Where to connect a 500 watt inverter and what size wires ...

[Mike Dyslin]

Hi,

I want to install a small 500 watt pure sine wave inverter (photo 1 & 2) on my 355.  The inverter has positive, negative and ground terminals.

I would like to mount the inverter in the compartment under the shelf in front of the nav station which is pretty close to the electrical panel and batteries.  See the red circled area in photo 3.

Where is a safe and convenient place to attach the inverter positive, negative and ground wires?

What size should these wires be?

I did temporarily attach the positive and negative wires behind the electrical panel to the red circled bus and the black circled bus in photo 4, just to see if it would work.  It did work and the amp meter showed how many amps it was drawing.  The main reason for the inverter is to power Starlink and my laptop.  It was generally drawing under 10 amps,  but may have peaked a bit higher.  I suspect I will try other devices that may draw more once this is available, so would like to wire it safely.

Also, what is the difference between the three  busses circled in photo 5?  This is the factory wiring on my 2012 355 (#38) so hopefully it is similar to others.

Thanks,

Mike

[ken magida]

I have #46 so we are the same vintage. I had my dealer install a 400 watt unit which looks somewhat similar to yours. I also use it for my laptop and printer. It is mounted on the shelf above the radio cabinet on the outboard end. It is wired to a dedicated circuit breaker which is all I know about that. My only concern with putting it in the cabinet is heat buildup. 

Ken Magida 

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On Jun 30, 2025, at 14:14, Mike Dyslin <mike....@gmail.com> wrote:

Hi,

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[Mike Dyslin]

Ah, yes, that makes sense to put in a breaker for it.  I have available slots.  Any idea what amperage circuit breaker I should use?  500 watts at 12 volts ~= 40 amps?  A 30 amp breaker to start with?  Anyone know where I can order breakers for our panels?

Fair Winds

Mike

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[ken magida]

 500 watts at 12 volt is close to 40 amps

Defender has the breakers

They are blue sea brand

Ken Magida 

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On Jun 30, 2025, at 16:46, Mike Dyslin <mike....@gmail.com> wrote:



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[bill pittore]

Hi Mike,

 I would be concerned about heat as well in that small area. You could mount it under the nav desk which is where I put my Multiplus unit. Still plenty of room for your legs.

See inline for more responses.

On Jun 30, 2025, at 2:14 PM, Mike Dyslin <mike....@gmail.com> wrote:

Hi,

I want to install a small 500 watt pure sine wave inverter (photo 1 & 2) on my 355.  The inverter has positive, negative and ground terminals.

I would like to mount the inverter in the compartment under the shelf in front of the nav station which is pretty close to the electrical panel and batteries.  See the red circled area in photo 3.

Where is a safe and convenient place to attach the inverter positive, negative and ground wires?

Do you mean the DC input connections? You will need to install a 40 Amp breaker in a free slot. The positive cable would go from the load side of that new breaker to the + DC IN connector. The - DC IN from the inverter would connect to the DC negative busbar which is the one on the left with all the yellow wires attached to it. The ground from the inverter would go to the same busbar.

What size should these wires be?

12 AWG wire is rated for 45A but that’s cutting it close. I would use 10 AWG wire. The ground wire can be one wire size smaller so you could use 12 for that.

I did temporarily attach the positive and negative wires behind the electrical panel to the red circled bus and the black circled bus in photo 4, just to see if it would work.  It did work and the amp meter showed how many amps it was drawing.  The main reason for the inverter is to power Starlink and my laptop.  It was generally drawing under 10 amps,  but may have peaked a bit higher.  I suspect I will try other devices that may draw more once this is available, so would like to wire it safely.

Do not connect any DC stuff to that busbar on the right. That bus on the right is the ground and neutral of the AC side. Don’t connect your DC negative wires to that bus.

Also, what is the difference between the three  busses circled in photo 5?  This is the factory wiring on my 2012 355 (#38) so hopefully it is similar to others.

The bus on the left is the DC negative bus. On the right top that is the neutral wires from AC loads such as AC receptacles. The green wires on the bottom are ground wires from those same receptacles. 

Bill

[Mike Dyslin]

Thanks everyone!  This information is very helpful.

My plan now is to:

1. Mount the inverter under the nav station in the open air.  I suspect I will have to drill a hole somewhere to route the wires.
2. Buy a 40 amp circuit breaker.  Blue Sea Systems A-Series Toggle circuit breaker, 40 amp, single pole.
3. Positive 10 AWG red wire from the inverter + DC IN connector to the load side of the new 40 amp breaker.
4. Negative 10 AWG yellow wire from the inverter - DC IN connector to the DC negative busbar (mostly yellow wires on the left).
5. Ground 10 AWG yellow wire from the inverter ground connector also to the  DC negative busbar.
1. I don't see any open screws to use.  I also see several other wire pairs sharing the same connector, so I suspect it is valid for me to do the same.

Mike

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Fair Winds

Mike

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[bill pittore]

Hi Mke,

 This sounds good. I drilled into the fiberglass and fished my wires up to the rear of the breaker panel. It’s easier to fish if you remove the panel with the battery switches.

It’s ok with ABYC to have more than one wire on a connector. Don’t know the limit but it’s > 2. If you double up the larger wire generally goes on first with the smaller wire on top then the nut.

Bill

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