Neutral and ground tied together at panel

[ybrad]

OK, get this.
After four+ years into my project (1980 37C), I've finally decided to tackle the 115 vAC system. Never mind that the boat came to me with an extension cord (18ga) plug wire-nutted onto the end of the main supply wires (since that had melted off the SP receptical). Of course, I never powered up this configuration!

Here's what I found yesterday while examining main feed into the AC panel:
Green- onto the grounding TS. (That's OK)
White- onto the DPDT master CB. Switched side goes to the neutral TS. (That's Ok)
Black-onto one of the SPDT CBs. Switched side of this CB is the bus bar that poweres the remaining SPDT CBs for other circuits. (Starting to get weird)
And finally, here's what is happening on the second pole of the DPDT master CB: it is fed by the neutral TS (ugh?); further more, the switched side of this CB is tied to the grounding TS (!!!).

To reiterate, I never put power on this system. What I discovered is way off the ABYC norm (as I understand it), and my first thought (biased by the afore mentioned 'extension cord plug') is a grossly incompetence rewire attempt.

Any other thoughts? Perhaps a misguided attempt to accomodate a 'suitcase generator'? My plan is to return the system to normal configuration.

QUESTION: I didn't find any circuit protection from the SP receptical end to the main AC panel. This is a long length of wire. Is protection recommended near the SP end? If yes, would a 30A DPDT CB suffice?

 

[Maine Sail]

*If the wire run between the shore power inlet and the main AC panel breaker is longer than 10 wire feet then a breaker should be installed at the inlet. It should be a double pole breaker interrupting both HOT and NEUTRAL and sized not to exceed your wire inlet size eg: 30A for 10GA wire....

*At the AC panel a 30A double pole breaker (could be 50A if your wiring is set up for it) to interrupt both HOT and NEUTRAL will also be needed. Any AC main breaker needs to break both HOT and NEUTRAL simultaneously.

*The GREEN/GROUNDING wire is never interrupted with a breaker and is tied to your on-board DC ground bus. AC NEUTRAL/WHITE & GROUNDING/GREEN are NEVER tied together on-board the vessel except at a new "source" of power such as an inverter, genset, or isolation transformer.

*You will also need a reverse polarity indicator in the AC system.

*If an inverter is fitted then there must be a means of transferring power so that the two sources can be completely isolated and never be "on" at the same time.

 

[ybrad]

Thanks for the input MS. Good gouge on the 10' between SP inlet and panel; with my SP relocated to the port side, it may be under 10'; TBD.
Good review of important points, too. I'll be returning the system to proper configuration as you (and ABYC) described. It will see some service from a Honda 2000ei as well as dock SP.

Out of curiosity, in your wide experience, have you encountered a boat as mis-wired as I what I encountered?

 

[Bill Roosa]

Important safety tip; if you have a water heater that has an electric heater in addition to the engine coolant then make sure the genset will have enough capacity to power it. Also the battery charger should not be able to be powered if the inverter is on. if you have appliances that can run on shore power but not the genset you need some method of keeping the brother-in-law from trying to take a how shower while at anchor...... you get the idea. Could be as simple as color coding the panel to indicate what is and is not permissible while using the genset or inverter. You can also set up the source selector switch and CB powering schema to do this auto magically.

 

[Sailvayu]

In addition ABYC recommends all 120 VAC outlets in wet locations be GFIC type. So any outlets in the head or Galley should be GFIC.

Also your AC ground needs to be tied to your DC ground buss. This is to give any fault a path to ground. You cannot assume the shore ground is indeed connected to ground you need that on the boat as well.

Capt. Wayne Canning, AMS
www.projectboatzen.com

 

[ybrad]

NEW FINDINGS....upon further dis-assembly of the existing AC panel, it turns out that the 115 vAC main CB is not two pole, but three pole. Don't recall seeing these before. Are they commonly used??

The installation makes a little more sense;the hot and neutral were properly on the breaker. However, the 3rd pole was the odd-job tying the neutral and ground buses together. As it turns out, that 3rd pole flunked the continuity test with a VOM anyway. So the buses weren't tied, at least at this juncture. (Not that I would have powered it anyway!)

A new DPST main is going to be installed. Also existing wiring to be evaluated for continued use or not and GFCI recepticals to be installed.

(Note: oops, in original post I typed DPDT and SPDT, but that wasn't correct;they are single throw.)

 

[onecoolair]

third pole maybe for second leg

NEW FINDINGS....upon further dis-assembly of the existing AC panel, it turns out that the 115 vAC main CB is not two pole, but three pole. Don't recall seeing these before. Are they commonly used??

The installation makes a little more sense;the hot and neutral were properly on the breaker. However, the 3rd pole was the odd-job tying the neutral and ground buses together. As it turns out, that 3rd pole flunked the continuity test with a VOM anyway. So the buses weren't tied, at least at this juncture. (Not that I would have powered it anyway!)

A new DPST main is going to be installed. Also existing wiring to be evaluated for continued use or not and GFCI recepticals to be installed.

(Note: oops, in original post I typed DPDT and SPDT, but that wasn't correct;they are single throw.)

Third pole ??? Hmmm?.... Second leg?
Maybe .......For separate A and B side on a 120vAC breaker panel.... Two legs would also allow for a 220vAC service.

 

[Sailvayu]

Do you have a photo of the back of the breaker. There are some that are 3 pole that will trip it you have a reverse polarity from the shore power. What you describe sounds a bit like this but I would have to see it to know for sure.

Capt. Wayne Canning, AMS
www.projectboatzen.com

 

[Paul F]

The 1980 37 is likely factory wired like my 1980 33. The three pole hook-up bothered me for a time. It is a polarity check and will stop current flow if the source is sending the wrong polarity. I move my boat around a lot and find about half (small marinas) have their wiring backward. I have even made up a jump cord to correct this when the marina would not rewire their circuits. You know how to wire around this check, however I have used it for many years. I also have a GFIC for all wiring.

 

[uncledom]

That third pole might be there so you can isolate the marina and the rest of the world from your DC buss when you're not using AC.