AC green to DC negative buss ?

[hjohnson]

Originally Posted by s/v Jedi

No, there is no problem with seawater on deck or inside the boat. Even if there was, as the AC is not connected to it, there is no problem. You must envision that you always need to complete a circuit, through your body, before electrocution can take place.

The more stuff you connect AC power to, the more things can go wrong.

There’s no point in arguing this at this point. You’re free to believe what you want to believe, that’s fine. I’ll stick with a safer system that follows established practices and procedures.

There’s no point in continuing this argument.

[s/v Jedi]

Originally Posted by hjohnson

There’s no point in arguing this at this point. You’re free to believe what you want to believe, that’s fine. I’ll stick with a safer system that follows established practices and procedures.

There’s no point in continuing this argument.

You need to step back and look at the greater picture. Most of the world has established practices and procedures that match what I describe. Your window of reference is too small.

[team karst]

Originally Posted by hjohnson

…..



There is a very good reason as to why shoreside electrical codes are built this way.

Land based power distribution systems are designed to accommodate primary to secondary faults, and lightning paths to earth. Both could result in highly hazardous conditions with ungrounded systems and multiple users.
Our boats dont have high ac primary voltages, and few boats have any lightning countermeasures.
Overall, safety issues tend to concentrate on the individual boat with the problem.

Anyone hear of boat ac elevating the dc common mode system voltage?

[Hartleyg]

A bit OT, Jedi, but I noted a cable wrap similar to what you mentioned, but rated at 130 degrees C instead of 120 - the Amazon listing says it's made of "polyester" for whatever that means..
https://www.amazon.com/gp/product/B0...m_1p_1_lm?th=1


It's more expensive than the Alex Tech stuff that you & I like, and it comes in black only (no red or white).


Hartley
S/V Atsa

[s/v Jedi]

Originally Posted by Hartleyg

A bit OT, Jedi, but I noted a cable wrap similar to what you mentioned, but rated at 130 degrees C instead of 120 - the Amazon listing says it's made of "polyester" for whatever that means..
https://www.amazon.com/gp/product/B0...m_1p_1_lm?th=1

It's more expensive than the Alex Tech stuff that you & I like, and it comes in black only (no red or white).

Hartley
S/V Atsa

Thank you, put it on a wishlist for later use when needed

[jonathanv]

A good background on AC ground to common ground

https://www.youtube.com/watch?v=iUZwgI7e-vg

My 1999 European French production boat has a whole boat RCD with the AC ground and DC ground connected.

Another one with the ABYC diagram showing the AC grounding bus connected to the DC main negative bus bar:

https://www.youtube.com/watch?v=qi3FadG6mRc

[mcon12000]

The AC ground must be connected to the DC grounding bus.

PERIOD.

It’s one of the first things we check before starting an audit or work onboard a typical recreational boat with shore power.

If you don’t want to do it my employees won’t be working on your boat with anything powered on. We can all argue this until the cows come home but in court or arbitration after an avoidable accident you will loose if you decided you knew more than the panel of industry experts.

[s/v Jedi]

Yeah, DC ground… I’ve done away with it decennia ago

[Hartleyg]

MCON12000,


I'll ask the question: what is the "DC grounding buss"? The DC system does NOT use a ground for fault protection as the AC system does, so what are you calling the DC grounding buss?


Is it the lightning protection ground attached to the mast/rig/deck metal?
Is it the bonding system connecting the underwater metals?
Is it the ground plate used by the SSB radio?
Is it the engine/transmission?



Please explain!


Hartley
S/V Atsa

[jonathanv]

It's in the diagram:

[mcon12000]

For the sake of this discussion it’s the prop shaft which is accessed via the block. Could also be a plate below the waterline…

https://abycinc.org/blogpost/1839308...nded-or-Bonded

[svfinlandia]

Originally Posted by Fishspearit

The reason why ABYC says you should have the green AC grounding conductor connected to the DC negative bus is for safety. For example your battery charger shorts the ungrounded (hot, positive, whatever you want to call it) conductor to its housing. Then when you, a guest, or a worker is leaning their leg against your engine and touches the charger they get electrocuted as they are completing the circuit. This would not have happened if the AC grounding conductor were already connected to the DC negative bus as the ABYC recommends, and that is why they recommend it. The ONLY drawback to connecting the AC grounding conductor to the DC negative bus is that it can lead to galvanic corrosion because your grounding conductor is connected to other boats grounding conductors. But that's why you have a galvanic isolator. With the galvanic isolator in place and working there is NO drawback, and yet there is a BIG safety advantage to connecting the AC grounding conductor to the DC negative bus.

I see what you are saying, but is the green wire not connected to the case of the battery charger or whatever? And if the hot wire of the battery charger should short to the case it should immediately trip a breaker, either on the boat, or at the power post, whether or not the ground was connected to the DC ground. No?
Personally, I vote to keep the two grounds separate to avoid any possibility of getting AC into the water.

Al, S/V Finlandia

[svfinlandia]

Originally Posted by mcon12000

The AC ground must be connected to the DC grounding bus.

PERIOD.

It’s one of the first things we check before starting an audit or work onboard a typical recreational boat with shore power.

If you don’t want to do it my employees won’t be working on your boat with anything powered on. We can all argue this until the cows come home but in court or arbitration after an avoidable accident you will loose if you decided you knew more than the panel of industry experts.

Sounds like you lose a lot of jobs.

S/V Finlandia

[foufou]

Part of the AC and DC safety issues do start at the harbor wiring. Twice I have been called by a boat owner who was getting shocks while working on his propeller. Both times, at different boatyards, I tracked down the problem to a reverse polarity -hot and neutral- in the boat yard wiring. Scary!

[mcon12000]

Originally Posted by svfinlandia

Sounds like you lose a lot of jobs.

S/V Finlandia

It’s why I’m hired to do these things because they’re done correctly not someone’s best guess.

If you want to raise the risk of electrocution to anyone visiting your vessel that’s your choice. It’s not an option for us to disregard ABYC minimum standards when charging a customer for electrical work.

I assure you that if we took those questionable customers such as yourself we would later be blamed for the work you directed us to perform. Join ABYC and participate in the process so you don’t have to argue with me or anyone else about what you “Feel” is the correct way to approach this rather you can argue with the experts in each area these (minimum) standards overlap.

In the mean time call a local electrician and let them know you have a better way to wire your residence. I’m fairly certain you’ll receive a response similar to the ones you’ve already read here. Safety isn’t optional if you’re operating a business that deals with electricity.