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Replacing 2 50 amp shore power with single 100 amp

Discussion in 'Technical Discussion' started by Jdow, Jan 17, 2019.

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  1. Jdow

    Jdow New Member

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    I have a client that is a bit tired of dragging 2 shore power cords down the dock from his Viking. The cable masters for each are on opposite sides of the cockpit. I want to explore the idea of installing one cm8, with a single 100 amp cord on the starboard side, then split back into 2 50’s in the engine room at the junction box currently there. Any thoughts?
  2. captholli

    captholli Senior Member

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    I assume its a Viking SF? It depends on what electrical equipment is already installed in the E.R. . Mid 2000 Vikings have a Atlas auto former that both 50 amp inputs go to for phase polarity and boost and then a secondary backup shielded buck boost x-former if your Atlas PLC dies. Both of these units aboard are set up for two 50 amp inputs only. If you have the described Atlas than I don't think it'll accept one 100 amp input as its KVA isn't rated for that You would also have to remove the two existing cable masters and install one for the 100 amp cord and the 100 amp cable master is a beast size wise with the larger cable spool bucket etc. Seems to me that if your willing to remove the smaller x-formers and go with one larger 20 kva or so unit than it would be doable depending on your clients $$ pain threshold vs dragging two cable master assisted cords out. Personally I'd rather have the option of two fifties if I had to run critical services off of just one cord in an emergency.
  3. Pascal

    Pascal Senior Member

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    What size boat? He s not going find many slips under say 80’ with 100amp service so he will have to carry the heavy and expensive 50 to 100 box...
  4. Jdow

    Jdow New Member

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    It is a 65 enclosed bridge sf, that spends its time between Newport, mountauk, and Nantucket. Good points, and I will have to investigate further. My thought was to run the 100 amp cord into a junction box, split it back to 2 50’s, and leave everything else as it was.
  5. Capt Ralph

    Capt Ralph Senior Member

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    Have you priced out 100A cords? 4 x 4AWG.
    Heavy and expensive.
    Most 50A cable masters can not be adapted for this cable.
    Heavy expense to buy a 100A cable Master.

    IMHO, cheaper and better to tip (well) the dock service to drag the light 50A cable if he can not do it himself.
  6. Jdow

    Jdow New Member

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    Yes I have, the boat is undergoing a 500k refit/paint. He either wants 2 new cm7’s, with new 75-100’ 50 amp cords on one side of the boat, or the single 100.
  7. chesapeake46

    chesapeake46 Senior Member

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    THAT'S the answer.....
  8. captholli

    captholli Senior Member

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    First step is determining what isolation system that's aboard. If you have the Atlas in the aft Starb. corner of the E.R. and the secondary Acme x-former aft port. If your not equipped this way than maybe its a easier deal for you. I don't think that's its as strait fwd. as you believe by running a 100 amp svc into the exiting shore J -box and using the existing circuits / wiring from that point fwd. if you have this primary and secondary x-former isolation system. Does your J-box have a shore power contactor in it with auxiliary contacts for your secondary system Acme bump boost? The 2004 65 Viking I was involved with was optioned to the max from New Gretna and I believe the Atlas PLC controlled auto former was an option and an expensive one at that.
  9. Jdow

    Jdow New Member

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    I’ll have to get back in there and look at it better. So far I do know that each shore power cord comes into the cable master, then out to 50 amp 2 pole breakers. Each side it’s own. I’ll look into it further to where it goes from there and what transformers may be used. The boat is a 2001
  10. Jdow

    Jdow New Member

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    Just a question, not trying to sound argumentative, but wouldn’t this essentially be the same as using a splitter at a 100 amp pole to 2 50 amp cords? Just the 50’s will still be in the boat. I know just enough about a/c voltage to be dangerous so bear with me and I appreciate the replies.
  11. captholli

    captholli Senior Member

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    jdow,
    I'm a glass half full type of guy and didn't mean to sound negative. I hope that you can achieve the desired outcome for your client . Outside of armchair marine engineers like myself , you need to consult a qualified marine electrician and preferably one who knows Vikings systems well.
    So in theory yes, you can convert your two 50 amp cord system to one 100 amp. The only issue that comes to mind would be polarity on L-1 L-2 if you retained the split buss switchboard with one 100 amp service . Right now you have two 50 amp svc. feeding your main electrical switchboard that has a split buss arrangement. If you blow a shore breaker for one of the cords on the dock than you'll still have power on half of the switch board through the remaining energized cord. Each of your 50 amp cords will be going through a isolation transformer and have galvanic isolators on each along with circuit protection (Breakers) on the primary and secondary side of your isolation transformers. If this is the setup that you have than you would be required to remove the two small 10 kva isolation transformers and replace them with one x-former rated for 100 amps or 22 kva @ 240 volts and modify your switchboard for a single buss system or purchase a smart isolation transformer that has sensing taps for polarity. If you have the atlas setup with the Acme secondary isolation transformer than its going to be a bit more involved equipment removal and wiring wise. It shouldn't be more than a days labor rate for a qualified marine electrician to give you the correct answers for this scenario & it'll be $$ well spent .
  12. Capt J

    Capt J Senior Member

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    The 2 50s are on opposite sides of the boat for balance. Between the weight of the cord, the drum, the glenndenning and all of that stuff is probably 150 lbs, if you move it to the other side it's going to create a list, probably 3" list that I wouldn't do. Honestly there is very little to gain. 100 amp cable is very expensive, dockside service is limited and 100 amp stuff is very expensive compared to 50 amp. Quite honestly I'd leave everything well enough alone.
  13. RER

    RER Senior Member

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    As someone who has cruised extensively with 100' of 100 amp shore power cable on a cablemaster, I would rather deal with two 50 amp cords.
  14. Jdow

    Jdow New Member

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    I get what guys are saying, I’m going to have to weigh it out and propose the options.
    Do you seriously think 150 lbs moved to one side is going to cause a 3” list on a 65’ long, 19.5’ wide sport fish???? Thats less than the difference between a full and empty fridge????
    The larger of the 2 gensets has a bench and 2 tool boxes on it. While it always best to balance as much as you can 150 lbs on a 100,000 lb boat I can’t see making a difference.
  15. Capt J

    Capt J Senior Member

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    Absolutely, it's a 300 lb swing from one extreme side of the beam to the other side of the beam, and the closer to the cockpit you get the more weight off center tends to make a boat list. Stand on one side of the cockpit and walk to the other and have someone watch the waterline. I just don't understand why anyone would want a 100 amp cord to replace 2-50's......100 amp cords are extremely heavy (compared to 50's) and a bear to drag around, very limited receptacles to plug them into, and very expensive for ends, splitters, etc.
  16. olderboater

    olderboater Senior Member

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    If you figured out how to successfully do this, it's still a lot of work, a lot of expense. for mostly nothing. Occasionally you'd benefit and probably more often it would be a negative. I'd make major changes only when I was sure of significant advantages without disadvantages. This is not one of those situations.
  17. cnvsback

    cnvsback Member

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    I have a client who's 75 Hatteras has been retro fitted with a similar shore power setup. From Hatteras factory all 75's came standard with 2x 50a shore cords and Glendenning electric reels. The particular one I'm speaking of has been fitted with a single phase 100a shore power inlet, Charles C isolation transformer, the associated breakers, transfer switches and wiring at the main distribution panel. The installation is done very nicely and to ABYC electrical standards. If I remember seeing the invoice correctly $30-35k when installed in 2009. As far as the 50a system goes that has been left in place and the boat can accept either single 100a or dual 50a services you just need to correctly source select at the main distribution panel.

    The 75' came in 4/5SR layouts, when 8 guests or more are onboard its not difficult to find the threshold of the 50a system on a hot Florida summer night in 85+/- degree cooling water. Seven direct expansion AC units don't help the cause(this boat has a additional 48k btu flybridge air). The previous owner of the boat was tired of resetting breakers in the middle of the night with a full guest load on board and retro fitted the single phase 100a service. For this boat I feel the system is a good addition being as it is a dockside floating condo with minimal generator usage. It also gives flexibility when moving marina to marina. If they have an available 100a service, great. If not get the 50a's out and load manage. Theres a huge locker on the swim step where the 100a cord is accessible with relative ease.

    See main switchboard wiring schematic below.

    Attached Files:

  18. Jdow

    Jdow New Member

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    Thank you, the boat has 2, iso boost 50 transformers. Some more discussion with the client is needed before going further