Post-Conception Disaster: what you learned & will change

[KevinNM]

I'm not an electrician so I am going by what I was told, but marine circuits are wired different, instead of the wires being 120V and 0V, they instead provide 60V on both wires at the same time. While most surge protectors work by shunting the hot wire to ground, but since the marine power system doesn't have a hot wire they are still receiving power.

I was on a big cruise ship and they confiscated my power strip for the duration of the cruise after the x-ray spotted it in my luggage They said it could cause a fire. I didn’t ask for details but they didn’t get to be big by needlessly annoying customers, so I assume there is something to that.

 

[ontdiver]

I was on a big cruise ship and they confiscated my power strip for the duration of the cruise after the x-ray spotted it in my luggage They said it could cause a fire. I didn’t ask for details but they didn’t get to be big by needlessly annoying customers, so I assume there is something to that.

I believe the concern is that the power strip presents an unmanageable risk as a fire hazard. For this reason, some LOB operators do not allow in room camera/dive light recharging.

 

[danddmiller1]

View attachment 645054 I

Any photos

 

[kelemvor]

View attachment 645054 I

Any photos

The photo you posted doesn't work.

 

[Wookie]

I'm not an electrician so I am going by what I was told, but marine circuits are wired different, instead of the wires being 120V and 0V, they instead provide 60V on both wires at the same time. While most surge protectors work by shunting the hot wire to ground, but since the marine power system doesn't have a hot wire they are still receiving power.

No. Marine 120V and house 120V are wired identically with one small difference. There is no safety ground on a marine circuit. Before the advent of electronics that REQUIRE a ground, circuits were 2 wire, hot and neutral. Notice I didn't say common. Neutral wires back to the center tap of a wye wound 3 phase generator. That's why even on a single phase generator, you have 2 hot legs for 240V, but you have a neutral instead of a common leg. You can make a ground if you want, but it's dangerous for swimmers (if something fails and goes to ground, it energizes the ground in the water and in fresh water, kills in about a 20 foot radius). In sea water, the kill radius is far smaller, but still exists. So dive boats don't have a safety ground, they "fake" the ground by wiring it back to neutral, but that does not provide safety in the event that a piece of equipment fails and grounds the case.

So how do you protect the passengers from faulty electrical equipment? You physically ground the equipment to the hull in the event of a metal hull, and run a grounding loop around a wood or glass boat. The grounding loop connects to all of the equipment that requires a ground, and to a bronze shoe in the hull. Once again with the stray current and divers in the water. I can share the ABYC proper wiring diagram for modern vessels if folks are interested, but I'd bet a grand that a boat built in the 80's was not built to modern standards as far as wiring goes. Especially as the USCG doesn't require the upgrade.

 

[dberry]

Thank you for that clear and cogent explanation!

 

[Wookie]

Thank you for that clear and cogent explanation!

You're welcome. Seemed clear as mud to me if you don't understand the terms, but I'm happy to share.

 

[Open Ocean Diver]

Ground wires normally tie back to the panel at the neutral point, so grounds wont carry any current in normal operation, but when a fault happens ie hot wire shorts to ground it completes a circuit and trips a breaker, in ungrounded system you need a GFI to detect unbalanced currents in order to trip the circuit.

 

[araviele]

I’m curious what the plan is for Covid testing to return to US from LOB. Can they test on board? Do you need extra days on land for testing and results?

went on the TCI Aggressor late March. The Covid Antigen test was conducted on-board when we arrived in port on Friday. Everyone was tested and all were negative. Each of us received a letter with our results for our flight back to the USA in about 90 minutes. About 16 passengers were $75 dollars poorer.

 

[Wookie]

The coast guard came out with a new policy. I heard from a live aboard that is considered high risk. This will maybe prevent the CG from allowing another tragedy to happen. https://www.dco.uscg.mil/Portals/9/...NCE FOR HIGH RISK SMALL PASSENGER VESSELS.pdf