# Control/Dimming Power and Dimmer Rack on Cruise Ship

Discussion in 'Lighting and Electrics' started by lighttech11, Dec 21, 2012.

1. ### lighttech11Member

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Hi there,

I'm working on replacing a dimmer rack system for theater on a cruise ship. I'm replacing a very old dimmer system with a new ETC Sensor 3 48 module installation rack.
Just so we're all on the same page, the new rack is 230V, and requires 3 hot phases, a neutral, and a ground. Standard, right?

Now, both from my own observations of the old dimmer rack on the ship, and from what the chief electrician on the ship is telling me, the ship does not actually distribute a neutral conductor. All it distributes is 3 phases of 220V and a ground.

And like I said, that is also what I observed from looking at the old dimmer racks. There are just 3 phases of 220V between each phase, and then a ground.

So, based off of what I've been taught and experienced, there are multiple things that are wrong with this as compared to 3-phase power on land, right?

On the ship I'm reading 220V between each hot phase
And i'm also reading 220V between hot phase and the ground.

Also not normal, right?

Can anyone explain this more? Anyone out there who is more familiar with cruise ship power? Or worked with or installed recent dimmer racks (preferably ETC Sensor) on a cruise ship?

I can't actually even be certain the feeder is true 3-phase. It's possible it's some form of transformed split-phase? I haven't been able to ask the chief electrician yet and I do not own a meter with the capabilities of measuring the sine waves.

I'm trying to see if it's possible to make things work just using the 3 phases and the ground as a neutral, but I don't know if that would work, be safe, or much less be to code.

Ideally, what I want for the new sensor rack is 220-230V three-phase 4-wire plus ground, where:
phase to neutral is 220V
phase to ground is 220V
and phase to phase is 380V
Correct?

I just want to check my work with others.

Any help, thoughts, or comments greatly appreciated. Thanks!

Also, just for info, the old dimmer racks are Artick Digilight 12 channel rackmount dimmers. About 18 years old, made in Italy.

Last edited: Dec 21, 2012
2. ### JDWell-Known Member

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Couple of things:
1) Are the cabins equipped with 115 volt outlets, or the European 220 volt outlets?
2) What are lamp voltages in the fixtures? Are they equipped with 230 volt lamps?

The 220 Hot-to-hot AND 220 Hot to Ground sounds like a misread. Although if you are reading a floating delta, it can be like a dog chasing it's tail with regards to measurements to ground. Obviously, it is possible that the ship uses the European model of theater (220 volt) as compared to the US (120 volt) model. Very gray area as to jurisdiction for electrical code. My understanding is that cruise ships have to meet code in the countries they make port at. I am NOT an expert on maritime law, so I may be flat out wrong about that.

In theory, connectors such as the 2P&G should have a "hot" contact, and a return contact (neutral) at or near ground potential, as well as a ground contact. Having two "hots" is not allowed for the standard 20 amp 2P&G connector. (If that's what is in use.) So, one would not think that the dimmer/load circuit is suspended between two hots, even at 220 volts. One would Think.....
As for using the ground as your neutral, it is clearly against code in most countries that have an electrical code. I don't think this is the case. Something is being overlooked.
One other thing to check out- What frequency is the power at? 50 or 60 Hz.

Last edited: Dec 21, 2012
3. ### lighttech11Member

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The cabins are equipped with both 110V AND 220V outlets (for "convenience").

frequency is 60HZ

Okay, I retook my readings, and I found approximately 226V between each hot leg.
I then found that I actually am getting 226V between hot and ground on only two legs. So:
L1-ground: 226V
L2-ground: 0V (approximately)
L3-ground: 226V

even weirder? or no?

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I'm going to go with ... "or no".

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5. ### JDWell-Known Member

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Exactly. So, the dimmers are wired Hot-to-hot, and the lamps are 220 volts. Make sure you new rack is configured properly and obeys the "no smoking" sign.

Last edited: Dec 21, 2012
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6. ### FooterSenior TeamSenior TeamPremium Member

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7. ### lighttech11Member

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Thanks everyone! For some reason I kept telling myself "no delta is too weird to be used on the ship" (as I am not nearly as familiar with delta as I am with wye, since it is not found in most theaters on land). It's quite obvious to me now what is going on. The ship is indeed generating 3 phase delta corner grounded. Which, unfortunately, is not compatible with our new rack (it's just the standard 3 phase wye sensor rack. Also unfortunately I was not part of the ordering process, but we shall have to exchange for a delta rack somehow. Thanks for everyone's help!

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Delta is a great power solution for ships for several reasons. Don't forget that the worst enemy of a ship [sitting in a giant pool of water] is fire and therefore electrical safety is part of that.

Most ships now manufactured have multiple gas-fired electrical generators to run all the electrical gear and propulsion. Screws have been replaced by or supplemented with electric drive pods that are both prime movers and can rotate under the ship to dock them without use of tugs. It's a pretty cool setup.

- Any single short to the ship's hull does not take down a power grid since the power system is floating. In fact, it is not uncommon for several of the power systems on the ship to have a nagging short to hull now and then.

- If the hull was to be used as a return path [neutral or ground bonded to neutral], this would promote and accelerate electrolysis thereby causing the hull to rust and decay faster. So those lingering occasional phase shorts should be resolved.

Most ships are running 230V delta, but you have to ask to make sure. There are a number of ships that have a delta to wye transformer specifically for the performance spaces. This was done because of the increased need to provide power for standard 120V theatrical products. Do ask about that as well when doing new installs or refits.

Yes, this is all confusing as there is no standard build for ships.

Good luck,

David

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9. ### derekleffewResident CurmudgeonSenior TeamPremium Member

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I see what you did there.

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