Hi guys. Merry Christmas!
My AC units were delivered recently, and that's got me thinking about electrical things. I've got an isolation transformer that's wired for 240 --> 240, so only the two hots and ground come aboard. The ground goes to the transformer case. Two hots and a neutral come out of the transformer to the distribution panel...no ground. All of the OE wiring uses two prong outlets; no grounds.
Do those of you with transformers have grounded plugs on your boat? If so, where is 'earth' for your floating electrical system?
One reason I ask is because every generator I've owned has 3-prong plugs. And that got me thinking that even on power systems not connected to the grid, there must be an 'earth' somewhere.
Thx
Q
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12-24-2017 08:28 AM #1Senior Member
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Isolation transform = no grounded plugs?
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Re: Isolation transform = no grounded plugs?
I may be wrong and I can't be sure without pulling out my schematics but I believe the neutral and ground are tied together in the panel. The case on the transformer is also tied to ground and the ground in the panel is tied to the bonding system. If you want, I could look it up next time I'm at the boat.
Sky Cheney
1985 53EDMY, Hull #CN759, "Rebecca"
ELYC on White Lake--Montague, MI
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12-24-2017 09:42 AM #3Senior Member
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Re: Isolation transform = no grounded plugs?
Hmmmm. Interesting. Let's see how others chime in.
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12-24-2017 09:52 AM #4
Re: Isolation transform = no grounded plugs?
Being a metal boat novice I'm not sure how things are supposed to be on it but on the hatts there is no earth ground when running. Shore power brings an earth ground to the isolation transformers and connects it to the earth but the boats systems have neutral and ground connected.
Scott
41C117 "Hattatude"
Port Canaveral Florida.
Marine Electronics and Electrical Products Distributor.
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Re: Isolation transform = no grounded plugs?
Ground and neutral should only be tied at the source, i think it s an ABYC standard. That would be thru shorepower, at the generator or at the inverter. This is why marine inverters have circuitry to tie G and N when in inverter mode and relase it in charging or pass thru mode.
Pascal
Miami, FL
1970 53 MY #325 Cummins 6CTAs
2014 26' gaff rigged sloop
2007 Sandbarhopper 13
12' Westphal Cat boat
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12-24-2017 05:51 PM #6Senior Member
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Re: Isolation transform = no grounded plugs?
This article will help....I think the ABYC has updated slightly since he wrote it (see GFP comment below). It also references the ABYC. Notice there is a difference between Isolation and Polarization wiring. http://qualitymarineservices.net/Tra...%2010-2006.pdf
Charles has the ABYC diagrams too: http://www.charlesindustries.com/mar...l/38kvaISO.pdf
Please note on page 6 there is a typo in the message. Method 1 and 2 are different than 3 and 4 (latter use Ground Fault Protetction)Last edited by krush; 12-24-2017 at 06:04 PM.
FTFD... i drive a slow 1968 41c381
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Re: Isolation transform = no grounded plugs?
Great article
Thanks,
Tony
2008 Cheoy Lee Bravo 78 "Bella Sophia"
1989 78' Hatteras CPMY #311 "Bella Sophia" (sold)
2007 Everglades 290cc “Bada Bing” (sold)
2006 Advanced Outdoors 28cc (sold)
2003 Melges 24 "Bada Bing" (sold)
2023 HCB 42 “Bada Bing”
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12-25-2017 06:54 PM #8
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Re: Isolation transform = no grounded plugs?
Mine was a 1989 65MY. Here is the transformer wiring diagram. I would be surprised if yours wasn’t the same. By the way this is the diagram to flip the transformers to allow for voltage boost.
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12-26-2017 06:34 PM #10Senior Member
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Re: Isolation transform = no grounded plugs?
Thx krush. Great article.