Dual 30A/120V Shorepower Grounding

[GordMay]

How Stray Voltage Affects Multimeter Measurements
...and What You Can Do About It (Low Z V).

➥ http://support.fluke.com/find-sales/...01_ENG_B_W.PDF

➥ http://www.electricitymetering.com/c..._circuits).pdf

[Beausoleil]

Thanks for the hard work here - the forum can be a wonderful thing!

Originally Posted by CharlieJ

...
Cap'n Jon- The schematic indicates that the MMS2812 was wired in a dual in/dual out configuration. After reviewing the wiring Table 2-3 in the Magnum techman http://tinyurl.com/qay83w I have to question this decision as you have no 240 VAC loads, and you are not supplying the I/C with 120/240 VAC split phase. The internals of the I/C may be "expecting" two legs of split phase power but only "seeing" a single leg.

CharlieJ:

I don't see how the inverter can "expect to see" two legs of split phase power, but you never know. I wired it according to the tech manual - but an earlier version than your URL. The early version specifically adds an option very similar to the single in/single out scenario in table 2-3 on page 24 of your version of the manual. My version (which, admittedly, is rev 12-04 - probably outdated) says the preferred method of SI/SO is to tie Hot1 to Hot2 on the input side, and Hot1 to Hot2 on the output. The electrician who installed the unit did it without the jumpers - so I added them.


In the newer version of the manual, there is no mention of those jumpers. I'll try taking them out - I haven't done that since I modified the neutral buses that the electrician came up with...

Originally Posted by CharlieJ

Some final points:
1. You really need to hand over hand the as built wiring to ensure that the wiring diagram truly depicts what is reality.
2. Have you contacted Magnum Energy yet? I have had to talk to their technical support extensively on a problem that I had with an installation and I found them to be incredibly responsive and knowledgeable. If you need a point of contact, please contact me.
3. Finally, some problems are just too complex be solved in a forum atmosphere. One small omitted factoid can skew the entire logic tree. For example, if a high impedance DMM is used to check continutiy across a switch, the switch will test satisfactory. The fact that the switch had high resistance across the contacting surfaces would be masked by the characteristics of the DMM. This small ommission could direct the forum participants way down the wrong path. It is my opinion that your problem is complex enough so that a qualified electrician needs to be on site with the proper instrumentation in order to resolve it.

73-
Charlie

Point 1 - I'd love to, but you'd be appalled if you saw the actual as-builts which I finally received in January - after the work was finished in June/July and after our cruise started in September. They are simply worthless - they only show the wiring plans - where each circuit goes to physically in the boat and not how anything is wired up. I begged and pleaded for months, and a scan of a hand-drawn diagram is all I got.

Point 2 - I originally contacted Magnum in December, and tried some things their tech suggested. I got really busy on other projects and let this problem sit until now. Talked to Eldon - great guy. I started an e-mail to them, but lost the draft. I'll create another and send it to them. I even suggested that in a future model, they should support two independent input neutrals and two independent output neutrals when in pass-thru mode so they can really meet ABCY recommendations when installed on a boat...

Point 3 - Readily agree. My goal here was to see if anyone could see something I was missing - "can't see the forest for the trees" kinda thing...

I'll run this info past Magnum - perhaps the ultimate fix will have to be replacing the dual 30A 120V shorepower inlets with a single 50A split phase system with a single neutral bus.

Chala:

I mis-stated the breaker tripping - it's not the input breaker CB3 that's tripping, it's the internal triac (or whatever it's called) which actually switches the unit from pass-thru mode to invert mode. I should have said the unit kicks into invert mode.

All:

I have to sail from Port Canaveral, FL to Charleston or Beaufort, SC this weekend, so I'll revisit this problem next week when I have time. I'll just continue what I've been doing and run the genset lightly loaded until I figure this out...

Thanks for the support!

[Beausoleil]

I just re-tried the system while on the hard for the first time in months. I discharged the house bank (800Ah) down to 80% SOC, then, while connected to shorepower rather than the genset, I fired up the Magnum inverter/charger and the microwave (both on L2) and the Iota charger and water heater (both on L1). Total amp draw was 47 amps.

So that leads me to believe that the genset, when configured for 120/240VAC, is extremely sensitive to unbalanced loads between L1 and L2. Since it's an easy configuration changed to set it to only 120VAC 60Hz, I'll try that and report back.

Right now I've got my hands full dealing with the extreme weather we're having in central Florida at the moment, so it may be a few days before I report back...