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dougrose
#1 Posted : Tuesday, March 23, 2010 7:57:11 AM(UTC)
dougrose

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My AC panel was giving me fits - some of the breaker/switches were unreliable, and there was not enough slack in the wires from the boat to the breakers to let me pull the panel away from the console to work on the back. Several of the breakers were unreliable, and the bare copper connections between the Romex cable and the breakers had long ago turned green.

I needed a panel that could be removed for work, that allowed disconnecting one boat circuit at a time to check grounds, and that had reliable breakers.

I decided to use a standard household receptacle for each circuit, and hardwire the receptacles to the breakers in the panel. I would then install the whole magilla, and put plugs on each piece of romex so each circuit could plug into its receptacle. While I was doing plugs, I put in a 30 Amp box, wired back through the transformer to shore power, so that I could plug my panel into it, as follows:



Don't know if Marinette did this, but solid romex cable came up from below and wired directly to the breakers. Couldn't get the panel out, couldn't work on it, couldn't even reach in there with shore power on: note the hot bus bar.



Took out the panel and stripped it:



The new SnaPak breakers need a 1/2” hole:



Mounted the new breaker/switches, and the 30 A ammeter:



Rather than using an exposed hot bus, I wired each breaker to the power with insulated wire and connections:



I cut the back off of a 4-gang plastic electrical box, because there is no room for the whole box:



Wired up the receptacles, bussing the ground and neutral and leaving each hot long enough to reach its breaker:



Mounted the receptacles into the box. Note the 30 A plug, which will bring power to the panel:



Connected hot wires from the receptacles to the breakers and the shorepower hot to the meter. The receptacle box will fit easily through the panel cutout, so the receptacle box and panel assembly can be put in or taken out as one assembly. Feeding the box through:



Panel being installed:



The 30 A connector plugs into shore power (I added a box below the console), and the original romex cables to the boat get regular 3-prong plugs, so each can plug into the correct receptacle.

Finished panel: the upper meter is expanded ac volts, the lowest one is hertz. The meter on the panel itself reads 0 to 30 Amps ac. The voltmeter and frequency meter fill holes that were already in the panel.











1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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fastjeff
#2 Posted : Tuesday, March 23, 2010 9:22:16 AM(UTC)
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Wow!

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HuckFinn
#3 Posted : Tuesday, March 23, 2010 10:17:20 AM(UTC)
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Great tech article! Slick job. Thanks
PT-73
1973 32' FB Express
Chrysler 318's
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NightMoves
#4 Posted : Tuesday, March 23, 2010 10:26:30 AM(UTC)
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on my 70 express there is no panel there is a cuttler and hammer breaker box inside the space behind the lower helm sterring with access by a door over the stove,

Mike
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DiverDennis
#5 Posted : Tuesday, March 23, 2010 6:33:52 PM(UTC)
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Super nice job Doug. I have a couple of Qs:
*why not black (or some other color) for the line feed?
*is that #10AWG for the feed and 12 for the branch ckts?
*where is the gang box mounted?
*where did you get your breakers?
*what's the mosaic outlet for?
*is there a GFCI in the head?

Thanks for taking the time to post your project. Applause
DD
Surface Interval
1975 28' Express, Single M360
Specs: http://www.boatm8.com/my...amp;page=boats&arr=0
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dougrose
#6 Posted : Wednesday, March 24, 2010 12:37:42 AM(UTC)
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*why not black (or some other color) for the line feed?

It is common practice in aerospace to use white wire for everything, and put the color coding at the terminals. I mark the wire by wrapping colored tape around the terminal barrel and then putting clear heatshrink over it. I have a tape dispenser with all the colors. It looks normal to me. From a practical standpoint, I have one huge roll of #14 and another roll of #10 aviation wire that I bought from Skycraft in Orlando. It is good for this kind of thing: If I were wiring ac to the rest of the boat, I would use tricolor boat cable and get the color coding.

*is that #10AWG for the feed and 12 for the branch ckts?

Good eye. Actually, I am using 10 AWG for the feed and 14 AWG for the branch circuits. ABYC rates AWG14 at 29.8A in the engine room, 35A elsewhere. I am using "fast trip" breakers, which are "must trip" at 135% of nominal, or 27A, so the wire is protected within ABYC standards. ABYC rates AWG12 at 38.3A & 45A, but a fast breaker might allow over 50A. AWG10 is rated 51A & 60A, so is marginal in the engine room and OK elsewhere, for a 30A breaker. Marinette used AWG12 throughout. They would have been bounced from the Shuttle program in a heartbeat. Breakers: http://www.airpax.net/si...pax_PPP_SNAPAK_0106.pdf

*where is the gang box mounted?

The box goes below the panel, directly under the frequency meter, with the receptacles facing inward. The boat circuits are plugged into them. The 30A plug below the box plugs into a 30A receptacle (they are twist-locs) further down. For some reason, I forgot to get a pic of the plugs, sorry.

*where did you get your breakers?

http://www.pocosales.com/ I heard about these guys on this forum, and I recommend them without reservation.

*what's the mosaic outlet for?

MOSAIC is the on-board monitoring and alarm system. It will send a text message to my phone if AC power is lost (or a host of other things) and to do that it needs to "look" at the power. I mounted a receptacle near the unit to take a 110V to 9V wall wart, and that provides the signal to the MOSAIC. AC loss happens occasionally. I give it half an hour and if my boat hasn't been plugged in again, I call the marina. It's usually a tripped breaker for the whole dock, and I am usually the first to report it. Happens around 11 am, when everybody's air conditioning kicks in..... Once it reported a steadily running bilge pump. I got my buddy out of bed, he drove over at oh-dark-hundred, and found that the float switch had stuck on. One less buddy.....

*is there a GFCI in the head?

Actually, no. There should be, thanks for the reminder. I have a couple of those GFCI units that replace the receptacles, and I could put one in. Perhaps it would be best to protect the whole boat with a 30A gfci. I am currently protecting the personnel by "floating" the isolation transformer secondary and using a resistor between neutral and ground, not shown on this schematic. This is pretty old school and will not work with an inverter. Any opinions from the electricians out there?

I should mention that postings on this forum have saved me much grief, and I am grateful to all. I hope this helps someone.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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pfhlaw
#8 Posted : Wednesday, March 24, 2010 2:04:20 AM(UTC)
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Well done, sir.
Peter
1981 32' sedan bridge
twin Chrysler 360 cu. in. 250 hp engines
Raw water cooled
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DiverDennis
#7 Posted : Wednesday, March 24, 2010 6:53:16 PM(UTC)
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dougrose wrote:
*why not black (or some other color) for the line feed?

It is common practice in aerospace to use white wire for everything, and put the color coding at the terminals. I mark the wire by wrapping colored tape around the terminal barrel and then putting clear heatshrink over it. I have a tape dispenser with all the colors. It looks normal to me. From a practical standpoint, I have one huge roll of #14 and another roll of #10 aviation wire that I bought from Skycraft in Orlando. It is good for this kind of thing: If I were wiring ac to the rest of the boat, I would use tricolor boat cable and get the color coding.

*is that #10AWG for the feed and 12 for the branch ckts?

Good eye. Actually, I am using 10 AWG for the feed and 14 AWG for the branch circuits. ABYC rates AWG14 at 29.8A in the engine room, 35A elsewhere. I am using "fast trip" breakers, which are "must trip" at 135% of nominal, or 27A, so the wire is protected within ABYC standards. ABYC rates AWG12 at 38.3A & 45A, but a fast breaker might allow over 50A. AWG10 is rated 51A & 60A, so is marginal in the engine room and OK elsewhere, for a 30A breaker. Marinette used AWG12 throughout. They would have been bounced from the Shuttle program in a heartbeat. Breakers: http://www.airpax.net/si...pax_PPP_SNAPAK_0106.pdf

*where is the gang box mounted?

The box goes below the panel, directly under the frequency meter, with the receptacles facing inward. The boat circuits are plugged into them. The 30A plug below the box plugs into a 30A receptacle (they are twist-locs) further down. For some reason, I forgot to get a pic of the plugs, sorry.

*where did you get your breakers?

http://www.pocosales.com/ I heard about these guys on this forum, and I recommend them without reservation.

*what's the mosaic outlet for?

MOSAIC is the on-board monitoring and alarm system. It will send a text message to my phone if AC power is lost (or a host of other things) and to do that it needs to "look" at the power. I mounted a receptacle near the unit to take a 110V to 9V wall wart, and that provides the signal to the MOSAIC. AC loss happens occasionally. I give it half an hour and if my boat hasn't been plugged in again, I call the marina. It's usually a tripped breaker for the whole dock, and I am usually the first to report it. Happens around 11 am, when everybody's air conditioning kicks in..... Once it reported a steadily running bilge pump. I got my buddy out of bed, he drove over at oh-dark-hundred, and found that the float switch had stuck on. One less buddy.....

*is there a GFCI in the head?

Actually, no. There should be, thanks for the reminder. I have a couple of those GFCI units that replace the receptacles, and I could put one in. Perhaps it would be best to protect the whole boat with a 30A gfci. I am currently protecting the personnel by "floating" the isolation transformer secondary and using a resistor between neutral and ground, not shown on this schematic. This is pretty old school and will not work with an inverter. Any opinions from the electricians out there?

I should mention that postings on this forum have saved me much grief, and I am grateful to all. I hope this helps someone.
Excellent reply. Thank you.

Quote:
...I have one huge roll of #14 and another roll of #10 aviation wire...
MTW?

Quote:
Once it reported a steadily running bilge pump. I got my buddy out of bed, he drove over at oh-dark-hundred, and found that the float switch had stuck on. One less buddy.....
Funny stuff there :-)

Congrats on a fine job.
Surface Interval
1975 28' Express, Single M360
Specs: http://www.boatm8.com/my...amp;page=boats&arr=0
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dougrose
#9 Posted : Wednesday, March 24, 2010 11:36:34 PM(UTC)
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Sorry, I don't recognize "MTW", at least at 0730 I don't. Is it a question I could answer?

Thanks for the kind words.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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Roger2
#11 Posted : Thursday, March 25, 2010 2:59:37 AM(UTC)
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Doug,
I thought only coal mine electricans knew about resistance grounded systems.

Roger
Sea Jay
1983 37 double cabin, twin 230hp Volvo diesels, twin disk 1.5-1 20X 23 4 blade props
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dougrose
#12 Posted : Thursday, March 25, 2010 1:19:08 PM(UTC)
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Roger,

At one time Navy ships used a split system for DC: There was a +14V bus and a -14V bus, and loads (28V) were connected bus-to-bus. There was a resistor from the midpoint of the batteries to the hull, which kept the busses at +/- 14V, relative to the hull. When the + bus shorted to the hull, the bus became 0V and the other bus became -28V, and so on. The loads were not affected, and the short was easy to troubleshoot. Just keep unplugging stuff until the buss voltages bounce back to normal.

I like this system. It is particularly good for a metal boat, it makes it easy to keep the power off the hull. I was going to do it on my 32', but I could not get 28V coils for the starters, and new starters cost a grand each. So, I kept the conventional negative ground system. I put a shunt between the ground plate and the hull, so I can at least read the current that finds its way home through the aluminum.

The AC worked similarly. The generator winding (no generator, no ac) was connected right to hot and neutral. There was a resistor from neutral to hull. If the hot shorted to hull, then it became ground and the neutral would become hot. The short current was limited by the resistor, so it didn't kill folks or weld stuff. The short was easy to troubleshoot.

I am doing this at the moment, and I am OK with it. But, when I add an inverter it won't work because an inverter neutral is internally wired to ground. I will have to get some sort of gfi or something. I could put the gfi in the head outlet, or maybe something to protect all the circuits.

So, based on your experience, what would you recommend?


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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Roger2
#13 Posted : Thursday, March 25, 2010 2:00:29 PM(UTC)
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Doug,
You could ground (white & green) the inverter to top (netural) side of the grounding resistor. To be totaly propected you need a current relay in series with the resistor or a voltage relay across the resistor to provide a fault warning or trip.

Hope this is helpful.
Roger
Sea Jay
1983 37 double cabin, twin 230hp Volvo diesels, twin disk 1.5-1 20X 23 4 blade props
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DiverDennis
#10 Posted : Thursday, March 25, 2010 4:10:01 PM(UTC)
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dougrose wrote:
Sorry, I don't recognize "MTW", at least at 0730 I don't. Is it a question I could answer?Thanks for the kind words.
Sorry for confusing you. d'oh! MTW stands for 'machine tool wire' that is has a 'softer' feel than THHN.
Surface Interval
1975 28' Express, Single M360
Specs: http://www.boatm8.com/my...amp;page=boats&arr=0
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dougrose
#14 Posted : Thursday, March 25, 2010 11:35:29 PM(UTC)
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OK, I have it. MTW is basically the soft stuff that power cords use, and THHN is basically the hard stuff that you pull through conduit.

The wire I use is more like THHN, but tinned and stranded 7 X 19, with an inner plastic insulation and a tough outer cover. It is pretty stiff and holds its shape. I bought the rolls of MIL-spec at Skycraft, and I don't remember the spec # (it's stenciled on the rolls) but it is likely leftovers from the space program, or airplane production. It is very good for wiring on the bench, but would drive you nuts if you were trying to wire stuff in place.

I guess the point of this whole thread is to show that it is far easier to wire stuff up on the bench as an assembly, test it, and then install it. If stuff comes apart with connectors, it can always be removed for rework. I believe that, had I been working at Marinette, I could have saved enough hours of standing in the boat trying to wire stuff in an awkward place to pay for the plugs and receptacles.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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