Stateroom Fires caused by Surge Protectors

The U.S. Coast Guard has issued a Marine Safety Alert regarding the risk of fire from Surge Protective Devices sometimes called power strips. The link is here Surge Protective Devices Aboard Vessels. (pdf file)

Our company implemented this notice via a safety alert and inspection of household type surge protectors in use onboard showed burned components inside. So it appears to be a very real concern. Initial shopping around for “correct” type shows they are about $90.00 each. It is not a matter of overloading an individual strip but that only one side of the circuit is opened on a fault. One of those ounce of prevention worth a pound of cure deals. If you must have surge protection, worth getting the right device.

One of the biggest pain in the ass that I had to deal with was having crew members plug way too much stuff into on outlet. I remember one guy had three of those Power Strips plugged into each other and could not understand what my problem with him was. I guess tripping a breaker every time he was off watch was just me picking on him.

Hopefully, this will wake up everyone about the Dangers that come with these “Cheap” Power Strips.

[QUOTE=“KPChief;114672”]Our company implemented this notice via a safety alert and inspection of household type surge protectors in use onboard showed burned components inside. So it appears to be a very real concern. Initial shopping around for “correct” type shows they are about $90.00 each. It is not a matter of overloading an individual strip but that only one side of the circuit is opened on a fault. One of those ounce of prevention worth a pound of cure deals. If you must have surge protection, worth getting the right device.[/QUOTE]

You only need the “right” surge protector if your boat is wired a certain way. We had our engineers verify the boat was wired the correct way at every outlet then there is nothing to worry about.

I read the safety bulletin. Why would anyone wire a system so that ground was 60 volts from neutral? How is this wired? Did they run 240 into a 2:1 step down transformer and look at the lead for the center tap a say what do I do with this? “I don’t know, hook it to the green wire.” The uscg makes it sound like this grounding system is common practice. If this wasn’t just bad wiring, does anyone know why you would want your ground 60 volts from neutral and where ground is tied into the system to achieve this?

[QUOTE=Shadow;114675]I read the safety bulletin. Why would anyone wire a system so that ground was 60 volts from neutral? How is this wired? Did they run 240 into a 2:1 step down transformer and look at the lead for the center tap a say what do I do with this? “I don’t know, hook it to the green wire.” The uscg makes it sound like this grounding system is common practice. If this wasn’t just bad wiring, does anyone know why you would want your ground 60 volts from neutral and where ground is tied into the system to achieve this?[/QUOTE]

The reason this caught my eye is because we had an issue not with the power strip but with the bigger UPS which is also mentioned.

I wasn’t aboard at the time but one overheated and had to be disconnected and taken out on deck. I don’ t think anyone fully understood what the issue was, other equipment had issues as well and some failed but the UPS was the only one that cooked.

My understanding was a barrier between systems was bypassed at some point and later a second separate issue caused some kind of weird electrical seiche.

[QUOTE=Shadow;114675]I read the safety bulletin. Why would anyone wire a system so that ground was 60 volts from neutral? How is this wired? Did they run 240 into a 2:1 step down transformer and look at the lead for the center tap a say what do I do with this? “I don’t know, hook it to the green wire.” The uscg makes it sound like this grounding system is common practice. If this wasn’t just bad wiring, does anyone know why you would want your ground 60 volts from neutral and where ground is tied into the system to achieve this?[/QUOTE]

Every U.S. built vessel I’ve sailed had wye configuration on the lighting branch. Some foreign built vessels I’ve sailed were 220 to 250 on the lighting branch in delta. We used single phase utility transformers for U.S. appliances. I can see where this could morph into a problem with the power strips.

I have been on a salvage job where skid mounted gensets were in delta with a tap on one winding for 120vac aux equipment.

[QUOTE=Shadow;114675]I read the safety bulletin. Why would anyone wire a system so that ground was 60 volts from neutral?[/QUOTE]

Because the ship’s hull is not meant to be a power conductor. The safety ground (the round bit on the socket) goes to the hull but the neutral is not connected to the hull since the hull is not supposed to be a conductor.

If you measure between the two flat bits, you get 120 volts, if you measure between either one and the safety ground you will get 60 volts. This is intended to allow continued delivery of power in the event one conductor is grounded. It also protects sailors who might contact a power conductor, they will only get zapped by half the voltage. In a 3 phase generation and distribution system this allows a partial ground to exist without shutting down the whole system. It also means that a second unrelated ground on another phase can be catastrophic.

Those cheap surge protectors only open one side of the circuit which is OK in a household system but on a Delta fed lighting circuit it means the full fault current can flow through the other conductor and start a fire.

[QUOTE=Shadow;114675] Why would anyone wire a system so that ground was 60 volts from neutral? [/QUOTE] Acceptable voltage for any 120 volt appliance is zero volts (neutral to safety ground), 60 volts, and 120 volts (neutral to safety ground). That becomes obvious by learning how appliances (especially electronics) are designed. A design requirement each is required to meet.

No surge protector works by disconnecting one lead (wire). First function: power strips disconnect only a hot wire when appliances demand too much power from that strip. An anomaly that is completely different from what the other function addresses - surge protection.

That first function does not cause power strip fires. The second function sometimes does.

[QUOTE=westom;114746]Acceptable voltage for any 120 volt appliance is zero volts (neutral to safety ground), 60 volts, and 120 volts (neutral to safety ground). That becomes obvious by learning how appliances (especially electronics) are designed.[/QUOTE]

We are not talking about house electrical systems …

That first function does not cause power strip fires …

I think there are a bunch of folks in the marine casualty investigation business who would disagree.

[QUOTE=Steamer;114749]We are not talking about house electrical systems …[/QUOTE] That is correct. We are talking about all electrical systems that all 120 volt appliances operate safely on. And about a post that said, “Why would anyone wire a system so that ground was 60 volts from neutral?”

If you know something different, then also say why. Denials without the reasons why (and numbers) contribute nothing useful.

If you know a power strip (without surge protector functions) causes a fire, then also say why. Otherwise it is an empty denial.

Obviously, daisy chaining power strips is a human safety threat in all environments: commercial, home or marine. Nobody is saying anything different. If a properly connected power strip can cause fires, then also say why (with numbers).

[QUOTE=“westom;114750”] That is correct. We are talking about all electrical systems that all 120 volt appliances operate safely on. And about a post that said, “Why would anyone wire a system so that ground was 60 volts from neutral?”

If you know something different, then also say why. Denials without the reasons why (and numbers) contribute nothing useful.

If you know a power strip (without surge protector functions) causes a fire, then also say why. Otherwise it is an empty denial.

Obviously, daisy chaining power strips is a human safety threat in all environments: commercial, home or marine. Nobody is saying anything different. If a properly connected power strip can cause fires, then also say why (with numbers).[/QUOTE]

Did you read the safety bulletin before acting like you know what you are talking about?

Steamer’s explanation makes sense to me. If my understanding is correct household wiring uses hot wire to neutral wire for 120 volts and 120 hot to 120 hot, 180 degrees out of phase for 240 volts. Shipboard the Delta configuration uses two 60 volt out of phase for 120 volts same way two 120 wires make 240 in a house.

Some surge protectors are designed assuming one hot and one neutral but shipboard the wiring in delta is both hot.

So, it seems obvious that this grounding system is pretty common. I’ve never seen it, but I’ve never worked on a large ship, just tugs, small passenger vessels, and fishing boats. Could some one explain where you would tie this ground in to get it 60 volts from neutral. Also, it seems to me that this type of system would really limit the type of equipment you could use on it. For instance if you used a standard square d panel, half of your 120 volt circuits would have ground 60 volts from neutral and hot, but the other half would be 180 volts from hot and ground.

April 08, 2013 Washington, DC
03-13
Inspections and Compliance Directorate
Surge Protective Devices Onboard Vessels
We’ve all seen them and used them. Surge protective devices (SPDs), more commonly known as surge protectors or power strips help protect our expensive electronic devices from being damaged from excessive currents and allow us to deliver power to multiple devices simultaneously. This safety alert addresses the use of certain electrical protection devices onboard vessels and the inherent risks they may cause. Most commercially available SPDs are designed for use ashore and will interrupt only the hot conductor when a surge occurs. What does that mean for the ship owner/operator? It means that while these devices may provide protection in our homes and offices, these same devices may be a fire risk onboard vessels.
A marine casualty investigation of two separate
stateroom fires onboard a U.S. Flag Container
ship revealed that the sources of the fires were
attributed to the use of SPDs plugged into a
lighting circuit. It was discovered that a ground
had developed on another circuit that was
connected to the same distribution panel
providing power to the staterooms. This ground
created an imbalance of voltage between the
two power conductors supplying the SPDs
which caused excessive currents, overheating,
and subsequently, a fire. In this instance, even
if the SPDs automatically tripped as designed,
only one power conductor would have been
secured while the other would continue to
provide power, possibly shorting to the device’s ground wire and the structure of the vessel.
For shipboard applications, it is critical for a device to interrupt both power conductors. Underwriters Lab Standard - UL Marine 1449 – addresses this issue and applies to the use of SPDs.
The Coast Guard recommends that vessel Owners, Operators, Class Society Surveyors, Insurers, and other inspection personnel examine the risks associated with the use of SPDs aboard their vessels, and if necessary ensure their organizations have policies and procedures relating to their use. Vessels should have defined procedures for checking the condition and grounding capabilities of personal/portable electrical equipment, and trained shipboard personnel should be assigned to check and approve all SPDs in use or brought on board for compatibility with the vessel’s electrical distribution system prior to use. Routine checks of switchboard and distribution system 120 VAC ground detection systems are necessary to detect the presence of grounds that may cause similar circumstances with non-marine type SPDs. These recommendations are not mandated rather just an advisory based on lessons learned from the casualty.

So, uh, delta 120 has two hots… How does ground fault on adjacent circuit burn up surge gizmo’s? Opening one leg should be enough… Aww Shit, I gotta think…

Now I got a headache…

Got it, maybe… Gizmo senses imbalance between hot/hot, opens what it thinks is hot, and closes to what it thinks is neutral, which is also hot?

Maybe the 3rd party riggers should NOT plug and charge their 3 cell phones into a power strip. OH, they got to get their chat/surf/text/mail/music and ALL downloads on…Sorry, I forgot
Morons with more than 2 cell phones and a tablet/pc…

[QUOTE=Shadow;114762]So, it seems obvious that this grounding system is pretty common. I’ve never seen it, but I’ve never worked on a large ship,[/QUOTE]

So why then did you come here and start rudely demanding to be spoon fed numbers and explanations as if I was trying to hide or deny (in your own words) something?

Do your own homework or just go away.

[QUOTE=Capt. Phoenix;114758]Did you read the safety bulletin before acting like you know what you are talking about?[/QUOTE] If you know something better, then contribute that fact. Instead you posted a cheapshot. And contributed nothing informative to the discussion.

A nice person explains the concept rather than insult you. Irrelevant is a voltage between safety ground and the other two wires (as long as that voltage does not exceed 120 volts). An appliance connected to a reverse polarity wall receptacle (on land) would be 0 volts hot to to ground and 120 volts neutral to ground. No problem. For the same reason 0 volts neutral to ground and 60 volts neutral to ground is also good power; not a problem. All 120 volt appliances are designed so that all three voltages to safety ground are irrelevant.

The Coast Guard bulletin discusses something completely different. Above simply replies to, “Why would anyone wire a system so that ground was 60 volts from neutral?” Because it remains good power for 120 volt appliances.

Relevant is a voltage from safety ground to all other items in a building or on a ship. That voltage must remain at or almost at zero so that human life is not a risk - in a building or on a ship.

I was just trying to participate in a conversation I found interesting. I was not looking to be “spoon fed” any numbers. I was just interested in how this grounding system works and why it would be used when it can cause problems with some common equipment. I don’t know how you got the idea I was accusing you of denying or hiding anything. I apologize if that is how my posts came across. As far as doing my home work, every wiring diagram for delta system I can find shows the neutral grounded. If you know of a good place to find the information please let me know.

[QUOTE=“Steamer;114782”]

So why then did you come here and start rudely demanding to be spoon fed numbers and explanations as if I was trying to hide or deny (in your own words) something?

Do your own homework or just go away.[/QUOTE]

Westom was the one talking shit. Shadow is an innocent participant in the thread.