NEMA 2000 with two power sources

Discussion in 'Electrical Systems' started by fallguy, Jul 26, 2021.

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  1. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    So, CZone uses NEMA for switch control interfacing (sci) to the COI. I have two 8 pack scis on the network and one digital switch box (dsb).

    The Furuno instrument display FI-70 is powered only via the NEMA 2000 network and the damn thing turns on with the network I use for switch control. I don't want an auxilary display to power up on its own. So, this means my NEMA backbone needs two separate power sources. One for the COI/dc distribution just fused off the battery switch and another one switched at the helm which can also turn on selected helm devices.

    so, here is what I did...

    I set the second NEMA power source up, but the COI became unstable and would kickout after a minute or so.

    A helpful techie told me to run two terminators on each end and one isolater, but failed to realize this was going to result in a gender change. The system works, but there is no connection between the coi and mfds, so it doesn't really work right.

    I am now wondering if the only problem was using the shielding from separate sources as Furuno has a warning against grounding multiple NEMA power shields.

    I plan to go retry it in a bit and remove the shielding from the added nema power cable. It was like 100F+ out there a bit ago.

    Anyone have any other ideas?

    Can I connect two ends of a NEMA via a drop on each one? Thinkin the techie was wrong. I'd rather not buy a gender changer if it won't work anyhow.

    I will update the post if the shield change resolves the issue.
     
    fallguy, Jul 26, 2021
    #1
  2. fallguy
    Joined: Dec 2016
    Posts: 7,632
    Likes: 1,684, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    So, I removed the shielding and put the NEMA back together without all the resistors and it still crashed the COI.

    <sigh>

    Now, I decided to pull the other device (Furuno tzt12f off the fuse block as it also has ground shields). The network is still setup as one network with two powers and an isolation. The coi seems to be stable. Perhaps this means I need a nema only distribution.

    So, I turned on only the Furuno tzt and it appears to stay on without the other side of the nema powered up. I think this is a ground loop problem.
     
    fallguy, Jul 26, 2021
    #2
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