is negligle in boat terms.

The big advantage of doing a Marinco replacement is that it's cheap, and I don’t need to modify or replace travel cords.

Smart Plug is a bit more expensive. Not just the components, but switching connection "ecosystems" means a bit more out of pocket. Switching to Smart Plug would require not only new inlets on the boat, but 4 new connectors that I would retrofit on both my home and travel shore power cord sets. This comes in at just under $400 per port. I could drive the cost even higher by buying completely new orange home dock SP cords. I'd still retrofit SP connectors on my travel cords.

I'm curious how secure the Smart Plug connection mechanism is... not just on Day 1 but after 5 years, 10 years? Does it hold the connections secure? Loose connections is THE main reason for charred inlets and connectors (and boat fires at the inlets). To my mind, the threaded connection seems to be the most secure option, but I like the larger contacts of the Smart Plug for minimal resistance.

I guess what I'm asking is ... who has the Smart Plug? How long have you had it and are you still happy with it? Did you find it to be worth the money? Yes, I know "it's worth it to prevent a fire". But if quality installation of the new Marinco parts and regular inspection of the connections will also prevent a fire, does the SP buy us anything additional? Is there any reason - other than cost - NOT to switch to Smart Plug?

Thanks,
Steve

Converted my existing Marinco shore power cord to the smart plug setup on the boat side a few years ago. The kit was a direct swap in terms of the boat side receptacle (no additional drilling, etc.), and was an easy wiring job on the shore power cord. Would never go back. Plug does not come undone, no more melted plugs, and the other end remains fully compatible with the standard set up at most marinas.

 

[scooper321]

@scooper321 Steve, No real experience with Smart plug, but just my two cents.

I don't see the value of switching to a proprietary power system like this. If you concerned with the connectors why not switch over to 50A. They are much more heavy duty and have a better securing mechanism.

My boat came from the factory with 50A Marinco connection. The PO switched over to twin 30's and relocated them to the stern, after some use by me, I realized it needed to go back to 50A. Right about that time the Smart plug was introduced at a boat show. The cost was a bit high to say the least and I didn't see the benefit over the standard 50A Marinco setup.

So I opted to stay with Marinco. Moving to the 50A setup resolved all worry about burning out connectors and the like. The 50A connector and cord set are very strong and do not move about like the 30's do. Take that as food for thought.

Fair point about the 50A Marinco being more stable (and using larger contacts) than the 30A. But swtiching a dual-30A boat over to a single 50A is a non-starter. Switching to a single 50A would require far too much electrical work inside the boat. Plus, I'd be giving up 10A. So that's not feasbile.

If I switch to Smart Plug, I replace 4 connectors. If I stay with Marinco I replace my 2 shore power cords. Marinco don't seem to sell the EEL connectors as replaceable items.

 

[John E3]

I went through a similar situation and talked with my well experienced emergency generator nephew (mostly commercial), as I could not find a straight answer to 50a vs 30a, after extensive research.
He was awoken (onboard) by a neighbor last year at 6am due to smoke at his cord inlets. One of the marinco 30a twistlocks was seconds from fire. He switched to Smartplug the next day.
I checked my cords (first season for us with this boat), and L1 was burned black on the hot wire, and brown on neutral. L2 had a small discoloration. I replaced both inlets and cord ends and bought the smart plug setup for future install. I am not a professional electrician, but I have 50+ years experience in related fields, and still frustrated with what I found.

The questions I had that I could not find a straight answer to on the Smart Plug, or 50A shore power in general.
Is the 50A rating PER Leg or combined?
Are the 2 legs the same line, ie 0v between them, or 240v between?

My nephew also was not sure, but raised the following point:

If the 2 legs are the same Line from the source, then no 1 wire (including neutral) CAN carry more than 50A, which means you get 50a TOTAL. This is 10 less than 2 x 30A. This doesn't seem correct. To carry 50 on both would be 100 on the neutral.

If the 2 legs are split lines (ie 240 between them), then you get a full 50A on BOTH, and neutral carries anywhere from 0 to 50 depending on load distribution.

If you look at the description of the standard 50A cord it says 125/250, so the the latter above appears to be the correct answer, but I'd love to see the specs clearly defined. I didn't think to put a meter on the 2 lines and see, but I have little doubt.

The standard 50 may feel more secure, but no more so than a 30 with the locking ring secured. They are still small twist lock pins, and there is no locking ring on the dock end for 50A at our marina. Those twist lock pins would then be carrying up to 50A each. That makes me uncomfortable after having found burned 30A pins.

I removed the TV/phone inlet and the smartplug connector was a drop in fit. I searched everywhere for a 50A breaker, and came up empty, as I was going to run a new 50A wire to the panel. Given that the panel has 30A breakers, a new wire is kind of pointless as it would never exceed 30A anyway. Instead I will just connect the Smartplug inlet to the 30A inlet breakers. We've have to turn on every 120v device onboard, at the same time, to even get to 2x30, so nothing lost in the end. I did add up everything when researching used genset options as our 9.6 (80A) had a blown engine when we got it, and the best I could find used was a 7.0. I don't recall the total, but decided the 7.0 (58A) was enough as it pretty much equally the 2x30A inlets. I've since learned it was an option in our boat originally.

Even if you switch to 50, you will still be limited by the boat wiring and panel breakers, to 30A.

 

[scooper321]

I went through a similar situation and talked with my well experienced emergency generator nephew (mostly commercial), as I could not find a straight answer to 50a vs 30a, after extensive research.
He was awoken (onboard) by a neighbor last year at 6am due to smoke at his cord inlets. One of the marinco 30a twistlocks was seconds from fire. He switched to Smartplug the next day.
I checked my cords (first season for us with this boat), and L1 was burned black on the hot wire, and brown on neutral. L2 had a small discoloration. I replaced both inlets and cord ends and bought the smart plug setup for future install. I am not a professional electrician, but I have 50+ years experience in related fields, and still frustrated with what I found.

The questions I had that I could not find a straight answer to on the Smart Plug, or 50A shore power in general.
Is the 50A rating PER Leg or combined?
Are the 2 legs the same line, ie 0v between them, or 240v between?

My nephew also was not sure, but raised the following point:

If the 2 legs are the same Line from the source, then no 1 wire (including neutral) CAN carry more than 50A, which means you get 50a TOTAL. This is 10 less than 2 x 30A. This doesn't seem correct. To carry 50 on both would be 100 on the neutral.

If the 2 legs are split lines (ie 240 between them), then you get a full 50A on BOTH, and neutral carries anywhere from 0 to 50 depending on load distribution.

If you look at the description of the standard 50A cord it says 125/250, so the the latter above appears to be the correct answer, but I'd love to see the specs clearly defined. I didn't think to put a meter on the 2 lines and see, but I have little doubt.

The standard 50 may feel more secure, but no more so than a 30 with the locking ring secured. They are still small twist lock pins, and there is no locking ring on the dock end for 50A at our marina. Those twist lock pins would then be carrying up to 50A each. That makes me uncomfortable after having found burned 30A pins.

I removed the TV/phone inlet and the smartplug connector was a drop in fit. I searched everywhere for a 50A breaker, and came up empty, as I was going to run a new 50A wire to the panel. Given that the panel has 30A breakers, a new wire is kind of pointless as it would never exceed 30A anyway. Instead I will just connect the Smartplug inlet to the 30A inlet breakers. We've have to turn on every 120v device onboard, at the same time, to even get to 2x30, so nothing lost in the end. I did add up everything when researching used genset options as our 9.6 (80A) had a blown engine when we got it, and the best I could find used was a 7.0. I don't recall the total, but decided the 7.0 (58A) was enough as it pretty much equally the 2x30A inlets. I've since learned it was an option in our boat originally.

Even if you switch to 50, you will still be limited by the boat wiring and panel breakers, to 30A.

The 50A connectors are 50A combined. At least in the US it is. When we travel we commonly dock in a slip that has a 50A (120V) dock pedetal. We then use a splitter to produce our dual 30A connections. Yep, that's going to be a problem if we ever draw 30A on each of them. But that's how the boating world works. I haven't ever had a problem. We don't draw anywhere close to that. So yes, the 50A is TOTAL of 50A and yes, you're giving up 10A vs. dual 30s.

Also, this is 120VAC circutry, not 240VAC. I suppose those connectors might be able to support 240V - but few boats in the states are 240V, so I've never looked. For the purpose of this discussion ther recommendation was 50A at 120VAC. But, as you noted, my boat's wiring and breakers make bringing in a single 50A a messy retrofit, so that's not feasible.

Lots of scary stories like this about the Marinco inlets. It's clear they are suspect, if they are left alone and not inspected or serviced. I can't imagine ever going to plug in a shore power connector to my boat, seeing anything brown (or black!) and ignoring it. I look at the plug contacts and the female connector sockets regularly. In fact, this whole discussion arose because there's a teeny bit of browning starting on one of the contacts on one of my inlets. It's very, very little. But I'm taking it seriously.

In all these inlet fire stories it seems like the common thread is the boat owners no inspecting their electrical inlets often (or at all). So perhaps it's not the technology but the boat owner that is the weak point? That being said, no one is perfect and stuff happens. And sometimes it's NOT the boat owner's negligence. How often that siuation occurs is what I'm trying to understand.

 

[John E3]

Also, this is 120VAC circutry, not 240VAC. I suppose those connectors might be able to support 240V - but few boats in the states are 240V, so I've never looked. For the purpose of this discussion ther recommendation was 50A at 120VAC. But, as you noted, my boat's wiring and breakers make bringing in a single 50A a messy retrofit, so that's not feasible.

You do realize that the 50A cord has 2 hot lines, 1 neutral and 1 ground, right? They are designated 120/240, so there'd better be 240 between the 2 hot legs, or that designation is wrong. And 120v from either hot to neutral of course. No different from house wiring.

If the 2 lines are on the same hot leg from the dock power, than the neutral leg will carry the SUM of the current from those 2 lines, or 100A when fully loaded. That will probably melt the neutral insulation. This is clearly not how it works.

If they are split lines from the dock power, ie 240 between them, neutral will only carry the DIFFERENCE of the 2 lines, a max of 50A. And can supply 240V if the other end (aka a boat) needs it.

Dual 30A/125V cords could be either way, a common 120V line or 240V between the 2 cords hot wires, it just depends on which receptacle you plug into, as the dock wiring would have 1/2 the 120V receptacles on 1 line and the other 1/2 on the other line. And each has it's own neutral. It makes no difference to the boat.

It's simple AC power distribution. How it's connected inside the panel makes a difference. My manual has 120v and 220v wiring diagrams, and even the 220v (non-US power is 220) has 2 isolated circuits, and the breakers are 16A as you only need half the current with double the voltage.

My 370AC has nothing connected between the 2 30A circuits, so it's a 120v system, as all the rest of the US market ones would be. Other brands that have only a 50A inlet could use 240v appliances, and I suspect they would be bigger, and have bigger needs. Some even have dual 50'a.

The Genset is 120V, and has the 2 legs connected in it's control by a buss bar on the genset side of it's breaker. The lockout in the panel for Gen/Shore prevents any cross connections. The non-US have a 220V genset.

Bring in the 50, connect it to a 30A breaker and you still have the same as 2x30, but you can't use the extra 40A that's available. The panel is the limiting factor.

 

[scooper321]

You do realize that the 50A cord has 2 hot lines, 1 neutral and 1 ground, right? They are designated 120/240, so there'd better be 240 between the 2 hot legs, or that designation is wrong. And 120v from either hot to neutral of course. No different from house wiring.

If the 2 lines are on the same hot leg from the dock power, than the neutral leg will carry the SUM of the current from those 2 lines, or 100A when fully loaded. That will probably melt the neutral insulation. This is clearly not how it works.

If they are split lines from the dock power, ie 240 between them, neutral will only carry the DIFFERENCE of the 2 lines, a max of 50A. And can supply 240V if the other end (aka a boat) needs it.

Dual 30A/125V cords could be either way, a common 120V line or 240V between the 2 cords hot wires, it just depends on which receptacle you plug into, as the dock wiring would have 1/2 the 120V receptacles on 1 line and the other 1/2 on the other line. And each has it's own neutral. It makes no difference to the boat.

It's simple AC power distribution. How it's connected inside the panel makes a difference. My manual has 120v and 220v wiring diagrams, and even the 220v (non-US power is 220) has 2 isolated circuits, and the breakers are 16A as you only need half the current with double the voltage.

My 370AC has nothing connected between the 2 30A circuits, so it's a 120v system, as all the rest of the US market ones would be. Other brands that have only a 50A inlet could use 240v appliances, and I suspect they would be bigger, and have bigger needs. Some even have dual 50'a.

The Genset is 120V, and has the 2 legs connected in it's control by a buss bar on the genset side of it's breaker. The lockout in the panel for Gen/Shore prevents any cross connections. The non-US have a 220V genset.

Bring in the 50, connect it to a 30A breaker and you still have the same as 2x30, but you can't use the extra 40A that's available. The panel is the limiting factor.

I do realize that's how it works. That's why I made a point of saying 50A TOTAL. It sounds like you already knew this so I'm not sure what you were asking in your prior post. And as I mentioned, I can't comment on how the 240V is handled - especially not at the dock pedetsal. Sounds like you already know how that's wired, though. Thanks for the tutorial!

 

[John E3]

I do realize that's how it works. That's why I made a point of saying 50A TOTAL. It sounds like you already knew this so I'm not sure what you were asking in your prior post. And as I mentioned, I can't comment on how the 240V is handled - especially not at the dock pedetsal. Sounds like you already know how that's wired, though. Thanks for the tutorial!

Actually I better understood it as I was describing it.
It is 50A PER LEG. They do not clearly state this anywhere that I can find on their website, but the below infers it. Same cord, same boat ends. Different dock ends to meet different dock connectors.

50A @ 240V = 2 x 50A @120V. Both legs can carry 50 amps regardless of how you connect/use the boat end.
Using Ohms Law:
50Ax240v=12,000 watts, 50A per hot wire
12,000w/120v=100Amps, also 50A per hot wire

 

[dtfeld]

I've looked at this as part of moving from the 2x30 to a 50A shore power setup. The SmartPlug seems to be a better mouse trap and for 2x30A setups I think they are superior, there is more metal and more contact area, so less resistance and heat.

I haven't done a deep dive on the 50A versions yet, but one consideration for me is that I believe I can swap out the existing Marinco 30A plug and replace with a 50A version in the same body/mount on the boat. This very much simplifies the project...no holes to be cut.

One this to consider is the total power available from a 2x30A vs a 50A 120/240 system. Each 30A system at 120VAC give you 3600W of power, so for 2x30A we have 7200W total. The 50A 120/240 is 2 legs @50A each for a total of 12000W.

It also matters how the dock is wired as to how much power you can get.

If using a smart Y to connect 2x30A --> 50A, the legs need to be 180* out of phase (just like a house). This is basically 30A 120/240. If the 2 are wired off the same get (in phase) you cant use a smart Y. But you can still get 2X30A to work.

Shore power designations in the US suck...

 

[John E3]

I haven't done a deep dive on the 50A versions yet, but one consideration for me is that I believe I can swap out the existing Marinco 30A plug and replace with a 50A version in the same body/mount on the boat. This very much simplifies the project...no holes to be cut.

It also atters how the dock is wired...

Yes, they drop in, same exact hole pattern. I removed my TV/phone jack to install mine.

I alluded to the dock wiring point. Every 30A/120 down the dock could be on Line1, or Line2 or an equal mix of both (as it probably is or their electrician should be keel hauled) and the boat won't know, or care, which 2 you use.
The 50-120/240 -must- have both 1 & 2 or there is no 240 and you risk overloading neutral as I described earlier.

I'll bet you can't buy a dual 30 TO 50 "combiner" (opposite of 50 to dual 30 splitter) as this could lead to an overloaded neutral if both 30's are on the same line.

 

[dtfeld]

Yes, they drop in, same exact hole pattern. I removed my TV/phone jack to install mine.

I alluded to the dock wiring point. Every 30A/120 down the dock could be on Line1, or Line2 or an equal mix of both (as it probably is or their electrician should be keel hauled) and the boat won't know, or care, which 2 you use.
The 50-120/240 -must- have both 1 & 2 or there is no 240 and you risk overloading neutral as I described earlier.

I'll bet you can't buy a dual 30 TO 50 "combiner" (opposite of 50 to dual 30 splitter) as this could lead to an overloaded neutral if both 30's are on the same line.

Good info on the same hole pattern.

I agree dual 30A's should be a combo L1/L2. Otherwise they are of little use to a 50A boat trying to get at least some marginal power.

The Smart Y's have built in logic that will only connect if you have 30A "split phase" for lack of a better term. Both on the same leg=no power.

 

[Skybolt]

Fair point about the 50A Marinco being more stable (and using larger contacts) than the 30A. But swtiching a dual-30A boat over to a single 50A is a non-starter. Switching to a single 50A would require far too much electrical work inside the boat. Plus, I'd be giving up 10A. So that's not feasbile.

If I switch to Smart Plug, I replace 4 connectors. If I stay with Marinco I replace my 2 shore power cords. Marinco don't seem to sell the EEL connectors as replaceable items.

I get the work involved with converting to 50A. But you would be gaining amperage, not giving up any. A 50A supply is two legs of 120v @50A. So you would be gaining 20A per each leg in supply current.

 

[SeasNT]

I get the work involved with converting to 50A. But you would be gaining amperage, not giving up any. A 50A supply is two legs of 120v @50A. So you would be gaining 20A per each leg in supply current.

That's why those 50 amp cables are so darn heavy. Two 30's are pretty easy to handle.