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Old 29-07-2020, 11:27   #1
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Dual 120/240 shore power, Part 2

First, thanks to all for the comments on the first thread. After crawling throw the bowels of son in laws boat have discovered a few things. Some I mentioned on the previous thread but for clarity will cover it all here.

1. Boat is a 2004 56' Viking with dual redundant (IE use one at a time to power all systems) 21 kW generators. AC panel has switches for Shore Power 1 & 2, Gen 1 & 2, and loads divided into two banks.

2. Boat came with one 50 amp 120/240 shore power cord hard wired on a reel. The Hubbell connector has three prongs: one flat and two L shaped with the L turned out. Connector also has a metal collar around the plug.

3. In the bottom of the reel cabinet found a 50 amp 120/240 socket which I determined feeds Shore Power 2 to the panel. The socket has the same configuration as the plug on the Shore 1 reel cord.

4. Wiring as follows: Shore power cords to sockets on the boat. Sockets on the boat to circuit breaker box. Box to Charles isolation transformer. Transformer to Electric Panel

5. Bought a new 120/240 shore power cord, connected to the outlet and plugged into the dock. On the panel it only showed 107V on L1, 108V on L2. Shore 1 shows 120V on each leg. Checked voltage on the dock and at the boat end of the new SP 2 cable and it measures 120V on both legs.

6. Disassembled the socket on the boat to check for corrosion which was moderate BUT the shore power sockets on the boat are not wired how I expected. My understanding for the correct wiring:

The two prongs or sockets on the sockets or plugs that are L shaped are the two hot wires L1 and L2, correctly Red and Black wires. The flat blade is the White neutral wire. The green ground wire connects to the metal outer ring or the flat metal ground on the side of the plugs or connectors.

BUT inside both sockets on the boat that receive the shore power are wired:

Black from socket L1
White from socket L2
Green to the metal ground around the connector

AND no wire or connection at all to the socket that receives the flat blade for the White/Neutral wire. So no connection at all between the W/Neutral in the shore power cord from the dock to the boat.

I looked inside the breaker box where the wires lead directly from the sockets in the cockpit. Two sets of double breakers, one pair for SP1, one pair for SP2. Both show a white and black pair coming in and out. From there the wires pass through conduits and bulkheads to the electric panel. I opened the panel and and the double SP1 and SP2 breakers inside the panel have a red and black pair in and out of the breaker, then feeding the load breakers inside the panel.

My questions, in no particular order.

1. If no wires are connected from the boat to the White neutral on the dock doesn't that mean that the safety ground is carrying the current from the dock to the boat?

2. The SP1 hard wired system seems to be working fine, voltage is good although the breakers on the dock do get hot. Not sure if that is because we are drawing a heavy load or due to the weird wiring.

3. Is it possible that this is correct due to the Isolation Transformer in the system?

4. Is this setup completely wrong and we're going to set the boat on fire.
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Old 29-07-2020, 11:38   #2
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Re: Dual 120/240 shore power, Part 2

Can't answer the other questions but if you have an isolation transformer and 240V shorepower connection the neutral is not used. In US split phase current only flows on the neutral when you are tapping one of the 120V hots. In this case you aren't. The only connection between the shorepower and your boat is the isolation transformer which is using only using the 240V circuit (L1 to L2).



Related this means you can still get split phase circuits in the boat when connecting to European shorepower. It will be 115/230 @ 50 Hz not 120/240V @ 60 Hz but you can keep the dual voltage setup.

As for the voltage sag depending on the wiring gauge and length that isn't that unexpected. I would check the voltage at both the isolation transformer inputs and outputs to verify.
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Old 29-07-2020, 11:46   #3
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Re: Dual 120/240 shore power, Part 2

Actually I realized that diagram may be confusing because it is a slightly different scenario (240V primary to only 120V secondary).

Grabbed this from charles marine isolation transformer manual



This more accurately reflects what you described. 240V primary, 120V/240V split phase secondary.

Note the neutral wire on shore power disconnected. Also note the grounding setup. Shorepower grounds to isolation transformer shield only. The boat AC circuit ground wire joins to neutral at the isolation transformer secondary. There is no direct connection between boat AC circuit ground and shorepower ground.
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Old 29-07-2020, 12:11   #4
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Re: Dual 120/240 shore power, Part 2

Installation manual says: The green grounding wire from the shore is connected to the shore power inlet shell which is insulated from
metal-hulled boats. Do not connect the shore green wire to the boat ground.

Do you know if it is a 100 amp transformer?
http://www.charlesindustries.com/mar...r24i-1_pr4.pdf
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Old 29-07-2020, 12:27   #5
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Re: Dual 120/240 shore power, Part 2

On closer look the manual describes two complying methods, one brings the shore green wire to a shield on the case of the transformer, the second terminates it at the connector. If using method two it says you need gfci breakers before the transformer
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Old 29-07-2020, 12:38   #6
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Re: Dual 120/240 shore power, Part 2

Quote:
Originally Posted by skipmac View Post
First, thanks to all for the comments on the first thread. After crawling throw the bowels of son in laws boat have discovered a few things. Some I mentioned on the previous thread but for clarity will cover it all here.

1. Boat is a 2004 56' Viking with dual redundant (IE use one at a time to power all systems) 21 kW generators. AC panel has switches for Shore Power 1 & 2, Gen 1 & 2, and loads divided into two banks.

2. Boat came with one 50 amp 120/240 shore power cord hard wired on a reel. The Hubbell connector has three prongs: one flat and two L shaped with the L turned out. Connector also has a metal collar around the plug.

3. In the bottom of the reel cabinet found a 50 amp 120/240 socket which I determined feeds Shore Power 2 to the panel. The socket has the same configuration as the plug on the Shore 1 reel cord.

4. Wiring as follows: Shore power cords to sockets on the boat. Sockets on the boat to circuit breaker box. Box to Charles isolation transformer. Transformer to Electric Panel

5. Bought a new 120/240 shore power cord, connected to the outlet and plugged into the dock. On the panel it only showed 107V on L1, 108V on L2. Shore 1 shows 120V on each leg. Checked voltage on the dock and at the boat end of the new SP 2 cable and it measures 120V on both legs.

6. Disassembled the socket on the boat to check for corrosion which was moderate BUT the shore power sockets on the boat are not wired how I expected. My understanding for the correct wiring:

The two prongs or sockets on the sockets or plugs that are L shaped are the two hot wires L1 and L2, correctly Red and Black wires. The flat blade is the White neutral wire. The green ground wire connects to the metal outer ring or the flat metal ground on the side of the plugs or connectors.

BUT inside both sockets on the boat that receive the shore power are wired:

Black from socket L1
White from socket L2
Green to the metal ground around the connector

AND no wire or connection at all to the socket that receives the flat blade for the White/Neutral wire. So no connection at all between the W/Neutral in the shore power cord from the dock to the boat.

I looked inside the breaker box where the wires lead directly from the sockets in the cockpit. Two sets of double breakers, one pair for SP1, one pair for SP2. Both show a white and black pair coming in and out. From there the wires pass through conduits and bulkheads to the electric panel. I opened the panel and and the double SP1 and SP2 breakers inside the panel have a red and black pair in and out of the breaker, then feeding the load breakers inside the panel.

My questions, in no particular order.

1. If no wires are connected from the boat to the White neutral on the dock doesn't that mean that the safety ground is carrying the current from the dock to the boat?

2. The SP1 hard wired system seems to be working fine, voltage is good although the breakers on the dock do get hot. Not sure if that is because we are drawing a heavy load or due to the weird wiring.

3. Is it possible that this is correct due to the Isolation Transformer in the system?

4. Is this setup completely wrong and we're going to set the boat on fire.
You don’t need the Neutral if you just take the 240V to feed a transformer, so that part is done correctly.

What is not clear to me: do both shore power connections go through their own breakers and then to the same isolation transformer? How are they connected at that transformer? I can imagine two parallel primary windings but then L1 and L2 still need to be at same side or else the two fields cancel each other.

Also, where are those voltage readings coming from? Surely there is an electrical diagram for the boat?
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Old 29-07-2020, 12:47   #7
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Re: Dual 120/240 shore power, Part 2

Thanks guys. We're in the boondocks in Maine with occasional, intermittent and unreliable connections so help from the forum is great.

I had suspected the isolation transformer had something to do with the situation and further could not imagine Viking would do it wrong. So seems like the wiring is all good as far as I have traced it. Now just need to figure out why the voltage drop on SP 2. I'll finish cleaning all the connections on the socket and see if that helps. If not will move on to the isolation transformer. If that doesn't solve it we'll have to start taking stuff apart to get to the other bits.
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Old 29-07-2020, 13:00   #8
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Re: Dual 120/240 shore power, Part 2

The voltage mystery may be due to the fact that it can also be wired as a 104/208 transformer. The manual shows the different configurations. I am confused about this statement: I looked inside the breaker box where the wires lead directly from the sockets in the cockpit. Two sets of double breakers, one pair for SP1, one pair for SP2. Both show a white and black pair coming in and out. From there the wires pass through conduits and bulkheads to the electric panel. I opened the panel and and the double SP1 and SP2 breakers inside the panel have a red and black pair in and out of the breaker, then feeding the load breakers inside the panel. because after the breaker box is the transformer right? To verify polarity you would connect both cords with the breakers off then check for current between the the two incoming white wires and between the two incoming black wires (there should be none). If there is current you will need to reverse one of the pairs. So as it stands you maybe could try use that second cord but would need to verify polarity first. This two cord system is not idiot proof.
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Old 29-07-2020, 13:03   #9
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Re: Dual 120/240 shore power, Part 2

The question is where is the panel voltage reading from? I thought it was from after the transformer. Another possibility is that the breaker in the off position can sometimes still give a voltage reading (salt air?)
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Old 29-07-2020, 13:25   #10
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Re: Dual 120/240 shore power, Part 2

One other thing that is not clear is do you have two isolation transformers (one for each shore power connection)? To my knowledge the largest isolation trans made by charles is 12 KW (240V 50A).

Is there only one iso transformer and both shore power outlets are connected to it? If so then that explains a lot but it also means the boat doesn't have 240V 100A service.
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Old 29-07-2020, 14:58   #11
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Re: Dual 120/240 shore power, Part 2

Quote:
Originally Posted by Statistical View Post
One other thing that is not clear is do you have two isolation transformers (one for each shore power connection)? To my knowledge the largest isolation trans made by charles is 12 KW (240V 50A).

Is there only one iso transformer and both shore power outlets are connected to it? If so then that explains a lot but it also means the boat doesn't have 240V 100A service.
They made a 100 amp:
https://www.windlass-anchor.com/Char...20-p/26081.htm
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Old 29-07-2020, 17:04   #12
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Re: Dual 120/240 shore power, Part 2

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Originally Posted by s/v Jedi View Post
You don’t need the Neutral if you just take the 240V to feed a transformer, so that part is done correctly.

What is not clear to me: do both shore power connections go through their own breakers and then to the same isolation transformer? How are they connected at that transformer? I can imagine two parallel primary windings but then L1 and L2 still need to be at same side or else the two fields cancel each other.

Also, where are those voltage readings coming from? Surely there is an electrical diagram for the boat?
Thanks. That makes it unanimous on the point about the Neutral.

Regarding the rest, I have only traced the wiring from the two shore power sockets on the boat, to the two double breakers. I stopped there to figure out the issue with the ground and neutral but I can see the cables out of the breaker box go into a large conduit. The wires into the Charles Marine isolation transformer are also inside a conduit so can't see what's going in.

Next step is to see if I can see inside the transformer case or get a model for the transformer to see what's happening there.

Will report back when I get more info.
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Old 29-07-2020, 17:31   #13
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Re: Dual 120/240 shore power, Part 2

Quote:
Originally Posted by Statistical View Post
One other thing that is not clear is do you have two isolation transformers (one for each shore power connection)? To my knowledge the largest isolation trans made by charles is 12 KW (240V 50A).

Is there only one iso transformer and both shore power outlets are connected to it? If so then that explains a lot but it also means the boat doesn't have 240V 100A service.
First quick look I only saw one transformer. Could be another one tucked away in a corner. Will be working on the next phase tomorrow but we won't be back at a dock for a few days to do a real world trial on the shore power systems.
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Old 29-07-2020, 17:35   #14
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Re: Dual 120/240 shore power, Part 2

Quote:
Originally Posted by Thumbs Up View Post
The question is where is the panel voltage reading from? I thought it was from after the transformer. Another possibility is that the breaker in the off position can sometimes still give a voltage reading (salt air?)
One V meter on the panel but can switch to read L1 or L2 and switch from SP1 or SP2 so separately reads all four hot legs.

Only reads voltage when the breaker is on for that leg. At some point if I don't track it down elsewhere I'll check voltage on the input side of the breaker vs output just to see.
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Old 29-07-2020, 17:42   #15
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Re: Dual 120/240 shore power, Part 2

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Originally Posted by skipmac View Post
First quick look I only saw one transformer. Could be another one tucked away in a corner. Will be working on the next phase tomorrow but we won't be back at a dock for a few days to do a real world trial on the shore power systems.
As Thumbs Up corrected me they use to make a 100A (24 KW) isolation transformer. It isn't on the website anymore (I assume they stopped producing it). So that likely is what you have but if you can get the model number off it that will confirm it.

I would use a multimeter to check the voltage between L1 and L2 on both sides of the transformer (primary and secondary). That should clear up a lot and if there is an issue determine if it is before or after the transformer.
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