Power Strip

[chengkp75]

I was curious on this subject and after seeing one person publish a link to a Coast Guard paper on surge protectors and seeing another person saying that electricians would laugh about the article on surge protectors I decided to see what, if anything, Princess said about power strips and this is what I found.

 

Link to site on Princess.com:

 

http://www.princess.com/cruise-tips-vacation-ideas/cruise-destinations/cruise-tips-advice-and-information/packing-for-a-princess-cruise-vacation.html?zoom_highlight=power+strips#.VbAhOflBk-I

 

What is said on power strips at the above site:

 

"Because cruise trips are usually at least one week long, passengers should bring extra camera batteries and memory cards as well as a power strip to charge several electronics at once. "

 

This was the only hit that came up on a search of the Princess.com website for "power strip".

 

FYI.

 

Tom

 

Let me just restate something. I have been a ship's engineer for 40 years, including 4 years on cruise ships. I am the one who posted the USCG Safety Notice. I am not aware of the professional expertise of the poster who said that electricians would laugh at the article, nor am I aware of the expertise of the electricians to comment on marine electrical systems.

 

If you go to the "Ask a Cruise Question" forum, there is a thread there, "why are surge suppressors not allowed". Needless to say, I've posted all this there as well, and another CC member, Capt_BJ, who is an ex-USCG officer who has commanded USCG ships, has backed me up on this problem with surge suppressors.

 

Currently, I believe Carnival is the only line to actively state that surge suppressors are banned, but if you follow all the "power strip confiscated" threads on virtually every line's board, you will find that this is increasing, and the sole reason (since many lines will loan power strips after they have taken yours) is that yours has a surge suppressor and theirs doesn't, and their insurance wants them to stop the usage onboard.

 

Many folks feel that it is difficult to find a power strip without a surge suppresor, but this is not true, just google it, and many mistake the on/off switch or the circuit breaker for a surge suppressor. If there is a small LED

marked "protected" then it is surge protected. If there is no mention in the description of joule rating, then it is not surge protected. And many companies feed off the fears and experiences of people with older electronics that could not handle voltage changes (note I did not say spikes) as well, and would burn out with much smaller voltage changes, and continue to sell surge suppressors to "prevent this". The main reason for surge suppressors today is to protect against lightning strike, and many older or cheaper suppressors won't even do this.

[Pierlesscruisers]

Let me just restate something. I have been a ship's engineer for 40 years, including 4 years on cruise ships. I am the one who posted the USCG Safety Notice. I am not aware of the professional expertise of the poster who said that electricians would laugh at the article, nor am I aware of the expertise of the electricians to comment on marine electrical systems.

 

If you go to the "Ask a Cruise Question" forum, there is a thread there, "why are surge suppressors not allowed". Needless to say, I've posted all this there as well, and another CC member, Capt_BJ, who is an ex-USCG officer who has commanded USCG ships, has backed me up on this problem with surge suppressors.

 

Currently, I believe Carnival is the only line to actively state that surge suppressors are banned, but if you follow all the "power strip confiscated" threads on virtually every line's board, you will find that this is increasing, and the sole reason (since many lines will loan power strips after they have taken yours) is that yours has a surge suppressor and theirs doesn't, and their insurance wants them to stop the usage onboard.

 

Many folks feel that it is difficult to find a power strip without a surge suppresor, but this is not true, just google it, and many mistake the on/off switch or the circuit breaker for a surge suppressor. If there is a small LED

marked "protected" then it is surge protected. If there is no mention in the description of joule rating, then it is not surge protected. And many companies feed off the fears and experiences of people with older electronics that could not handle voltage changes (note I did not say spikes) as well, and would burn out with much smaller voltage changes, and continue to sell surge suppressors to "prevent this". The main reason for surge suppressors today is to protect against lightning strike, and many older or cheaper suppressors won't even do this.

 

I don't know if you quoted my post just to form a basis for what you wanted to say or what, but just let me go on record here and say that I wasn't arguing with what you or anybody else said, just that I had gotten curious about the subject of power strip use and wondered what Princess had to say on the subject of power strips. I listed what I found just as a point of interest, nothing more. I'm by no means an electrical expert of any sort and have never brought a power strip on a cruise with me nor do I plan to.

 

Tom

[jgpdx]

I don't know if you quoted my post just to form a basis for what you wanted to say or what, but just let me go on record here and say that I wasn't arguing with what you or anybody else said, just that I had gotten curious about the subject of power strip use and wondered what Princess had to say on the subject of power strips. I listed what I found just as a point of interest, nothing more. I'm by no means an electrical expert of any sort and have never brought a power strip on a cruise with me nor do I plan to.

 

Tom

 

I have an upcoming cruise this April on the Diamond and so I asked my TA at CruiseOne if she knew. She talked to someone she knows at Princess and indeed, power strips must be WITHOUT surge suppressors. By the way, the mini strips (3 outlets) have no switch, suppressors or breaker and are $2 at Home Depot or Ikea (I am sure at other stores also). Have a non-explosive cruise.:p

 

Jerry

[crochetcruise]

Have just purchased from The Reject Shop (cheap variety store here) both a 4 outlet power board-only has the sockets and the cord, so no switches at all and an extension cord of 3 metres (think it's about 10 feet) so I should be right. These will be kept in my suitcase-am thinking of taking measurements and looking for a designated storage unit, even a food storage container of an appropriate size would do, so I know I have charging capacity as long as I have access to a power point. I am still to purchase the adaptors, am getting both the 2 pin and 3 pin type so any combination is covered.

[NeonBud]

We use short ( less than 12 inch) extension cords and outlet expanders to accommodate the charging requirements. We also do not overload outlets by using regular appliances, such as a curling iron, on an outlet expander. We plug those sorts of things directly into an outlet as needed.

 

 

We also use an extension cord with 3 or 4 female connections. It works well for accessing the extra outlet behind the TV. Likewise we refrain from using high amp appliances like steamers and irons.

[AE_Collector]

Something to keep in mind is to try to leave an outlet available for the cabin steward's vacuum cleaner when you are out of the room. I feel for them when there is nowhere left to plug it in without having to second guess what to unplug in your room and risking the wrath of an irate passenger if he were to unplug the wrong thing.

 

I think they like to default to the outlet behind the TV for the vacuum when everything is in use on the desk but since many of us know about the TV outlet we may not be considering the steward when we leave the room. They likely wouldn't want to risk plugging the vacuum into a passengers power device either in case it is only designed for low current flows.

 

Terry

Edited July 24, 2015 by AE_Collector

[crochetcruise]

Something to keep in mind is to try to leave an outlet available for the cabin steward's vacuum cleaner when you are out of the room. I feel for them when there is nowhere left to plug it in without having to second guess what to unplug in your room and risking the wrath of an irate passenger if he were to unplug the wrong thing.

 

I think they like to default to the outlet behind the TV for the vacuum when everything is in use on the desk but since many of us know about the TV outlet we may not be considering the steward when we leave the room. They likely wouldn't want to risk plugging the vacuum into a passengers power device either in case it is only designed for low current flows.

 

Terry

 

THANK YOU!This is something I hadn't thought of, but makes a lot of sense! As a Fireman's daughter, I intend to only charge electrical items when I'm actually in the Suite for safety reasons. Paranoid? Possibly, but better safe than sorry!

[tetleytea]

I don't understand why power strips can be encouraged when they can be so easily confused with surge protectors. A surge protector can start a fire--and then it's goodbye quarter-million-dollar cabin. Seems like something you shouldn't be touching with a 10-foot pole.

[beg3yrs]

I don't understand why power strips can be encouraged when they can be so easily confused with surge protectors. A surge protector can start a fire--and then it's goodbye quarter-million-dollar cabin. Seems like something you shouldn't be touching with a 10-foot pole.

 

You've got a good point and that's probably why this particular thread just keeps going.

 

I suppose for those who just can't figure it out, it's better to skip it altogether.

 

I for one think the Cruise Critic folks do understand the bottom line and this thread is (finally) serving its purpose.

Edited July 25, 2015 by beg3yrs

[tetleytea]

I suppose for those who just can't figure it out, it's better to skip it altogether.

 

I wasn't aware of this problem until I read it on CC, but I figured it out when I read up on it because I had the same floating-ground problem when I was developing my own circuitry. It's a similar phenomenon as the surge protectors, except I wasn't dealing with ships--and I only fried a $7 card. The smoke was very impressive. :) I suspect, though, that nowadays on modern cruise ships you would probably only trip off a circuit breaker--not set a fire. A few staterooms would lose electricity, you would get educated by someone on cruise staff, you would have to pack away the surge protector.

[chengkp75]

I wasn't aware of this problem until I read it on CC, but I figured it out when I read up on it because I had the same floating-ground problem when I was developing my own circuitry. It's a similar phenomenon as the surge protectors, except I wasn't dealing with ships--and I only fried a $7 card. The smoke was very impressive. :) I suspect, though, that nowadays on modern cruise ships you would probably only trip off a circuit breaker--not set a fire. A few staterooms would lose electricity, you would get educated by someone on cruise staff, you would have to pack away the surge protector.

 

You sound like you are in the electronics field. Perhaps I could interest you in joining the thread on the "Ask a Cruise Question" forum started by Cowboy Tex, who wants an explanation as to why a surge protector behaves this way in marine electrical systems. I have tried my best, but I am by far not an EE, and its been a long time since I've taken classes in electrical theory. I deal in hands on electrical maintenance, not theory.

[Treven]

I just bought one. Looking forward to checking it out, "up close and personal". It looks like it will be an ongoing fixture in my travel bag.

My power strip arrived yesterday from Victorinox - the Swiss Army folks. It is a compact, travel unit. It has a 16" heavy duty power cord, three grounded plug-ins (for my lack of a better term), and a USB port. I think this is going to work out just fine to charge my laptop, camera, iPad and iPhone (when necessary).

Edited July 25, 2015 by Treven

[CowboyTex]

You sound like you are in the electronics field. Perhaps I could interest you in joining the thread on the "Ask a Cruise Question" forum started by Cowboy Tex, who wants an explanation as to why a surge protector behaves this way in marine electrical systems. I have tried my best, but I am by far not an EE, and its been a long time since I've taken classes in electrical theory. I deal in hands on electrical maintenance, not theory.

 

Hi chengkp75,

 

During our discussion on the “Ask a Cruise Question” forum you suggested I take a look at this thread here on Princess. You were right as some of these postings are right on target.

 

I’m afraid I have not made myself clear in defining the question over which I am stumped. It is why using a power strip containing a SPD, a surge protection device, (which may help solve an electrical problem in certain cases but not help in other cases) is unacceptable while a similar power strip without any protection whatsoever, is acceptable. I don’t understand why protection from some problems, albeit it only a few, is worse than no protection al all.

 

On this thread, sptrout (in posting #31) gives a link to an excellent article on “potential problems” with using SPDs. The author, who is an electrical engineer in the Coast Guard, clearly explains a situation in which a power strip containing a SPD, is in a circuit in which a failure of an electric toaster permits excessive currents to flow and causes a potential meltdown. When reading this article quickly, it appears as though the SPD has caused the problem. But on further study, it becomes apparent that the SPD has had nothing whatever to do with starting the problem and has not contributed in any way, to the problem. It is simply that the SPD did not prevent or solve the problem. If there had been no SPD in the power strip, the same problem would have occurred with the same result. Only in this case, the resulting meltdown might have been in the coffee pot instead of in the power strip containing the SPD.

 

By the way, in my opinion, the Marine Safety Alert #03-13b is similar to the above article in that it does not contain the necessary information to conclude that the fires experienced were due to the presence of SPDs. The Safety Alert only alleges that there were SPDs in the circuit and that they caused the problem. No information is given as to any unreliable circuit configuration or any mechanism by which excessive currents were permitted to flow. From the information given, the problem could easily have been simply a manufacturing defect in the power strips containing the SPDs that had nothing to do with the SPDs themselves.

 

I really need to repeat here the old adage of “the plural of “anecdote” is not “data”. Yes, there have been meltdowns and fires with power strips containing SPDs. I imagine there have also been meltdowns and fires with power strips that did not contain SPDs. Anecdotal evidence of problems with SPDs does not demonstrate the necessity of banning their use. A little science here would be desirable.

 

I do need to affirm here that when on a cruise ship, I believe the use of a power strip containing a dual switch circuit breaker (both power lines) is significantly wiser than the use of a power strip containing only a SPD. This is because different types of problems can be protected against. Of course when both a dual switch circuit breaker and a SPD are incorporated into a single package, we have the basic design of a “Marine SPD” which is approved by all parties for shipboard use.

 

So to finish my little epistle, perhaps someone on this board can explain to me why when used on a ship, a power strip with a SPD (that includes MOVs and a fuse), the kind built into almost all power strips sold in the USA and used in virtually every house in the country, is worse than the use of a power strip that doesn’t have a SPD included. I understand the SPD will not replace a circuit breaker or protect against problems caused by various external circuit faults, but neither will a power strip without a SPD (or a simple multi- receptacle extension cord for that matter.) Yet the power strip without the SPD is acceptable while the strip with the SPD is not. Could someone please help me to understand why no protection is better than some protection, no matter how little.

 

Tex

[chengkp75]

Hi chengkp75,

 

During our discussion on the “Ask a Cruise Question” forum you suggested I take a look at this thread here on Princess. You were right as some of these postings are right on target.

 

I’m afraid I have not made myself clear in defining the question over which I am stumped. It is why using a power strip containing a SPD, a surge protection device, (which may help solve an electrical problem in certain cases but not help in other cases) is unacceptable while a similar power strip without any protection whatsoever, is acceptable. I don’t understand why protection from some problems, albeit it only a few, is worse than no protection al all.

 

On this thread, sptrout (in posting #31) gives a link to an excellent article on “potential problems” with using SPDs. The author, who is an electrical engineer in the Coast Guard, clearly explains a situation in which a power strip containing a SPD, is in a circuit in which a failure of an electric toaster permits excessive currents to flow and causes a potential meltdown. When reading this article quickly, it appears as though the SPD has caused the problem. But on further study, it becomes apparent that the SPD has had nothing whatever to do with starting the problem and has not contributed in any way, to the problem. It is simply that the SPD did not prevent or solve the problem. If there had been no SPD in the power strip, the same problem would have occurred with the same result. Only in this case, the resulting meltdown might have been in the coffee pot instead of in the power strip containing the SPD.

 

By the way, in my opinion, the Marine Safety Alert #03-13b is similar to the above article in that it does not contain the necessary information to conclude that the fires experienced were due to the presence of SPDs. The Safety Alert only alleges that there were SPDs in the circuit and that they caused the problem. No information is given as to any unreliable circuit configuration or any mechanism by which excessive currents were permitted to flow. From the information given, the problem could easily have been simply a manufacturing defect in the power strips containing the SPDs that had nothing to do with the SPDs themselves.

 

I really need to repeat here the old adage of “the plural of “anecdote” is not “data”. Yes, there have been meltdowns and fires with power strips containing SPDs. I imagine there have also been meltdowns and fires with power strips that did not contain SPDs. Anecdotal evidence of problems with SPDs does not demonstrate the necessity of banning their use. A little science here would be desirable.

 

I do need to affirm here that when on a cruise ship, I believe the use of a power strip containing a dual switch circuit breaker (both power lines) is significantly wiser than the use of a power strip containing only a SPD. This is because different types of problems can be protected against. Of course when both a dual switch circuit breaker and a SPD are incorporated into a single package, we have the basic design of a “Marine SPD” which is approved by all parties for shipboard use.

 

So to finish my little epistle, perhaps someone on this board can explain to me why when used on a ship, a power strip with a SPD (that includes MOVs and a fuse), the kind built into almost all power strips sold in the USA and used in virtually every house in the country, is worse than the use of a power strip that doesn’t have a SPD included. I understand the SPD will not replace a circuit breaker or protect against problems caused by various external circuit faults, but neither will a power strip without a SPD (or a simple multi- receptacle extension cord for that matter.) Yet the power strip without the SPD is acceptable while the strip with the SPD is not. Could someone please help me to understand why no protection is better than some protection, no matter how little.

 

Tex

 

Last time. Firstly, the article linked in post #31 only deals with ground issues, and no where in his example does he mention that the power strip has a surge protector. He is explaining why not only should surge suppressors not be used, but a non-marine power strip as well (two pole breaker).

 

Now, as I've said, I cannot provide you with the explanation you require, and as a poster on that thread asked, why don't you take this to an electrical engineer's forum, ask this question, get a response, either positive or negative, and come back to us, who are not electrical engineers. By your assertions, you are claiming a negative ("I don't understand how it can cause a problem, so therefore it can't cause one) to prove your case, it seems to me. Obviously, while perhaps the USCG SN and the link in post #31 do not reveal the reason that SPD's should not be used in marine electrical systems, does not mean that the reason does not exist. As the poster on the other thread suggested, why not contact Texas Maritime to see if one of their professors can answer your question.

 

So, to end my epistle, no, no one on this forum can explain it to you, but then again, this is a cruise forum, not an electrical theory forum.

Edited July 25, 2015 by chengkp75

[ccrain]

Most US based 120VAC electrical power devices are tested to 600V insulation value. That is most will not arc from hot to ground (or neutral) until 600V is exceeded. By installing a surge arrestor you deliberately insert a lower breakdown voltage. So if the line voltage exceeds the breakdown voltage of the surge arrestor the surge arrestor will conduct current and generate heat. (V=I*R).

 

For example, let's say one installs a SPD designed for a 120VAC circuit into a 220VAC circuit. Bad things happen. Also keep in mind that 120VAC (RMS Voltage) =170V zero to peak and 340V peak to peak. 220VAC (RMS) = 310V zero to peak and 620V peak to peak. That's a LOT of voltage to mess around with.

 

Now add in the way ships are wired, as opposed to the US under the National Electric Code, with weird neutrals, floating grounds, deltas, wyes, and a whole bunch of Electrical Engineering black magic - because remember THERE IS NO EARTH GROUND on a ship - , and then add in all the weird loads and turn on, turn off transients that can occur on a ship, and you have a recipe for easily overvolting an SPD in a circuit that would otherwise be fine.

 

A MOV based SPD can fail in a number of ways, but typically the failure mode is shorted to "ground, then blows open, BUT if the energy during the failure cycle is not enough to blow the MOV open, it could melt and become a high resistance connection to ground - read HEATER!

 

A lot of people think fuses and breakers will pop or trip when this occurs, but not necessarily. Most thermal breakers will typically pop in 3-5 cycles of 50/60Hz power when the current draw exceeds their design load - typically 85 to 90% of their rating. Fuses require a very specific waveform to blow, but typically are a thermal device much like a thermal breaker. Some of the newer magnetic breakers or arc detect breakers trip on rise rate of the current - as in a very rapidly increasing current means a short has occurred. These react much faster - but they are expensive, required in a lot of new construction, but not used as much in the past.

 

But if an MOV becomes a high impedance to ground, the breaker or fuse may not ever trip! Again, its a matter of V=I*R. The volts will remain pretty constant, the R may remain high for several minutes before it completely melts down and opens up, which means the current could remain low enough to keep from tripping the breaker.

 

A 20 amp 120VAC line can pretty much put 18 amps into something forever, generating around 2kW of heat.

 

That's a blow drier on steroids.

 

Bottom line - using a Commercial Off The Shelf SPD protected power strip on a ship introduces a potential fault inherent in the SPD itself that would not be there on an unprotected power strip.

[chengkp75]

Most US based 120VAC electrical power devices are tested to 600V insulation value. That is most will not arc from hot to ground (or neutral) until 600V is exceeded. By installing a surge arrestor you deliberately insert a lower breakdown voltage. So if the line voltage exceeds the breakdown voltage of the surge arrestor the surge arrestor will conduct current and generate heat. (V=I*R).

 

For example, let's say one installs a SPD designed for a 120VAC circuit into a 220VAC circuit. Bad things happen. Also keep in mind that 120VAC (RMS Voltage) =170V zero to peak and 340V peak to peak. 220VAC (RMS) = 310V zero to peak and 620V peak to peak. That's a LOT of voltage to mess around with.

 

Now add in the way ships are wired, as opposed to the US under the National Electric Code, with weird neutrals, floating grounds, deltas, wyes, and a whole bunch of Electrical Engineering black magic - because remember THERE IS NO EARTH GROUND on a ship - , and then add in all the weird loads and turn on, turn off transients that can occur on a ship, and you have a recipe for easily overvolting an SPD in a circuit that would otherwise be fine.

 

A MOV based SPD can fail in a number of ways, but typically the failure mode is shorted to "ground, then blows open, BUT if the energy during the failure cycle is not enough to blow the MOV open, it could melt and become a high resistance connection to ground - read HEATER!

 

A lot of people think fuses and breakers will pop or trip when this occurs, but not necessarily. Most thermal breakers will typically pop in 3-5 cycles of 50/60Hz power when the current draw exceeds their design load - typically 85 to 90% of their rating. Fuses require a very specific waveform to blow, but typically are a thermal device much like a thermal breaker. Some of the newer magnetic breakers or arc detect breakers trip on rise rate of the current - as in a very rapidly increasing current means a short has occurred. These react much faster - but they are expensive, required in a lot of new construction, but not used as much in the past.

 

But if an MOV becomes a high impedance to ground, the breaker or fuse may not ever trip! Again, its a matter of V=I*R. The volts will remain pretty constant, the R may remain high for several minutes before it completely melts down and opens up, which means the current could remain low enough to keep from tripping the breaker.

 

A 20 amp 120VAC line can pretty much put 18 amps into something forever, generating around 2kW of heat.

 

That's a blow drier on steroids.

 

Bottom line - using a Commercial Off The Shelf SPD protected power strip on a ship introduces a potential fault inherent in the SPD itself that would not be there on an unprotected power strip.

 

This tired old boat mechanic thanks you for your explanation. If I may be so bold as to ask you if the existence of two single phase circuits fed from different legs of a 3-phase distribution could also lead to the overvolting of the SPD that you describe? Not trying for Tex's level of information, but just curious.

[CowboyTex]

Most US based 120VAC electrical power devices are tested to 600V insulation value. That is most will not arc from hot to ground (or neutral) until 600V is exceeded. By installing a surge arrestor you deliberately insert a lower breakdown voltage. So if the line voltage exceeds the breakdown voltage of the surge arrestor the surge arrestor will conduct current and generate heat. (V=I*R).

 

For example, let's say one installs a SPD designed for a 120VAC circuit into a 220VAC circuit. Bad things happen. Also keep in mind that 120VAC (RMS Voltage) =170V zero to peak and 340V peak to peak. 220VAC (RMS) = 310V zero to peak and 620V peak to peak. That's a LOT of voltage to mess around with.

 

Now add in the way ships are wired, as opposed to the US under the National Electric Code, with weird neutrals, floating grounds, deltas, wyes, and a whole bunch of Electrical Engineering black magic - because remember THERE IS NO EARTH GROUND on a ship - , and then add in all the weird loads and turn on, turn off transients that can occur on a ship, and you have a recipe for easily overvolting an SPD in a circuit that would otherwise be fine.

 

A MOV based SPD can fail in a number of ways, but typically the failure mode is shorted to "ground, then blows open, BUT if the energy during the failure cycle is not enough to blow the MOV open, it could melt and become a high resistance connection to ground - read HEATER!

 

A lot of people think fuses and breakers will pop or trip when this occurs, but not necessarily. Most thermal breakers will typically pop in 3-5 cycles of 50/60Hz power when the current draw exceeds their design load - typically 85 to 90% of their rating. Fuses require a very specific waveform to blow, but typically are a thermal device much like a thermal breaker. Some of the newer magnetic breakers or arc detect breakers trip on rise rate of the current - as in a very rapidly increasing current means a short has occurred. These react much faster - but they are expensive, required in a lot of new construction, but not used as much in the past.

 

But if an MOV becomes a high impedance to ground, the breaker or fuse may not ever trip! Again, its a matter of V=I*R. The volts will remain pretty constant, the R may remain high for several minutes before it completely melts down and opens up, which means the current could remain low enough to keep from tripping the breaker.

 

A 20 amp 120VAC line can pretty much put 18 amps into something forever, generating around 2kW of heat.

 

That's a blow drier on steroids.

 

Bottom line - using a Commercial Off The Shelf SPD protected power strip on a ship introduces a potential fault inherent in the SPD itself that would not be there on an unprotected power strip.

 

Hi ccrain,

 

I have seen your postings previously and they have been thoughtful. I appreciate your input.

 

As you assert, yes, it is certainly possible for MOV based SPDs to fail in power strips in 110 VAC systems. But the total amount of commercial experience says although possible, it is not a significant or even a recognizable, problem. It is difficult to imply there is a problem when << a power strip with a SPD (that includes MOVs and a fuse), the kind built into almost all power strips sold in the USA and used in virtually every house in the country >> is being used daily on 110 VAC electrical systems in probably millions of homes. The power strips are designed with safety factors to operate in 110 VAC systems and comply with all safety requirements. With the number of strips having daily been used for years in the USA, if there were a reliability problem, it certainly would have come out by now. I don’t think it is reasonable to assert that power strips incorporating SPDs are not safe at home. So as long as they are used in systems with steady state voltages no greater than 110 VAC, I don’t understand the problem.

 

Yes, shipboard electrical systems use a different grounding scheme (which by the way is certainly not << a whole bunch of Electrical Engineering black magic>>), but I don’t see where this has any effect whatever on the reliability of SPDs. You of course know that all electric utility companies use delta and wye connections in all of their power transmission lines and floating (non earth touching) grounds are a standard wiring technique in many special electrical systems, including virtually every RV (Recreational Vehicle) on the road. But I’m afraid I am not familiar with the meaning of <<weird neutrals>> or << all the weird loads and turn on, turn off transients that can occur on a ship>>.

 

You also bring up the possibility of transient voltage spikes in a ship’s electrical system. If spikes are present, this is exactly what the SPD’s are designed to protect against (albeit in only one power line). Without a SPD, if there were indeed a large transient spike on a ship’s electrical system, a whole bunch of electrical devices might well fail.

 

To demonstrate a problem, you say <<For example, let's say one installs a SPD designed for a 120VAC circuit into a 220VAC circuit. Bad things happen.>> You bet bad things can happen. But let me alter your statement just a bit to say “let's say one installs ANYTHING designed for a 120VAC circuit into a 220VAC circuit. Bad things can happen.” I do not understand what this proves, other than that people can do dumb things. I know of no protection, other than circuit breakers, for 110 VAC appliances being connected to a 220 VAC line. If a cruiser plugs a nightlight, clock, electric shaver, or any other 110 VAC appliance into the 220 VAC receptacle on a cabin wall, it is very likely that smoke will arise from somewhere, whether or not SPDs are present.

 

In describing possible problems caused by SPDs, you also make the assertion that potentially << you have a recipe for easily overvolting an SPD in a circuit that would otherwise be fine.>> Although I am not familiar with the expression “overvolting an SPD”, I will assume it means subjecting the SPD to a voltage high enough that the SPD will start to conduct some current in an attempt to reduce the excess voltage. If this is indeed the meaning, then I do not believe this is a problem. The voltage at which modern SPDs start to conduct current is in the 300 to 500 volt range. And virtually any 110 VAC circuit experiencing a non-transient 300 to 500 volt signal, would most certainly not <<be fine>>, irrespective of any SPDs present. The circuit would most probably, in the vernacular, simply burn out.

 

Finally, if I understand your concluding statement correctly, you are asserting that the reason power strips containing SPDs should not be allowed on ships is because if SPDs are present, they may fail and if they are not present then of course they cannot fail. Your logic here is perfectly sound.

 

The counter to this is that with the probably hundreds of millions of operating hours in homes throughout the USA and indeed throughout the entire world, no reliability problems with SPDs have been identified. So is it reasonable to prohibit a device when there is no direct evidence of (or any theory that identifies) any specific problem. Power strips incorporating SPDs are the least expensive and most common type of strip available today and they do offer some, albeit not very much, level of protection. Also, the vast majority of cruisers have them.

 

ccrain, I really do thank you for taking the time and energy apparent in your posting. I believe that it is only with communications such as these, from knowledgeable individuals such as yourself, that we can reach the solutions to our various problems. I do appreciate your thoughts.

 

So I guess the question really comes down to “are we chasing an urban legend?”

 

Tex

[chengkp75]

Hi ccrain,

 

So I guess the question really comes down to “are we chasing an urban legend?”

 

Tex

 

No, I think you believe you are chasing an urban legend, since you persist in searching for answers on a non-technical forum. Since you seem to have difficulty with the USCG Safety Notice, why don't you contact the USCG's Office of Design and Engineering Standards:

 

http://www.uscg.mil/hq/cg5/cg521

 

Or the Office of Investigations and Casualty Analysis, USCG Headquarters which developed the Safety Alert:

 

http://www.uscg.mil/hq/cg5/cg545

 

or the Inspections and Compliance Directorate:

 

http://www.uscg.mil/hq/cg5/cg54

 

Here's the department head of Marine Engineering Systems at Texas A&M:

 

John Sweetman: sweetmaj@tamug.edu

 

Head of Marine Engineering deparment, US Merchant Marine Academy:

 

Capt. Joseph Poliseno: (516) 726-5732

 

Head of Marine Engineering department, Mass. Maritime Academy:

 

George Howe: ghowe@maritime.edu

 

Hopefully, as I have said before, you can find your answers, either proving you right or the experts right, at one or more of these assets.

 

For me, I'm tired of providing you with avenues of research you should have been pursuing yourself, and I hope that no further CC member waste their time answering this thread until you come back with responses from at least a few of these people.

 

For me, and I think a lot of CC members, we will stick with the recommendations of the USCG, whether they explain it fully or not, or whether we understand it fully or not.

[ccrain]

This tired old boat mechanic thanks you for your explanation. If I may be so bold as to ask you if the existence of two single phase circuits fed from different legs of a 3-phase distribution could also lead to the overvolting of the SPD that you describe? Not trying for Tex's level of information, but just curious.

 

I was introduced to a "corner grounded" delta transformer issue several years ago. One of those EE black magic thingies I go "HUUHHHH" about. It appears that on a DELTA distribution system, if you ground one leg, the other two can go to 2x the peak voltage!

 

And it actually happened on one system I was working on. We could not understand why MOVs were literally melting down on high and low speed fan motor circuits. We had to use MOVs that had 2x the voltage rating to get them to quit melting. As it turned out the "starter circuits" for the fan motors simulated a temporary short to ground on one leg of the delta power to the motors. This spiked the voltage in the other leg, which caused the protective MOVs to shunt the excess to their ground. After many days of this, the MOV would eventually heat and melt down. And we are talking industrial 60mm MOVs that are about 5" high, 4" wide and an inch thick. We had to go from 480V rated MOVs to 880V rated MOVs to get them to quit melting down.

 

On a "normal" installation, without any MOVs, this would not be an issue, but because we put an MOV in the circuit that was a lower voltage than the voltages the circuit could generate, we introduced a failure mode.

 

We in the engineering community refer to this as a Murphy in which Mr. Murphy roundly kicks your rear end up around your shoulders.

[ccrain]

This discussion has peaked my curiosity. So I perused the testing standards required of Marine SPD's. Mainly ASTM F 1507. I see now the major differences between normal land based system SPDs and those specifically tested for Marine applications.

 

Its actually made clear in Appendix XI:

 

X1.1 Shipboard Electrical Systems Environment:

X1.1.1 Transient voltage surge suppressors (TVSS) devices

work better and can more effectively shunt damaging transient

overvoltages and current pulses to electronic equipment, if

system grounding is done properly and has good integrity.

Therein lies the major problem with TVSS devices for shipboard

use. Unlike industrial or commercial electrical systems

which have an ac supply ground and an equipment ground,

most shipboard electrical systems are “ungrounded.”Without a

system ground (normally referred to as the neutral or common),

then shipboard TVSS devices have protective modes

that are limited to line-to-line and/or line-to-ground shunting of

transients. Equipment (safety) grounds are achieved by proper

mounting of equipment to the ship’s metal hull or structure or

installation of grounding straps between the hull and isolated

equipment. The effectiveness of shipboard TVSS will be highly

dependent on the equipment grounding techniques.

 

This "clarification" in 1507 leads to two distinctly different requirements in shipboard SPD performance. These are that:

 

a) The SPD is required to have a voltage protection level of almost 3x the RMS line voltage (120VAC=350V, 208/240V = 700V and 480V= 1200V.

 

b) The SPD is REQUIRED to have overcurrent protection AND overtemperature protection. This is significant in that while some, but not all, household SPDs have overcurrent protection, they do not have over temperature protection.

 

So the answer is that unless your SPD is ASTM F 1507 compliant, and no one could ever know that from basic packaging, don't plug it into the shipboard systems. So I prefer to follow the 'don't use an SPD' in my cabin procedures...

[CowboyTex]

I was introduced to a "corner grounded" delta transformer issue several years ago. One of those EE black magic thingies I go "HUUHHHH" about. It appears that on a DELTA distribution system, if you ground one leg, the other two can go to 2x the peak voltage!

 

And it actually happened on one system I was working on. We could not understand why MOVs were literally melting down on high and low speed fan motor circuits. We had to use MOVs that had 2x the voltage rating to get them to quit melting. As it turned out the "starter circuits" for the fan motors simulated a temporary short to ground on one leg of the delta power to the motors. This spiked the voltage in the other leg, which caused the protective MOVs to shunt the excess to their ground. After many days of this, the MOV would eventually heat and melt down. And we are talking industrial 60mm MOVs that are about 5" high, 4" wide and an inch thick. We had to go from 480V rated MOVs to 880V rated MOVs to get them to quit melting down.

 

On a "normal" installation, without any MOVs, this would not be an issue, but because we put an MOV in the circuit that was a lower voltage than the voltages the circuit could generate, we introduced a failure mode.

 

We in the engineering community refer to this as a Murphy in which Mr. Murphy roundly kicks your rear end up around your shoulders.

 

Hi ccrain,

 

Very interesting problem and solution to the system with a corner grounded delta transformer. I’m glad you found a simple method to solve the problem. Ordinarily, this problem would not be expected to occur in a delta wired three phase distribution system or in a corner grounded delta wired three phase distribution system. Grounding one leg of a delta wired distribution system, used to be an ordinary circuit configuration for specific applications (that is not too prevalent these days,) with no double peak voltages commonly being encountered. But Murphy does have a habit of being a rather pesky individual.

 

However, before we go criticizing the MOVs for not having sufficient safety factors for operating in the system, let’s look at the words “corner grounded delta TRANSFORMER”. With a transformer in the circuit, as opposed to a straight non-transformer corner grounded delta distribution system, and <<the fan motors simulated a temporary short to ground on one leg of the delta power to the motors>>, of course a rapid short circuit from almost ANYTHING to ANYTHING in a transformer circuit is likely to create a significant transient pulse (when considering the inherent inductive nature of transformer coils). This could easily have been foreseen and no, it is not << One of those EE black magic thingies.>> But in your particular case, the transient pulse could easily have been greater than anticipated. However, without the significant inductance of the transformer coils, I immediately cannot think of a reason why the voltage between the two ungrounded legs in a grounded delta distribution system connection, would go to double the ordinary system peak voltage.

 

Your problem and its solution are a good example of an engineering failure analysis and corrective action. It’s good that you did find such an elegant solution. But realize that if the MOVs hadn’t failed, it might well have been extremely likely that, due to the surges, the fan motors or some other element in the circuit, might have failed eventually.

 

Here also, as appliances and devices are designed for specific operating voltages, a circuit that creates significant voltage surges above this value, may well cause devices in the circuit (which have not been designed to withstand the circuit surges,) to fail. But I can see no construction weakness actually being attributed to the action of modern SPDs. In this case, they just simply may have been doing their job.

 

Tex

[tetleytea]

Here's the department head of Marine Engineering Systems at Texas A&M:

 

I think you didn't want to refer to non-technical forums? :p

[CowboyTex]

This discussion has peaked my curiosity. So I perused the testing standards required of Marine SPD's. Mainly ASTM F 1507. I see now the major differences between normal land based system SPDs and those specifically tested for Marine applications.

 

Its actually made clear in Appendix XI:

 

X1.1 Shipboard Electrical Systems Environment:

X1.1.1 Transient voltage surge suppressors (TVSS) devices

work better and can more effectively shunt damaging transient

overvoltages and current pulses to electronic equipment, if

system grounding is done properly and has good integrity.

Therein lies the major problem with TVSS devices for shipboard

use. Unlike industrial or commercial electrical systems

which have an ac supply ground and an equipment ground,

most shipboard electrical systems are “ungrounded.”Without a

system ground (normally referred to as the neutral or common),

then shipboard TVSS devices have protective modes

that are limited to line-to-line and/or line-to-ground shunting of

transients. Equipment (safety) grounds are achieved by proper

mounting of equipment to the ship’s metal hull or structure or

installation of grounding straps between the hull and isolated

equipment. The effectiveness of shipboard TVSS will be highly

dependent on the equipment grounding techniques.

 

This "clarification" in 1507 leads to two distinctly different requirements in shipboard SPD performance. These are that:

 

a) The SPD is required to have a voltage protection level of almost 3x the RMS line voltage (120VAC=350V, 208/240V = 700V and 480V= 1200V.

 

b) The SPD is REQUIRED to have overcurrent protection AND overtemperature protection. This is significant in that while some, but not all, household SPDs have overcurrent protection, they do not have over temperature protection.

 

So the answer is that unless your SPD is ASTM F 1507 compliant, and no one could ever know that from basic packaging, don't plug it into the shipboard systems. So I prefer to follow the 'don't use an SPD' in my cabin procedures...

 

Hi ccrain,

 

Our discussion here has also stimulated my curiosity. I really appreciate your comments and suggestions.

 

You quote some information from ASTM-F-1507 that, unfortunately, I have not seen. However, from the paragraphs presented, I cannot agree completely with the assertion of << Unlike industrial or commercial electrical systems which have an ac supply ground and an equipment ground, most shipboard electrical systems are “ungrounded.” Without a system ground (normally referred to as the neutral or common)>>

 

In the above citing from your posting, for commercial and industrial systems, I understand that the <<ac supply ground>> line is clearly defined as separate and different from the <<equipment ground>> line. Further, I assume that by an <<equipment ground>>, you are referring to the ship’s hull. If this is indeed the case, then I am under the impression that, contrary to the assertion made above, shipboard electrical systems most certainly do have a well defined <<system ground.>> It is the “Neutral” line connected electrically between the two 110 VAC power lines. By the above terminology, I believe this this “Neutral” wire (that is also connected back to the ship’s electrical generator,) would be defined as the <<system ground>> that is asserted not to exist. This “neutral wire” is completely separate and independent from the ship’s <<equipment ground>> (the ship’s hull.)

 

One of the initial sentences and the final sentence cited, reveal what I imagine to be the purpose of the ASTM specification, and summarize my quandary << Transient voltage surge suppressors (TVSS) devices work better and can more effectively shunt damaging transient overvoltages…>> and <<The effectiveness of shipboard TVSS will be highly dependent on the equipment grounding techniques.>> As I have discussed previously with analyses in other posts, the ASTM specification appears to deal with the effectiveness of SPDs in preventing problems, rather than concentrating on any weaknesses or problems caused by their use. We are not speaking here about their effectiveness in preventing potential problems, we are looking for realistic problems that may be caused by, or accentuated by, their use. And thus far, I have not been able to find any.

 

Finally, I am having some difficulty in going from the specification cited to the two recommendations presented. I would greatly appreciate any information you have on the reasoning behind, and the analysis or data that prompted, the two recommendations. Without this information, unfortunately, I cannot comment on the urgency or necessity of complying with the recommendations. Unfortunately, even as a past member of ASTM and IEEE and a Registered Professional Engineer in the State of California, ASTM still charges a fee to download a copy of their spec, ASTM-F-1507. By the way, being a Registered Professional Engineer implies that with a $10 bill I can probably get a cup of coffee at a Starbucks, but it did give me the ability to approve the plans for specific types of public works projects in the State of California. If you have a copy of the ASTM spec., I’d appreciate your sending a copy along for me to peruse. If you agree, I’ll be glad to give you my E-mail address.

 

In either case, I do agree with you that realistically, there is no practical way to know whether or not a specific power strip is compliant with the construction and testing requirements of ASTM-F 1507, as that information is not available commonly.

 

Take care, my friend, and thanks for your help.

 

Tex

[ccrain]

The quotes I provided were directly out of the ASTM F-1507-99 document. The other requirements are also right out of the ASTM document.

 

I'm not passing judgment on them or analyzing them, just presenting the requirements as stated.

 

Right or wrong, I can now see how an ASTM 1507 compliant SPD would differ substantially from a COTS SPD from Walmart/Office Depot, etc. - the prime difference being the Temperature disconnect requirement.

 

I just looked at all the ones we have here in the office and none have a temperature sensor and only a few have an in-line overcurrent breaker. None have fuses. None of mine at home have temperature sensors either.

[CowboyTex]

No, I think you believe you are chasing an urban legend, since you persist in searching for answers on a non-technical forum. Since you seem to have difficulty with the USCG Safety Notice, why don't you contact the USCG's Office of Design and Engineering Standards:

 

http://www.uscg.mil/hq/cg5/cg521

 

Or the Office of Investigations and Casualty Analysis, USCG Headquarters which developed the Safety Alert:

 

http://www.uscg.mil/hq/cg5/cg545

 

or the Inspections and Compliance Directorate:

 

http://www.uscg.mil/hq/cg5/cg54

 

Here's the department head of Marine Engineering Systems at Texas A&M:

 

John Sweetman: sweetmaj@tamug.edu

 

Head of Marine Engineering deparment, US Merchant Marine Academy:

 

Capt. Joseph Poliseno: (516) 726-5732

 

Head of Marine Engineering department, Mass. Maritime Academy:

 

George Howe: ghowe@maritime.edu

 

Hopefully, as I have said before, you can find your answers, either proving you right or the experts right, at one or more of these assets.

 

For me, I'm tired of providing you with avenues of research you should have been pursuing yourself, and I hope that no further CC member waste their time answering this thread until you come back with responses from at least a few of these people.

 

For me, and I think a lot of CC members, we will stick with the recommendations of the USCG, whether they explain it fully or not, or whether we understand it fully or not.

 

chengkp75,

 

Whoa, whoa big fella. Don’t get your spur caught in a stirrup.

 

I’m on this board because you recommended I come over here from the “Ask a Cruise Question” board. I appreciate the suggestions you’ve been providing and I’m in the process of contacting several of the individuals on your list.

 

But don’t I have the freedom here to answer other posts that are being presented? It’s a wide prairie out there and there’s plenty of space for all kinds of farmers, cowmen and even sheep herders.

 

As Laura Bush once said to George W. (off camera of course,) “Rein it in, Bubba, and let the horse run.”

 

Tex