ABYC Standards

[High Hopes]

Thanks, Jerry

[High Hopes]

Hi Shawn,

I found your drawing. Might I make a few suggestions.

- You have two 100 amp fuses in a row. If the first one blows, your entire boat will be dead. These fuses need to be in parallel, one going to the engine (main bus), one going to the house panel.

- I once measured the starting current on my A-4. It hit 160 amps. A 100 amp breaker will trip. You can hard wire the starter motor without a fuse directly from the battery switch.

- What is a Power Line Isolator? Is it a switch? Can you provide a part number so I can look it up?

- What purpose does the Power Post serve? You want to have as few connections as possible between the battery switch and the starter.

- The output of the alternator should go directly to a fuse (imho). You may avoid using a fuse here by wiring the alternator directly to the starter if you use a #4 wire.

- You need more fuses. As it stands now, everything has access to 100 amps. Use a 25 amp fuse for the engine circuits. I wouldn't think that you need more than 40 amps or so for your house circuits, a 60 amp fuse should do nicely.

I hope this helps.

Cheers,

Steve

[joe_db]

Here is how my boat is wired if it helps.
As of yet I am not fusing the starter lead. The starter draws about 130 amps, so I would need at least a 200 amp slow-blow fuse. That would not protect against much but a dead short.

[sastanley]

Steve, thanks for your advice.

You're right..that 100 amp fuse on the distro panel would kill everything in the boat (except the motor) - I could probably eliminate that considering I have the 100 AMP breaker that is integrated into the 1-2-both switch (Blue Sea #8062, no longer made, but, got it cheap)

I agree I need a fuse in the charging circuit between the alt. & the isolator. I'll have to look up the Powerline Isolator specs again...made by Hehr International. It is an old unit, & is a diode based isolator that will handle up to 70 amps I think.

The power post is a Blue Sea 2016 - I purchased that with the intent of breaking up the circuits in the engine room..what it really did was allow me to add a ground bus easily, although I could have simply run a 14# from the engine block..The (+) ended up not doing what I wanted (so it is just a connection point) because I still have to isolate the ignition voltage via the key. If I ever add a dedicated start battery (long range plan), this would likely be where I'd add it into the system & the start battery would have its own switches to isolate it from the rest of the boat.

[High Hopes]

Hi Shawn.

Change the panel fuse to 50 amps or so. That way, if the panel shorts, the 50 amp breaker trips and the 100 amp breaker stays on for the motor.

BTW, can you get to the common terminal of the switch before the breaker, that is, to the unfused input of the breaker?

Steve

[sastanley]

No..it is kinda integrated I think...I'll snap a pic for you the next time I am at the boat. I am sure with some fabricating, I could separate them.
I am currently chasing a failing coil I think due to over voltage issues in another thread. More on that tomorrow.

[ndutton]

I wanted to offer this about your overcurrent protection:

Regarding your 100 amp fuse and breaker, except for the cranking circuit where they're not required, in practical terms they're useless except for a catastrophic electrical failure. I'm heavy on electrical consumption and with everything running I consume less than 30 amps. That's refrigeration, radar, autopilot, halogen cabin lighting, water pressure pump, foredeck halogen light, running lights, etc., all operating simultaneously. The windlass (not yet installed) has a separate breaker so it doesn't factor in.

[sastanley]

Hi Neil,

I was thinking about that (consumption) in the other thread, where we are discussing my shutdowns, due to the (we are pretty sure) coil. I tried to load my boat up with everything I had to see if it lowered coil voltage (not everything is wired yet, however) and I could barely nudge the needle on the distro panel ammeter..I maybe got to 5 amps with every cabin light, VHF transmitting on high power, bilge pump, & running lights (2 of 3 are LED) on & according to my notes, no discernible change to the coil voltage.

The biggest draw on the boat may be the halogen deck light, which is not wired yet.

[joe_db]

My biggest draw is the shop-vac. That runs about 50 amps
The next biggest are the radios. The SSB and 2 meter both run over 20 amps.
As I replace my lights bit by bit with LEDs, the normal lighting load is dropping to almost nothing.

[Administrator]

My biggest draw is the shop-vac. That runs about 50 amps
The next biggest are the radios. The SSB and 2 meter both run over 20 amps.

Geez! Are you sure?!

Bill

[TomG]

My biggest draw is the shop-vac. That runs about 50 amps
The next biggest are the radios. The SSB and 2 meter both run over 20 amps.
As I replace my lights bit by bit with LEDs, the normal lighting load is dropping to almost nothing.

I'll bet that's one bad-ass shop-vac!

[youtube]y4sOfO8Ei1g[/YOUTUBE]

[joe_db]

I am quite sure. I have to use it in small bursts or it either blows the inverter circuit breaker or the inverter does a thermal shutdown. Keep in mind a 5-amp draw at 120 volts = 50 amps at 12 volts. A bigger inverter and breaker are in the works.

Geez! Are you sure?!

Bill

[Mo]

Now you guys have my attention. I have a 1 Gallon Shop Vac on the boat also and I plug into a 1000W inverter. It will run for a couple of seconds then trip the inverter breaker.

If I start the engine it works fine. So, in short, I need the engine running to run the shop vac. I have two starter/deep cylce batteries aboard and I figured those would run that.

My next biggest draw is Radar. Raytheon 40XX....I used it just this morning when I got myself in the thick of it. The radar is just wired in and works fine with or without the engine running. I have to watch the power for sure with that going.

So, what's the deal with the inverter and shop vac. I put heavy wire from the inverter to batteries. Never though much of it until I saw Bills post.

Edit: I will run down to the boat here shortly and get the info off the Vac and batteries and wiring from the shop vac to batteries.

[ndutton]

Mama Mia, another spicy meatball!

Mo et. al.,

I looked up the specs of your vacuum. It's difficult to read in the picture but the electrical rating at 120VAC is 6.5 amps which equals 780 watts. Your inverter is rated at 1000 watts so we should be good, yes?

Maybe not.

For the inverter to put out 780 watts, even if it operated at 100% efficiency - which it doesn't - you would need a continuous 12VDC input current of 65 amps minimum. That means #4 wire from the battery to the inverter. Is that what you have? To realize the full 1000 watts - again assuming 100% efficiency - you need 83.3 amps @ 12VDC or #2 wire.

Smaller wires on the input side will result in a serious voltage drop and the longer they are the worse the drop and that, I suspect, is the root of your problem.

I can't possibly know the intricacies of your inverter installation but I suspect too small 12VDC input wires. Beef them up and I think your problem will disappear. Well, at least the overload tripping problem will. Battery consumption is another matter.

Ever consider a broom and dustpan? Dustbuster?

I don't know that the following observation includes you Shop Vac guys but it's interesting there's a general aversion to refrigeration because of power consumption but a vacuum that hammers the living Hell out of a battery is OK?

edit:
I did a little more research and the typical inverter efficiency claim is 90%. Real world usage is more like 75%. Using the 75% figure, the most you can expect (continuous) from a 1000 watt inverter is 750 watts and that's with the 83.3 amp @12VDC input (#2 wire - bigger than what we run to our starters). I've seen this sort of thing on phase converters. We really have to oversize them for reliable operation.

Factoring in the efficiency loss, when considering a 120VAC appliance powered through an inverter, take the 120V amperage and multiply it by 13.3 to find the 12VDC amperage required to run it.

[Administrator]

Joe:

It was the amps quoted for the radios that befuddled me.

Bill