ELCIs and galvanic isolator

[CaptFrankM]

I am going through a major refit and I just got the boat back in the water. The boat is a 1978 Morgan ketch with some significant PO "upgrades." I think I have removed most of the upgrades, but there is still a significant amount of original A/C wiring.

Before starting the refit, I had a survey done. Two of the things that the surveyor suggested were the addition of ELCI breakers on the shorepower inlets and the addition of either an isolation transformer or a galvanic isolator. Also as part of the upgrade, I added a NextGen 50 amp A/C generator.

I have two shore power connections. One feeds the house loads, which consist of a Mastervolt battery charger, a water heater, a Mermaid HVAC unit and a Xantrex inverter. The inverter powers all of the boat's sockets, but no other loads. The other connection only feeds a Cruisair reverse cycle HVAC.

In the old system, each shorepower line went to a dedicated 30 amp breaker, then to individual breakers. Because I added the generator, I added a Blue Sea three position selector switch (Shore-Off-Generator). From the selector switch, I now have two 30 amp ELCI breakers. These replaced the dedicated 30 amp breakers in each shorepower line, although they can now be fed by the two shorepower lines, or the generator.

In addition, I added a Zinc Saver 60 with a separate monitor unit. The ground lines for the two shore power connections route to one side of the Zinc Saver, then the ground lines split out again and run to a single point buss. All ground lines, including the generator, attach to this bus, so they should all be at nominally the same potential.

The monitor unit for the GI has two lines for each of the two shore power connections - one hot and one neutral. I believe that these are all hooked up correctly.

The neutral lines for each ELCI run together to a single neutral buss, to which the neutral lines for all appliances are connected. This ties the neutral for the Cruisair HVAC unit to the neutrals for all of the other house loads.

I am in a slip with a single 50 amp breaker and connector. From that connector, i have a Marinco 50 amp to dual 30 amp connectors. I then have the two 50 foot 30 amp shore power lines.

I have finally gotten all of this installed and, to the best of my knowledge, hooked up correctly. However, both of the ELCI breakers trip open immediately, when I try to shut them.

I believe the Galvanic Isolater is working correctly. It has a 3 light readout for reverse polarity, ground wire and isolator and all three lights are green.

I have not tried to use the generator yet. I want to make sure that the rest of the system is working before adding that wrinkle. One of the issues with the generator is that the ground and the neutral come off the same lug, so that they are interconnected.

I have read what I can about ELCI breakers, but I haven't found anything that mirrors this particular set up. I have read that the neutral and the ground connections on the ELCI load side sould not be connected together, but I haven't seen anything about them being connected upstream of the ELCIs, as is the case with my generator. I also understand that some chargers and inverters do something similar, tieing the chassis ground to the negative bus on the DC side, which is also connected to the A/C ground system in some cases.

My immediate thought is that, because I am running the neutral for the Cruisair HVAC to the same buss as all of the other loads, the two ELCIs are "seeing" that connection as a fault. However, I am getting this trip before I close any down stream breaker, so I don't see how that could be the issue. I have considered the possibility that the breakers are both bad, but the probability of both breakers being delivered faulty seems very low.

My next trouble shooting test will be to disconnect the load side lines for each ELCI breaker and see if this allows the breakers to close. I believe that this would simulate a "perfect condition" all breakers open situation. But before I start tearing everything else up, searching for some phantom ground, can anyone with experience see if I am doing something just terminally boneheaded?

I read one place where some suggested that the ELCIs should be upstream of the galvanic isolator, but since the ELCIs only monitor the neutral (white) and hot (black) lines and the galvanic isolator is monitoring the green line, it doesn't seem like this should be the case. Although, of course, the galvanic isolator monitor is hooked up to the white and the black lines for each shorepower connection. Perhaps those connections should be on the load side of the ELCIs instead of the line side?

Thanks for any help. If removing the load output from the ELCIs doesn't clear the problem, I will replace them with standard 30 amp breakers, but I really don't want to start swapping out equipment until I have ruled out everything else.

[pbiJim]

I'd start by using an ohm meter to look for potential shorts. Maybe the ground fault equipment is doing it's job correctly & you actually have a dangerous situation. I would try to rule that out first.

Another way to test for ground leakage is to put a clamp-on ammeter around the hot & neutral at the same time. It should read zero if the current is the same in the hot & neutral. If you read a current, it's probably leaking to an alternate return path somewhere. You might need to temporarily install the original breakers to do this test.

Ground faults trip when the current in the neutral is different from the current in the hot leg.Your 50amp to 2x30amp splitter may be causing your problem. some current from one hot leg may go back through the neutral on the other 30amp plug & cause a trip. Try totally disconnecting one of your 30 amp plugs & see if the other breaker still kicks out.

One of the codes has a little snippet in it about a boat only being fed from a single approved marine outlet. Your 50amp to 2x30amp splitter may violate that. I need to look it up before I can say that with any certainty, but it's probably worth checking on.

[goboatingnow]

The neutral lines for each ELCI run together to a single neutral buss, to which the neutral lines for all appliances are connected. This ties the neutral for the Cruisair HVAC unit to the neutrals for all of the other house loads.

I may have read this wrong, but its seems you have a common netural fed from two live sources each with its own ELCI. This will cause return currents to flow into teh wrong ELCI, causing each to trip

ANy common-ing of the neutrals needs to be behind the ELCI

dave

[CaptFrankM]

No, Dave, you didn't misread that. I do have the neutrals for both lines tied together downstream of the ELCIs. I suspect that you are correct and that they need to be separated. I was hoping someone would say that that wasn't the problem. I really didn't want to have to run a new line to create a second neutral buss.

I do like the idea of the splitter being part of the problem, but I am not sure that I see how that would affect downstream current flow. I have noticed that I get a slightly different voltage reading at the breakers themselves (about 1 volt). I attribute this to the different shore power cables (one is a year old, the other at least five) and slight differences in the internal wiring from the SP connections to the panel. I can check this by swapping the cables.

Oh, well, I will try the no-load test tonight and see if it makes a difference.

[CharlieJ]

With two 30A shore power supplies, the neutrals absolutely must be separated.

[CaptFrankM]

Thanks, Charlie. That's my next step.

I did the no-load test tonight and the breakers both closed with no problem. Then, I reconnected lines to the breakers and attached a single electrical socket to the wires. I plugged in a power tool and confirmed that it worked. Next, I checked that the ELCI trip function worked correctly.

So, the next step is to break the two neutral busses apart. Then, I will check the line with the single load to see if it works correctly. Assuming it does, I will start adding loads to the house line until either everything works or I figure out why not.

[smac999]

Originally Posted by CaptFrankM

In the old system, each shorepower line went to a dedicated 30 amp breaker, then to individual breakers. Because I added the generator, I added a Blue Sea three position selector switch (Shore-Off-Generator). From the selector switch, I now have two 30 amp ELCI breakers. These replaced the dedicated 30 amp breakers in each shorepower line, although they can now be fed by the two shorepower lines, or the generator..

once you get the N split up and fixed I would take another look at this.

did you just tie the 2 shore plug inputs together into the one switch?

really you need 2 of these switches. one for each line. unless it's like a quad pole switch.

I'm surprised your not blowing the dock breaker. because if this is the case, you are shorting the two 240v poles together of your 50a 240v plug at your switch. (or if you pluged into a dock with 2x30a plugs that were out of phase on the dock which would be pretty normal)

[goboatingnow]

You must separate the neutrals to get the ELCIs working. Everything that flows out of one Hot side of the particular ELCI must return to the ELCI on the associated neutral.

dave

[CaptFrankM]

Smac999,

No, I don't need two switches for the input and I am not running the two lines together. I am using a Blue Sea AC Rotary Switch (PN 9093), which takes the two lines in and keeps them separate.

Also, there is no 240 volt input. The marina that I am at just put in new power pedestals and they only have a 50 amp connector, rather than one or two 30 amp connectors. This is becoming more common, they tell me, for new installations, since so many boats are now running greater power requirements. From the 50 amp connector, I run a Marinco 50 amp to 2x30 amp splitter (PN 152AY). All the splitter does is break the power into two connections. It does no load splitting. Essentially, it works just like a household extension cord, where you have one plug but three sockets.

Since I am running two 30 amp load lines off of the cord, in theory, it would be possible to try to run 60 amps through the system. However, this would throw the breaker at the dock, so 50 amps becomes the limiting factor. Of course, if you had a boat set up that required more than 50 amps on a regular basis, you would probably want to go to a 100 amp system. I think with all my normal loads going, I would max out at about 35 amps, 25 on one line and 10 on the other.

Dave, I have come to accept that you are right. I suspected it all along, but I really didn't want to have to crawl into the engine room one more time to break that buss apart. I was REALLY hoping someone would tell me that wasn't the problem - SIGH.

It'll be a day or two before I can make this change, so I'll see what happens afterwards. Hopefully, this will clear everything up and I will be able to start troubleshooting the NEXT problem...whatever that will be.

[goboatingnow]

Originally Posted by CaptFrankM

Smac999,


Dave, I have come to accept that you are right. I suspected it all along, but I really didn't want to have to crawl into the engine room one more time to break that buss apart. I was REALLY hoping someone would tell me that wasn't the problem - SIGH.

Most people do in the end !!!!

Dave

[CaptFrankM]

By the way, if you chose to sneak aboard my boat and make the change yourself, just to prove you were right, it wouldn't upset me. I am busy this evening, so you could get in and out without me knowing. In fact, I could even leave the companionway unlocked if that would help!!

[goboatingnow]

Originally Posted by CaptFrankM

By the way, if you chose to sneak aboard my boat and make the change yourself, just to prove you were right, it wouldn't upset me. I am busy this evening, so you could get in and out without me knowing. In fact, I could even leave the companionway unlocked if that would help!!

a sort of "reverse" borrowers

dave

[CaptFrankM]

I prefer to think of it as the elves and the shoemaker! In fact, if you get the electrical work done, I can leave the rest of my" to-do" list out. Feel free to knock out any jobs you feel qualified for!

[bglad]

Reference below: 240 x 50 = 120 x 100. The equivalent generator to the 240/50 dock power would be 12 kw.

Since I am running two 30 amp load lines off of the cord, in theory, it would be possible to try to run 60 amps through the system. However, this would throw the breaker at the dock, so 50 amps becomes the limiting factor. Of course, if you had a boat set up that required more than 50 amps on a regular basis, you would probably want to go to a 100 amp system. I think with all my normal loads going, I would max out at about 35 amps, 25 on one line and 10 on the other.

[CaptFrankM]

Sorry, glad, you lost me. While I agree with your statement, I don't see what it has to do with my situation. I have no 240 volt lines anywhere in my system. Everything is 120 volt.