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Old 21-03-2019, 18:23   #1
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Individual power wiring or large wire and relays

I am installing a new ES120 plotter, with radar and a new evo 400 pilot with an octopus hydraulic ram. I will also be installing about 1000w of solar through an MPPT and possibly a wind generator. All of these things are at the back of the boat and the batteries are 30 ft forward.

If I run the plotter, radar and pilot straight from the 12 volt distribution panel than I will need to run about 25 ft of wire each way for each system. I will also need to run power wires for the solar panels back about 30 feet back to the battery box. Thats a lot of wires and it is not so much the cost of the wires as the space they need. I am running out of space. Who would have though you run out of space on a fairly large 50 foot boat.

What I am considering doing, is running a positive and negative 4/0 through the boat to act as a power bus. I would then take power off of this using relays to switch the chart plotter , radar and auto pilots from the main distribution panel. So control would be in the same place but actual power would come from the bus with lots of power available through the bus. I would keep extra relays on board in case they failed. Individual components would be fused as appropriate and I would put a 500 amp fuse on this 4/0 bus

I would then also hook up the output from the MPPT controllers to the 4/0 bus to send power back to the batteries from solar and possibly wind.

I am not an electrician or an electronics guru so I am here to ask some questions.

1) Is this set up safe?
2) Is this set up practical?
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Old 21-03-2019, 18:56   #2
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Re: Individual power wiring or large wire and relays

Yes, it can be safe and practical. But you have to consider how the circuit protection will be done. You will end up with circuit breakers or fuses at several non-standard locations. Thatís ok but may negate some benefits. A decent marine certified engineer or master electrician should advise you so you can stay compliant with fire and safety standards. The cost will not be insignificant but should be manageable.

Relays in the bowels of the boat controlled by switches at a control panel are somewhat common. But again, the circuit protection is where the details get tricky.

You may not want to feed the MPPT controller output into your long 4/0 bus cable. These controllers often generate a lot of electrical noise. It would be lowest risk of interference to feed the MPPT controller output directly to the batteries. You can afford a little more voltage drop on this pair of wires. But if you really get 1,000W you may wish to put the MPPT controller close to the batteries and run one or two pairs of solar wires to the controller. The solar panels will generally be higher voltage and lower current than the MPPT output. These panel fed wires should form a twisted pair if at all possible.

If it were me I would draw out a few (2-3) topologies and take them to a certified master electrician and have a talk about the pros and cons.
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Old 21-03-2019, 19:10   #3
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Re: Individual power wiring or large wire and relays

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Yes, it can be safe and practical. But you have to consider how the circuit protection will be done. You will end up with circuit breakers or fuses at several non-standard locations. Thatís ok but may negate some benefits. A decent marine certified engineer or master electrician should advise you so you can stay compliant with fire and safety standards. The cost will not be insignificant but should be manageable.

Relays in the bowels of the boat controlled by switches at a control panel are somewhat common. But again, the circuit protection is where the details get tricky.

You may not want to feed the MPPT controller output into your long 4/0 bus cable. These controllers often generate a lot of electrical noise. It would be lowest risk of interference to feed the MPPT controller output directly to the batteries. You can afford a little more voltage drop on this pair of wires. But if you really get 1,000W you may wish to put the MPPT controller close to the batteries and run one or two pairs of solar wires to the controller. The solar panels will generally be higher voltage and lower current than the MPPT output. These panel fed wires should form a twisted pair if at all possible.

If it were me I would draw out a few (2-3) topologies and take them to a certified master electrician and have a talk about the pros and cons.

The layout of the boat is such that I can put a mini distribution panel ( a box) at the back of the boat and fuse each pc of equipment as required and have the relays in there too. One stop shopping in the event of issues.



I don't know where you are but here in Toronto competent people in the boating industry are pretty hard to find. They may exist or they may not but if they exist at all they are very busy starting about now till Oct and then they go down south for the winter. This boat is heading down south in August so the chances of getting someone to help me at this point is slim to none.



Thanks for the information about the MPPT controller power being noisy. I will take that under consideration.
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Old 21-03-2019, 21:28   #4
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Re: Individual power wiring or large wire and relays

Running heavy cables from a central point to feed sub-panels at convenient places around the boat is a very reasonable way to do things, and can make the electrical system much easier to maintain and more logical. It sounds like you understand the basics of what you need to do for circuit protection.

With a bit of extra spend (maybe more than a bit...) you can use fancy relays (C-Zone being an example) that receive their signal right over the power wiring, or over a nmea2K network so you don't need to run a pair of control wires for each switched circuit.
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Old 21-03-2019, 22:44   #5
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Re: Individual power wiring or large wire and relays

The relays sound like way overkill. Why not just put them on breakers in the new aft panel and leave the breakers on? My chartplotter/radar and autopilot are on seperate breakers on my main panel, but they stay on except if we are storing the boat. They each have their own on/off switch at the units. In your case you can throw the main 4/0 cable breaker when you leave the boat and kill them all or climb back to the aft panel and throw the individual breakers

On the solar, if you run the solar to the controllers located near the batteries then you have less loss in tbe wires as the solar output is lower amps with higher volts before the controller.
I also think it is cleaner to separate consumers from charging sources.
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Old 22-03-2019, 08:34   #6
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Re: Individual power wiring or large wire and relays

I have both sub-panels and bus bars to distribute power from the house battery bank at the middle of the boat. I have the space and the existing gaps/holes in the structure to run longish runs, but for the SSB in the aft cabin, I am considering a separate battery that is charged from an ACR or a echo charger from the main bank; the SSB would run from this. The battery itself could be switchable to make it a (small) house bank should the main one go down. Proper fusing within proper distances, of course. And I tend to go bigger than needed for the wires where line losses may start coming into play.
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Old 22-03-2019, 08:44   #7
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Re: Individual power wiring or large wire and relays

You need to run 2 feeds. One switched and one Un switched.

The solar wind need to be unswitched to battery. And the nav off house switch.

Yiu could then just relay the single nav feed (all nav on / off). Or each one seperate if really wanted.
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Old 22-03-2019, 10:04   #8
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Re: Individual power wiring or large wire and relays

4/0 cable is way to much cable for what you are doing. You could run a hefty bow thruster on that size cable.

As already said, keep your solar charging wiring separate from you other wiring and run it directly to the batteries BUT in must be fused or have a circuit breaker near the batteries. Overload protection devices are there to protect the wiring. If the wire is shorted hundreds of amps could flow and fires could start.

Other than the hydraulic autopilot drive your loads are quite low. A sub panel at your nav station would be a good way to power them. I believe in KISS - keep it super simple. Relays and separate wiring to control them adds to the complexity of your system.

The hydraulic drive should be on it's own appropriately sized wire back to your main panel and should be on it's own circuit breaker.
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Old 22-03-2019, 12:13   #9
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Re: Individual power wiring or large wire and relays

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4/0 cable is way to much cable for what you are doing. You could run a hefty bow thruster on that size cable.
No electronics have ever died because they had to much current available to them through oversized cables. Fact is I am on a 50 foot boat. If I can't afford to oversize 60 ft of cabling I am in the wrong game. The difference between 3/0 and 4/0 is $1 a foot. Nothing.

As I said I am running out of room for cabling. My goal is to run as big a cable as I can into the back of the boat to get massive amounts of power available back there so I don't have to try and drag more cabling through the boat.


Everything will be appropriately breakered or fused individually.
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Old 22-03-2019, 13:13   #10
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Re: Individual power wiring or large wire and relays

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No electronics have ever died because they had to much current available to them through oversized cables. Fact is I am on a 50 foot boat. If I can't afford to oversize 60 ft of cabling I am in the wrong game. The difference between 3/0 and 4/0 is $1 a foot. Nothing.

As I said I am running out of room for cabling. My goal is to run as big a cable as I can into the back of the boat to get massive amounts of power available back there so I don't have to try and drag more cabling through the boat.


Everything will be appropriately breakered or fused individually.
For a 60 foot run a 40 amp load and 3% voltage drop you would need AWG 1 wire. For a 10% drop AWG 6. If you want to waste your money and deal with crimping the large terminals that is your business.

Even running one AWG 6 for your autopilot drive and a second one for your other electronics makes far more sense that 4/0 cable.

Even if you fuse or breaker each load individually you need to fuse or breaker that 4/0 cable at the battery. It is an ABYC requirement and therefore your insurance company requirement.
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Old 22-03-2019, 14:43   #11
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Re: Individual power wiring or large wire and relays

Have not read all the posts, but in case it has not been mentioned. You could run a heavy wire as your thinking and then just mount a sub panel, with breakers, near the instruments.



For the solar end you could just put a breaker in between the controller and the main line since you really never need to disconnect that except for maintenance or removal.


Not sure what the loads are but 4/0 sounds REALLY big. With today's electronics drawing much less I would think you could go much smaller. The chart I use shows regular #2 wire (not 2/0) is good for 50 amps at a 50 foot round trip distance.


Have to be a bit careful on a relay in the line between the controller and the main line. My controller (Morningstar MPPT) says do not have solar power going to the controller with the batteries disconnected.



Bill
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Old 22-03-2019, 17:31   #12
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Re: Individual power wiring or large wire and relays

i like your thinking and yes i would go with the large wire-- it is overkill but then you are DONE with it. i would go with the subpanel idea and not the relays- the relays add complexity without adding value. i am most of the way through redoing my boat electrical and i wish i had figured this idea out earlier instead of pulling all of the individual wires that i did- it would have been faster neater and easier. I do agree the solar panels should be on seperate wire- also you can buy relatively cheap clamp on chokes to go over power supply wires to SSB and other sensitive items that will take out electrical noise. good luck
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Old 22-03-2019, 18:02   #13
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Re: Individual power wiring or large wire and relays

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i like your thinking and yes i would go with the large wire-- it is overkill but then you are DONE with it. i would go with the subpanel idea and not the relays- the relays add complexity without adding value. i am most of the way through redoing my boat electrical and i wish i had figured this idea out earlier instead of pulling all of the individual wires that i did- it would have been faster neater and easier. I do agree the solar panels should be on seperate wire- also you can buy relatively cheap clamp on chokes to go over power supply wires to SSB and other sensitive items that will take out electrical noise. good luck

i like your thinking and yes i would go with the large wire-- it is overkill but then you are DONE with it.


My thoughts exactly. 2 big wires and I can run almost anything back there that I choose and never have to worry if there is enough juice. The batteries are over 30 ft from the aft end of the boat where the vast majority of power is consumed. The main panel is still 28 feet from the aft end of the boat. Lots of larger size wires running here and there and its become a mess IMHO. To look at it you might not think so but I am the one who has to deal with it so .....



I am well aware of how to calculate circuit loads. I can even calculate the total voltage drop if the gauge of the wire changes. ( thanks mr google )



I am still going to use the main distribution panel as the on off switching. It is physically large enough and high visibility to see what is off and on


I have enough extra breakers around that I can easily have them installed and ready to switch out the relays if they become a problem. In fact all of the high amperage breakers can be moved back to the back of the boat and act as the fuses until they have to work as switches in the event the relays don't work out.



All of this stuff will be installed in an easy access area in the aft part of the boat if it needs to be checked and or worked on.


As advised I will be putting the solar panels on separate wires. Of to see the solar panel guy next week.





Thanks to everyone
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Old 22-03-2019, 18:43   #14
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Re: Individual power wiring or large wire and relays

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Not sure what the loads are but 4/0 sounds REALLY big. With today's electronics drawing much less I would think you could go much smaller. The chart I use shows regular #2 wire (not 2/0) is good for 50 amps at a 50 foot round trip distance.

Bill
It is really big. That is the idea. 1 pair of wires running power to the back of the boat and then taking all power off there for all things in the back of the boat.

I am starting with the new plotter, new pilot and radar. I will add things as I move forward and will move other things that are currently connected through the main panel. All that stuff I just mentioned is just shy of 11K in beaver bucks. I don't want to burn out any of it due to current and voltage drop issues.

I have the tools including the crimper to do the job so its really not difficult.

I may also add electric motors to the jib winches and other things. By biting the bullet and making it really big now I don't have to redo it later. in fact if I had my thinking cap on right 5 years ago I would have saved a ton of headaches. Currently the wire chase looks like an old Bell Telephone switching station and for all intents and purposes it is full perhaps over full.

This site does the calculation on the wire size, load and voltage you specify. This link shows #2 wire, 50 amps 25 ft one way.

https://www.calculator.net/voltage-d...s=50&x=75&y=16


It shows voltage drop to be 3.26%. Does it make a difference. I don't know.

But by using 4/0 I can pull 100 amps out of the end of the wire 30 wire feet one way down to the back of the boat and still only have a 2.46 percent voltage drop. Now I have to add in the wire for the rest of the distance to the consumers. Those loads are much lighter but I will size them as if I have a 2.46 % voltage drop before adding the voltage drop for the remainder of the routing in the smaller wire.
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Old 23-03-2019, 01:27   #15
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Re: Individual power wiring or large wire and relays

Be sure to look at the solar charger specifications. Many models can be destroyed by disconnecting the battery while the solar panels are connected. Without the battery the internal electronics do not have power. Then the solar panel voltage rises because there is no place for the current to go (no battery) and this excess voltage damages the solar charger electronics. Many solar chargers require disconnecting the solar panels before disconnecting the battery.
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