Calling all you Electrician- Types

risctaker · Post by **risctaker** » Fri Feb 03, 2012 1:21 pm

Hey!. Need some input on my current electric project to keep everything safe and cozy. I live aboard during the Winter to commute to NYC and was using standard 120vac heaters to stay warm. Thank God this has been a mild winter so far and these heaters haven't had to put out much (reminds me of an old girl friend). Anyway.... I am in the process of installing a competely separate 240 VAC system that will utilize the marina's 250v/50 amp service on the dock. So...I have already purchased and installed the following stuff:

50 amp shore power inlet
6awg 4-wire primary feed to the breaker box
New 240 VAC primary breaker box with the 50 amp double-pole breaker pre-installed
40 Amp load breaker to feed the 4 x 8.1 amp 2000 watt heaters
50 amp Galvanic isolator
12 awg wire to feed the individual heaters
etc etc.

Here's the 64K question!

The boat's existing factory twin 30 amp 120vac system is properly grounded and bonded. Can I simply run the ground wire from the 250 VAC system up to the existing ground bus bar in the 120vac breaker box and call it a day? Is it OK to interconnect the grounds from these two different voltage / amperage systems??? MY feeling is "yes" but I wanted to check with the collective experts on thsi forum!

Thanks
Steve (Risctaker)

Big D · Post by **Big D** » Fri Feb 03, 2012 5:59 pm

risctaker wrote:......Can I simply run the ground wire from the 250 VAC system up to the existing ground bus bar in the 120vac breaker box....

Yes you can Steve. While you're at it, check the condition of the existing ground wire to the grounding/earth point and ensure there is no resistance (2 ohms max) between earth block point and the vessel's ground block. You may want to review the size of this wire as well.

Sounds like you have 120/240 line coming in. Is that what the marina is supplying or is it only 240 which would be only 3 wire cable?

risctaker · Post by **risctaker** » Mon Feb 06, 2012 11:37 am

Hi "Big D". The Marina is supplying the 4-wire 125/250vac power so all my equipment is matched to this service. I will definitely check the resistance of the grounding as you suggested but I am not clear on your terminology. What or where exactly is the "..between earth block point and the vessel's ground block" ? Is the vessel's ground block the same as the ground bus bar in the 120 vac breaker box where all the green ground wires are run to? Where do I find the "earth block point". Thanks for the info and clarification.

Steve

rbcool · Post by **rbcool** » Mon Feb 06, 2012 1:01 pm

Steve, this is just MHO
There is only 2 things on this planet I'm afraid of..... Bees and Electricution. I have to recommend you pay an accredited Marine Electrician at least a consult fee if your not 105% sure of what your doing. I read an article not long ago about how a large % of boat fires are due to incorrect wiring.
Just a thought buddy

Ron

risctaker · Post by **risctaker** » Mon Feb 06, 2012 1:35 pm

You're advice is well taken. The only other thing I would add to your list of "bees" and "Electrocution" is "Pissed off Women"

aaronbocknek · Post by **aaronbocknek** » Mon Feb 06, 2012 8:01 pm

risctaker wrote:You're advice is well taken. The only other thing I would add to your list of "bees" and "Electrocution" is "Pissed off Women"

i'm afraid of clowns. no, seriously, i have a true phobia of clowns. they scare the crap out of me.
aaron

Big D · Post by **Big D** » Mon Feb 06, 2012 10:48 pm

The grounding block is what you would typically find in the electrical distribution panel where you would connect your circuit grounds. Though this ground would then be hard wired through the shore power cord back to the ground on the marina side, it should also be grounded to earth through the boat which would be the water. In such a case, there would be a ground wire from the distribution panel ground block to the vessel ground (earth). That is the wire I`m reffering to. Most manufacturers will ground to the engine block but it is best to ground through the hull to an exterior grounding plate.

Ron is correct in suggesting a consultation with a certified marine electrician. There may be local by-laws that dictate AC wiring methods. This topic is very complicated and generally fraught with misconceptions that can turn out to be down right dangerous. Even the pros get confused at times as there are several schools of thought if you will. It's not as easy as simply intruducing a new system without knowing how the vessel is currently wired. Doing so can introduce a dangerous situation, and change potentials that may contribute to rapid corrosion. Having said that, there are those that insist on grounding AC a certain way in order to avoid corrosion. Don`t let anyone tell you to ground AC in such a way to eliminate corrosion. The absolute only consideration that should be given to AC grounding is that of safety, period.

Steve, check and see if your neutral wire (white) in the distribution panel is connected to the ground block or the panel case in any way and let us know. Also, do you have a bonding system on board; are all your metal through hulls connected-wired together?

risctaker · Post by **risctaker** » Tue Feb 07, 2012 9:17 am

Hey Aaron...never tell anyone what your fears are. There are people out there that will take advantage of that information. That being said..what's your home address. I have this little motorized evil midget clown puppet with a 6 " hunting knife to send you for your night stand.

risctaker · Post by **risctaker** » Tue Feb 07, 2012 9:24 am

"Big D". Thanks. My boat has a very good bonding system that ties together everything metal below the water line. That includes thru-hulls, engines, trannys' V-Drives, Fuel Tanks, etc. Nice heavy bonding cables as well. Looks like 8AWG to me. I will pull the panel cover tonight and see if there is a separate grounding bus bar for the white (Neutral) and the Green (Ground). I know the new 50 amp case has only one bus bar with two connectors, so I'm assuming that it was designed to tie both the neutral and ground to the same bus bar. However, there is also a ground connection inside the case itself, so the neutral and ground can be separated. Looks like the case was designed to accomodate both topologies. Will post what I find tomorrow morning.

aaronbocknek · Post by **aaronbocknek** » Tue Feb 07, 2012 9:47 am

risctaker wrote:Hey Aaron...never tell anyone what your fears are. There are people out there that will take advantage of that information. That being said..what's your home address. I have this little motorized evil midget clown puppet with a 6 " hunting knife to send you for your night stand.

just sent you a PM.

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Calling all you Electrician- Types

Calling all you Electrician- Types

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