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Old 15-04-2013, 11:32   #1
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Power strip dangers

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. However, The Coast Guard has just published a Marine Safety Alert concerning using these devices, usually designed only for shoreside applications, on board. Because most SPDs interrupt only the hot conductor when a surge occurs. This could lead to an imbalance through the distribution panel, and resulted in a fire.
Here is a link to the USCG alert:

http://wow.uscgaux.info/Uploads_wowI...ve_Devices.pdf

Since we are the boaters most likely to have this type of device, I thought I'd share it with you.

PS: I am a newbie to this site and being a licensed engineer, an amateur boat designer and a weekend volunteer Coastie, I get information like this frequently.
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Old 15-04-2013, 11:58   #2
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Re: Power strip dangers

There is a bit of confusion with the term power surge. It is actually a voltage spike that they are designed to reduce or eliminate. They also act as a breaker to limit how much current the loads can draw, usually 15 amps for most of them. Power is drawn through an electrical circuit according to the resistance of the load and not forced through an electrical circuit.

You always want the AC breakers on a boat to protect both the hot and neutral wires, one breaker for each (double pole) mechanically connected to each other so that if one trips they both trip.

If it were a pipe, think of voltage as water pressure and current as the amount of water flowing through the pipe.
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Old 15-04-2013, 12:22   #3
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Re: Power strip dangers

Quote:
Originally Posted by David M View Post

You always want the AC breakers on a boat to protect both the hot and neutral wires, one breaker for each (double pole) mechanically connected to each other so that if one trips they both trip.
I believe most all marine AC panels have double pole breakers only on the Mains side, not the Branch Circuit side. On my Blue Sea panel the Branch Breakers protect the hot side only.
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Old 15-04-2013, 13:13   #4
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Re: Power strip dangers

Quote:
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.
this is the electrical gobbledi-gook thats is teh USCG report, as an EE I havent a clue what they mean.

surge protection typically has MOV devices that sit accross live and neutral, they crowbar them together briefly in a surge situation, how this could afect anything on a typical yacht is beyond my simple electronic brain.

Dave
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Old 15-04-2013, 20:30   #5
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Re: Power strip dangers

Quote:
Originally Posted by goboatingnow View Post
this is the electrical gobbledi-gook thats is teh USCG report, as an EE I havent a clue what they mean.

surge protection typically has MOV devices that sit accross live and neutral, they crowbar them together briefly in a surge situation, how this could afect anything on a typical yacht is beyond my simple electronic brain.

Dave
Doesn't make sense to me either (also an EE). What unbalanced load are they talking about? If the hot side is opened, either by a surge protector or a circuit breaker, then there is no current flow in the system so nothing to unbalance.

I guess there could be some other fault in the system like a short between the hot and ground or neutral but that would have nothing to do with a surge protector.
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Old 16-04-2013, 05:56   #6
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Re: Power strip dangers

Greetings and welcome aboard the CF, GLtrawler.

Thanks for the info'.
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Old 16-04-2013, 06:06   #7
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Re: Power strip dangers

welcome to cf.

thankyou for the report

i will continue to use mine in marinas where the current is iffy and sometimes way too high. my boat is not wired like a cruise ship.
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Old 16-04-2013, 06:31   #8
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The USCG report is gobbledygook to an engineer and it is impossible to know what they are talking about. Was it a 220V vessel? What does it mean "a ground developed" in another circuit? Without further information and diagrams it is hard to say what lesson should be learned from this.
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Old 16-04-2013, 06:37   #9
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Re: Power strip dangers

was , by chance, uscg referring to the fires in carnival lines ships, or were there other instigations causing the alleged research on part of uscg and their gobbledygook engineers with their gobbledygook wording.....
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Old 16-04-2013, 06:43   #10
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Report says the fires were on container ships. Who knows what kind of electrical system they had? How many US flagged container vessels are there in the world? I hardly ever see one.
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Old 16-04-2013, 06:43   #11
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Re: Power strip dangers

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Originally Posted by transmitterdan View Post
The USCG report is gobbledygook to an engineer and it is impossible to know what they are talking about. Was it a 220V vessel? What does it mean "a ground developed" in another circuit? Without further information and diagrams it is hard to say what lesson should be learned from this.
Exactly. And if there are "grounds developing" in other circuits there are problems way beyond any potential problems with a surge protector.
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Old 16-04-2013, 06:48   #12
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Re: Power strip dangers

so, guys, i am willing to take one for the crew..i use mine whenever i wish, usually in marinas where the pout[put is read on a meter to be 137volts....and when i need to use mpre than one outlet in my boat.
i can safely say i never smelled any stink from burning eletricity,nor has my ground fault thingie made any fuss about the circuitry.
my surge protector is mexican and it has ground and reverse polarity lights for alleged safe usage...i like that feature as i have had bad ground from marina in past...at la cruz marina. the strip helped me to find the cause and repair it before fires or stinky smell.
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Old 16-04-2013, 10:55   #13
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Re: Power strip dangers

Quote:
Originally Posted by goboatingnow View Post
this is the electrical gobbledi-gook thats is teh USCG report, as an EE I havent a clue what they mean.

surge protection typically has MOV devices that sit accross live and neutral, they crowbar them together briefly in a surge situation, how this could afect anything on a typical yacht is beyond my simple electronic brain.

Dave
Agreeing with the others, that report makes no sense.

All I can think of is that either there was a persistent overvoltage, or the MOV failed short, and in either case there was enough current to burn the sucker up, but not enough to trip a breaker or fuse.

My own power-bar warning; I've had a few of the molded ones heat up and start melting around the outlet when a higher-current appliance (eg heater, kettle) was plugged in and the contact was iffy. The cheap plastic power bars should be avoided in favour of the better ones with higher-grade sockets in a metal extrusion, if you need to run heavier AC loads.
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Old 18-04-2013, 12:24   #14
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Re: Power strip dangers

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Originally Posted by GLtrawler View Post
Because most SPDs interrupt only the hot conductor when a surge occurs.
Many believe that because advertising avidly promotes myths. Adjacent protectors do not work that way.

First, to work, a protector adjacent to electronics must either block or absorb surge energy. So view the numbers. If destructive surges are as much as hundreds of thousands of joules, then what do hundreds of joules in that protector do?

Grossly undersized. A protector part must disconnect while leaving the appliance connected to that surge. A thermal fuse (ie 1 amp) must disconnect protector parts as fast as possible. Otherwise a fire can result.

Sometimes that thermal fuse does not open fast enough. Then protector parts become a potential fire. Any smoke or burning inside a protector means it was on the verge of fire. That failure mode is a violation of MOV manufacturer specs.

Second, protectors are only designed for rare and short transients. Maybe a transient once every seven years. That transient being microseconds. Even fuses and circuit breaker takes millisecond to trip. Meaning a destructive surge does not cause circuit breakers or fuses to trip.

Third, what does that protector light report? It only reports one type of failure. A failure that says the thermal fuse (the other fuse) tripped to avert fire. A failure because the protector was grossly undersized.

Fourth, that Coast Guard report describes a type of failure that (to a protector) was electrically similar to an open neutral in homes. Causing an anomaly that the protector is not designed for. Apparently its thermal fuse did not open fast enough to avert the resulting fire.

If its light says a protector has failed, then the protector was grossly undersized. And was dependent on its last safety layer to avert a fire. A warning to the owner to not buy another one. Those fires should have everyone’s attention. Because those protectors do not perform as so many only assume.
 
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Old 18-04-2013, 12:40   #15
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Re: Power strip dangers

the report the op posted is fine n dandy in and for the kind of ship it was written about.
it is not relevant to any other kind of ship.
we are not sailing on ships, but in homes we have prepared for this work, or not...and we each takes our chances--

thankyou for the report.
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