Hatt dual shoepower service wiring and VTA903 Cummins part

[REBrueckner]

Hatt dual shorepower service wiring and VTA903 Cummins part

I'm aboard a 1961 61ft Burger with dual 50 amp shorepower service and twin transformers. She has twin 1976 VTA903 450 HP Cummins. We are in the Chesapeake Bay, Solomons Island, Md, Washburns Marina, for 3 mos of refit. The new owner has been the owner of my former 1972 48 Hatt YF for the past 7 years. This will be a great boat again before long.

[1] Can anyone explain how Hatts with dual 50 amp 120/240 volt shorepower handle dual neutral wiring. We are trying to figure out whether the current arrangement on the Burger is satisfactory, even if not ideal, or not. One possible way to avoid connecting dual neutrals, which seems to be the ideal, is to have one service all 240 volt, no neutral...so there is no connection issue. If anyone can email a wiring diagram of a dual shorepower service with dual transformers, that would be fantastic: wbyeric@Chesapeake.net. [The current arrangement has the neutrals connected and we are getting slightly different recommendations.]

[2] We would like to find a replacement intercooler [aftercooler] as one of our four has been found to have a leak. Cummins Part # 217023. A recommended source would be VERY much appreciated.

[That's the source of the high sodium[salt] found in the oil analysis saga I posted about a few mos ago here. I will still post the final conclusion to the purchase saga before long, but meantime I am having too much fun back aboard a boat again. It's possible the aftercooler can be repaired, but even so we'll buy a new or used one to have as a spare in any case.

That's so very much.

 

[drburke]

Rob, just to be clear you are speaking of the input to the transformers, correct? Are you attempting to also use the 120V input, or just two 240Vs?

On my boat, I found the neutral for the 240V input had been cut, but when I examined the transformer manual I realized that is is unused for that plug. It is used for the 120V input as on page 12 of this manual:
http://www.charlesindustries.com/marine_manual/12i kva.pdf

Speaking off-the-cuff, it should be possible to parallel the transformers in any configuration if the 120V section is the same phase on both (H1, H2, H3 are wired same to boat connector). Recall this is the meaning of the phase "dot" on schematics.

A more serious concern is how the pedestal power is derived, but that can be checked with a voltmeter to confirm no AC between same conductors at the shore power cable ends (like pins on one to like pins on another).

Others may have a different opinion.

DAN

 

[SKYCHENEY]

On mine, one transformer is able to feed any number of sub-panels (ships services). So, Tranformer 1 could be switched to feed Ships Services 1 & 3, while Transformer 2 feeds Ships Service 2 or any other combination.

The key is to have breakers that switch both hots and the neutral together (3 pole). This way, both neutral lines are isolated from each other.

 

[REBrueckner]

The issue we are seeking clarification about is whether dual neutrals ABOARD a boat may be properly connected.....usually at a single point and then connected to a common ground....so this is not a shoreside powercable issue.

The ABYC expert says "no", Burger and Bruce Morrision think "yes" the neutrals may be connected and then gounded at a common point aboard. Washburn's owner Eric is familiar with Selene trawler wiring and they avoid the problem by having all 240 volt appliances and equipment on one circuit without running a neutral; the other 120/240v circuit is therefore wired in the usual manner. Bruce was kind enough to refer us to a Hatteras factory expert and if we get any further inputs I'll post them here.

Right now we have no clear explanation about WHY dual neutrals should not be connected. It might be because out of phase 50 AMP supplies from shore MIGHT cause an issue aboard......Some issues may be resolved via appropriately wired selection switches....Other issues MIGHT possibly arise because of the polarization transformers {not isolation transformers} aboard our Burger. I'm guessing whatever practice is employed could well result from some unusual circumstance that occurred and which we haven't thought of yet. Anyway, if we get a clear answer from Hatteras and maybe even a wiring diagram, I'm going to advocate THAT be what we do here.

Stay tuned.

 

[Boatsb]

If the system is working with no issues I'd leave it. Your working on a giant conductor to begin with. If Berger designed it and feels it should be a certain way why do you question their knowledge and expertise?

 

[jim rosenthal]

Burger have all the original wiring diagrams and layouts, right? They have always built metal boats and they are familiar with the issues involved in safely bringing AC from shore onto metal boats. I would think they should be the final authority on this. They are still in business, aren't they, so I think they would be the best source. If the wiring has been changed around since the boat was built, perhaps the best thing is to restore it to what it had when new.

 

[REBrueckner]

We should have asked the owner to get the Burger schematic....good suggestion...
I did not discuss with Burger myself so don't know exactly what transpired....What we do know is that the Burger advice and ABYC 'expert' advice conflict.

BUT things change over the years...what was done in 1961 may no longer be what is ABYC approved today. For example, I had a 1961 Matthews with a single transformer with TWO WIRE on board floating 120v circuitry. That proved to have some deficiencies and has been superspeded for many years.

What we are 95% sure about is that over the years the original Burger wiring has been changed/supplemented/augmented...call it what you will....

Another complicating factor is that the wiring we see onboard has only 240 volt devices on one of the two circuits....like the Selene arrangement...yet there IS a neutral there!! Should that be removed?? And we would like to set up some electric heaters to operate from that circuit since it is almost unused in cool weather....to better balance the winter electric loads. And it just dawned on us we can bypass the issue of deriving a 120volt using that 'suspect' neutral by using some 240volt electric heaters.

 

[SKYCHENEY]

On my 1985, both transformers have their neutrals connected to ground at the transformer. Why would this be a problem? Power seeks its source. If there is a short to ground, it will find its way back to the transformer from where it originated.

 

[REBrueckner]

"On my 1985, both transformers have their neutrals connected to ground at the transformer.

That alone is very helpful to know.

" Why would this be a problem?.."

So far nobody can explain why it MIGHT be a 'problem'!! we are not sure it is an issue....yet the ABYC electrical expert Washburn's contacted says " not recommended".....

SKy, can you confirm that each of the transformers actually serves 120 volt loads? Or is one dedicated to 240 volt loads exclusively?

If the former, then apparently Hatteras considers tying the neutrals together [at the common ground point] is ok; if the latter, then they avoid the issue in the manner of the Selene Trawlers. [That's because in a 240 volt application the neutral is not even used.]

 

[REBrueckner]

Got a reply from the current Hatteras Service manager: Hatteras DOES connect separate neutrals from two separate isolation transformers together at a common neutral buss.

To recap, ABYC says 'not recommended', presumably for reasons analogous to it not being a good idea to use two 30amp connectors in a "Y" configuration to create a single 50 amp shorepower service at shorepower dockside pedestal.

Regardless, we are able to conveniently utilize the "Selene" approach which is to have one of the transformers dedicated to 240 voltage exclusively, not utilizing a neutral and hence avoiding the issue. So we have only one neutral whichof course connects to ground at a single point in the usual manner.

This is an aluminum hull with excellent hull condition, still within new specs after 54 years as I recall, and it has other wiring issues we cannot risk compromising further. Problem solved.

 

[SKYCHENEY]

"On my 1985, both transformers have their neutrals connected to ground at the transformer.

That alone is very helpful to know.

" Why would this be a problem?.."

So far nobody can explain why it MIGHT be a 'problem'!! we are not sure it is an issue....yet the ABYC electrical expert Washburn's contacted says " not recommended".....

SKy, can you confirm that each of the transformers actually serves 120 volt loads? Or is one dedicated to 240 volt loads exclusively?

If the former, then apparently Hatteras considers tying the neutrals together [at the common ground point] is ok; if the latter, then they avoid the issue in the manner of the Selene Trawlers. [That's because in a 240 volt application the neutral is not even used.]

Yes, both transformers serve 120v loads. I just explained how either transformer can be switched to power any or all "ships service" sub-panels. Each sub-panel has a combination of 240v and 120v loads.