DC diagram review

[flee27]

Can you please look over the attached DC wiring diagram and let me know if I am missing anything required to be correct. My new to me boat has all the equipment shown and everything works. It is was wired for function and not wired "correctly". Everything does appear to be actual marine wire, so that is good. I will be adding some of the cutoffs and fuses shown in the diagram. This not how it currently is wired. This is what I propose to change it to.

Thanks

[CharlieJ]

Looks good. You need a case ground on your inverter.

[Spot]

What are the small devices at this junction point?

[rgleason]

Originally Posted by Spot

What are the small devices at this junction point?

Fuses, see this discussion about types of fuses
https://www.cruisersforum.com/forums...us-243374.html

ANL Fuse, ANL Fuse Holder

ATC Fuse ATC/ATO Fuse Holder larger than ATM, can have an LED indicator

ATM Fuse for miniature version of ATO/ATC

MBRF Fuse and Holder, Dual MBRF Fuse and Holders


I believe these represent MBRF Fuses but the OP will hopefully advise.

[Sparx]

If the MRBF terminal fuses were swapped for Blue Seas 285 series breakers or equivalent then I don't think the isolation switches are required, saving some money. I prefer breakers over fuses in these capplucations because breakers can be reset. The breakers need to be located close to the bus.

https://www.amazon.com/dp/B0051OWRHE...ing=UTF8&psc=1

[CarlF]

Use this voltage drop calculator to check that the wire gauge is big enough.

Check especially bow thruster and anchor windlass since they are presumably a long way from the battery.

https://www.genuinedealz.com/pages/v...rop-calculator

Should you need some new heavy cables, I've been using Genuinedealz for years to make up custom cables. He'll use the end fittings and shrink tube of your choice. His crimps are works of art - far better than you'll get from most boatyards. He only charges about $5 per cable on top of the components.

[rgleason]

Originally Posted by Sparx

If the MRBF terminal fuses were swapped for Blue Seas 285 series breakers or equivalent then I don't think the isolation switches are required, saving some money. I prefer breakers over fuses in these capplucations because breakers can be reset. The breakers need to be located close to the bus.

https://www.amazon.com/dp/B0051OWRHE...ing=UTF8&psc=1

Are the Blue Seas 285 comparable to MRBF in terms of safety characteristics?

• Max Voltage: 48V DC, Interrupt Capacity: 3000A @ 48V
• Terminal Size: 1/4" Ring Terminal

PS here is an MRBF 285 version which provides both switch and circuit protection

• Rated IP66 Waterproof
• Max voltage: 48V DC, Interrupt capacity: 5000A @12V, 3000A @ 24V, 1500A @ 42V
• Terminal Size: 5/16"-18

Would these be okay in a covered cockpit locker that is gasketed?

[DougR]

Where do you connect the starter motor, and how do you power the starter from the opposite battery bank if necessary?

[calmissile]

I like those Klixon breakers. Can they be manually tripped (turned off)? If so I will install them on my boat.

[smac999]

Alternator and combiner need own fuse. Don’t share.

The mrbf on the house battery is Likly too small to power everything. Since they are max 300a

[MerMike]

Are you powering your DC distribution panel, bow thruster and windlass from the same cable? Have you done a load calculation to determine wire size needed? You might be better served with separate cables for each of those loads. The switch ahead of the switched buss doesn't seem to get you much.

I'm curious as to the logic behind charging the start battery with the alternator and using a combiner to charge the house bank. What size is your alternator? What type of battery and what and capacity is the house bank? It seems logical to charge the largest load with the alternator, unless it's so small you are concerned about overloading. Depending on the battery type, you may not be able to deliver a sufficient charge with this setup.

Do you have a shore power connection? If so, an ELCI and polarity indicator is required, as is a separate case ground from the inverter to the AC ground bus. A galvanic isolator is recommended.

[Sparx]

All of the 285 series thermal breakers i have encountered can be manually tripped, allowing the breaker to serve the function of an isolation switch too.

Note that surface mount and panel mount models are available. The panel mount models put the wires behind the panel, which is useful in potentially damp locations.

[goboatingnow]

Can someone explain to me the logic behind the ABYC requirement to ground inverter cases , I presume you all mean connect to mains earth , rather then dc 0V

All my inverters have the case isolated

The issue is if you want to retain RCD( ELCI ) protection , to do that if your inverter is driving your whole boat system , then you need a connection between the boats protective mains earth wire and neutral at the inverter.

Given the lack of fault paths , I’m not sure in boat RCD protection is a lot of use with inverters anyway and traditionally I bypass them on inverter activation

I see no point or advantage in connecting the case per se.

[rgleason]

Originally Posted by CarlF

Use this voltage drop calculator to check that the wire gauge is big enough.

Check especially bow thruster and anchor windlass since they are presumably a long way from the battery.

https://www.genuinedealz.com/pages/v...rop-calculator

It does not work.Try the Blue Seas calculator

https://www.bluesea.com/support/arti...r_a_DC_Circuit

https://www.southwire.com/calculator-vdrop


You might want a Service switch in the Engine compartment on the Alternator wire. I would probably connect the alternator to the house bank as that is the major bank and will have a longer bulk period.

[MerMike]

Originally Posted by goboatingnow

Can someone explain to me the logic behind the ABYC requirement to ground inverter cases , I presume you all mean connect to mains earth , rather then dc 0V.

The theory behind requiring a separate AC case ground is that it provides a more direct path to AC ground for a fault than via the DC case ground.

The AC ground, the DC ground and the DC case ground should be tied together at the DC ground bus, but the committee decided that that is not a sufficiently direct path and that a separate wire from the case to AC ground is needed.