Alpha One Gen II Question---- Electrical problem

[Grandad]

Re: Alpha One Gen II Question---- Electrical problem

I know my limitations and electricity to me is a science that I leave to the professional's. Where would the ground be connected for the ac on my boat. I found the green ground cable from the main ac panel and I understand it is connected to the hull. Is there a ground pad molded in the hull somewhere. I would gather that it would be in the engine compartment somewhere. Am I correct to think so? Thanks for all the help.

Your boat's electrical system connection to ground should connect (bond is the correct term) your battery's negative DC, your engines, and all exposed metal on miscellaneous 120V appliances together. This bonding system on your boat should not connect directly to the ground wire in the shore power cable. These 2 systems have the same purpose, but their interconnection should be via a ground isolation device.

This device can be a "ground isolator" which keeps the 2 systems normally isolated so that small voltage transients don't cause corrosion of metal parts that sit in the water. Under heavier fault conditions such as what it seems you're experiencing, the isolator recognizes the higher than normal voltage difference between the 2 ground systems and connects them together in anticipation that a fuse or breaker will now trip under overcurrent conditions.

A alternate (more expensive, but better) device is an isolation transformer often mounted on the boat that permanently isolates the shore power from the boat's 120V system. Properly wired, any 120V AC faults (shorts to ground) on the boat will be safely dealt with by your boat's fuses or breakers, with no current wanting to go ashore. There is no connection between the boat's metal parts and the shore power. So, I hope your electrician is aware of these two possible marine system types and doesn't bypass them in an attempt to apply standard land based rules that would join these two ground systems together. - Grandad

 

[Grandad]

Re: Alpha One Gen II Question---- Electrical problem

No! The Green Ground wire from the shore power is connected to all the metal parts on the boat whether they touch the water or not. I makes no difference.

Uncle Willie, this doesn't sound right to me. Are you familiar with ground isolators? - Grandad

 

[glenn property of pam]

Re: Alpha One Gen II Question---- Electrical problem

its a long read but this will ans most of the questions even if you do not fully understand how it works

Galvanic Isolators and Isolation Transformers

 

[glenn property of pam]

Re: Alpha One Gen II Question---- Electrical problem

So where does the green wire from the ac panel go?

the green from your panel goes to every metal item on the boat either by the wire or via the battery negative circuit. The green from shore to the boat is via a isolator that closes at a max of 1.4v (some models can close on sensing any level of ac on the boat side green wire). Your problem sounds like you have 30 plus volts on the ground so the isolator should be closed and the greens are joined but for some reason your boat can not drain the voltage on the ground and it sounds like the adapter as it also happens on a generator where you use the adapter (generator is internally connecting the neutral and ground or monitoring it). On the marina shore power you do not have a problem as the adapter is not used and any fault current is being grounded. Now heres where it gets intresting......is the ground wire at the marina carrying a fault to ground via the emergency green wire connected to shore or is this induced voltage. If its fault current then the gfci is meant to kick in and disconnect the boat alerting you that theres a small fault (large fault will trip the breaker).

 

[Firemedic724]

Re: Alpha One Gen II Question---- Electrical problem

Are you talking about the galvanic isolator? How can I test the isolator to see if it is bad?

 

[glenn property of pam]

Re: Alpha One Gen II Question---- Electrical problem

you can test the isolator but thats not going to be your problem as there should never be any voltage on the ground in the first place. If you have a digital meter you could proberly stick one prob in the grass and touch the other to the boat and see voltage (if you can sense it then a dvm will read it). do the ohm test on the adapter and fill in the numbers on post #34.

 

[UncleWillie]

Re: Alpha One Gen II Question---- Electrical problem

Uncle Willie, this doesn't sound right to me. Are you familiar with ground isolators? - Grandad

I haven't owned a boat with shore power.
But ultimately, the Shore Ground is connected to the boats DC ground system,
either through a Ground Isolator (Preferred for Galvanic Reduction) or directly connected (Not Unheard of).

Leaving the two ground systems NOT connected together by some means would be a mistake.

 

[Grandad]

Re: Alpha One Gen II Question---- Electrical problem

Leaving the two ground systems NOT connected together by some means would be a mistake.

UncleWille, If you use an isolation transformer, the benefit is lost if you join the 2 systems together. There would be no benefit to using the transformer. The OP probably doesn't have an isolation transformer anyway, but others may benefit from this thread. See what the ABYC Standard has to say in this PDF. - Grandad

 

[UncleWillie]

Re: Alpha One Gen II Question---- Electrical problem

UncleWille, If you use an isolation transformer, the benefit is lost if you join the 2 systems together. There would be no benefit to using the transformer. The OP probably doesn't have an isolation transformer anyway, but others may benefit from this thread. See what the ABYC Standard has to say in this PDF. - Grandad

Grandad;

I agree! :joyous:
I understand the nuances of the various systems and also understand that others reading this may not.
The original situation under discussion did not mention any Isolation Transformers and and an assumption was made that none were present.

So I will exercise the right to edit and restate my previous statement to cover all bases. (I Hope!)

Ultimately, the Shore Power Ground is connected to the Marine DC Ground/Bonding system, (With Exception!)
either through a Ground Isolator (Preferred; For Galvanic Reduction) or directly connected (Not Unheard of).
Leaving the two ground systems NOT connected together by some means would be a mistake.

Exception:
If the Marine AC Power Installation utilizes an Isolation Transformer, then the Shore Power Ground and the Marine Grounds/Bonds need to remain completely separated.
All conductive, Non-Current Carring Objects aboard the boat are still obligated to be connected/Bonded together and the AC and DC ground systems aboard the boat are to remain connected together just as if the Isolation transformed were not present.
Leaving the two on board ground systems NOT connected together would be a mistake.

How does that sound?

 

[Firemedic724]

Re: Alpha One Gen II Question---- Electrical problem

Update! I pulled the panel out and had an electrician check it. Turned out to be a bad diode that prevented the ground from doing its job. A 6.00 part. I want to thank all of you for your help. Happy Boating to you all.

 

[Grandad]

Re: Alpha One Gen II Question---- Electrical problem

Grandad; How does that sound?

That sounds just ducky, UncleWillie. :becky: - Grandad

 

[UncleWillie]

Re: Alpha One Gen II Question---- Electrical problem

Update! I pulled the panel out and had an electrician check it. Turned out to be a bad diode that prevented the ground from doing its job. A 6.00 part. I want to thank all of you for your help. Happy Boating to you all.

Glad to hear you have a solution.

I interpret that to mean the Galvanic Isolator in the Ground circuit was the culprit.
Essentially an Open Ground in the Boat.

 

[Firemedic724]

Re: Alpha One Gen II Question---- Electrical problem

Yup an open ground. So I am picking up a new stud diode tomorrow in fact I decided to buy 3 or 4 to have on the boat. The electrician said a diode could burn out with a spike in voltage so I am playing it safe. I have learned a lot about electricity by dealing with this problem. I learned that I chose the right profession as a firefighter and not an electrician.

 

[glenn property of pam]

Re: Alpha One Gen II Question---- Electrical problem

i find that intresting that the generator tied in to the isolated side of the ground system as its normally tied into the un-isolated side but that might be because most generators are built in and not just plugged in. Due to this my quote on the isolator being the problem was incorrect. now im wondering how the dock hook up could have been any better than the home hook up. Anyway glad you have it fixed.

 

[Grandad]

Re: Alpha One Gen II Question---- Electrical problem

Yup an open ground. So I am picking up a new stud diode tomorrow in fact I decided to buy 3 or 4 to have on the boat. The electrician said a diode could burn out with a spike in voltage so I am playing it safe. I have learned a lot about electricity by dealing with this problem. I learned that I chose the right profession as a firefighter and not an electrician.

Firemedic, glad to hear the hazard has been fixed, but I'm still puzzled. Bonding everything to ground through a diode or not is just a safety valve for insuring that a breaker trips and bonded metal parts can't become alive when there is a short circuit.
So was there anything else discovered to explain where the errant electric current (and your shock) originated? Current flowing to ground at less than the 6 mA max that a GFCI will allow is still not a good thing. - Grandad