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Chas231

Wiring

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Moving into the wiring stage of the construction. Batteries are mounted, charger mounted, and power run to the helm. I'm thinking of using a prewired DC panel with switches and circuit breakers. Blue Sea Systems has a 13-position panel. Any issues with using this kind of panel, as opposed to a separate fuse or breaker block and switches?

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A Blue Sea panel would be fine for a Bluejacket.  13 positions may be a little overkill for the main panel.  I prefer to have some of the commonly used switches on the instrument panel where they are handy to the helm.  I used a small fuse block to distribute power to them.  You could use switches on the instrument panel fed from breaker/switches on the main panel but I find a problem with that.  The issue is that there are now two switches in the same power line and that can lead to confusion.  If you do use the breakers on the main panel for instrument panel switches, I think I would short out the main switch and just use the one on the instrument panel to operate whatever is wanted.

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. I'm thinking of using a prewired DC panel with switches and circuit breakers. Blue Sea Systems has a 13-position panel. Any issues with using this kind of panel, as opposed to a separate fuse or breaker block and switches?

I like Blue Seas components.  And if you have extra breakers,  just label them "Torpedo" or "Laser" or maybe "Ejector Seat".

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Your post wasn't a thread killer; this just seems to be a long project for me. I appreciate your help. Ended up with Paneltronics panels for the AC and DC systems. Still working on the wiring. When the motor was installed I asked the installer to run power to the helm. I understand I need a fuse on this line, close to the battery. Could I use a battery terminal fuse to meet this requirement? How do I determine the the amp rating for the fuse?

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I don't know what your power requirements are at the helm.  The total amount of power (Amps) needed determine the wire size and that in turn determines the fuse size.  Also the length of the wire dictates wire sizes. 

Here is a table with wire sizes and their maximum current allowed:  https://www.bluesea.com/resources/1437

 

For real high current like feeding a distribution panel I am using the Blue Sea  marine rated battery fuses.  They mount directly on the battery terminals.

Here is a link: https://www.bluesea.com/products/category/16/72/Fuse_Blocks/Terminal_Fuse_Blocks

 

I'm also in the process of wiring everything,  At least I like it better than doing plumbing.  I will try to get some pictures up on my Flickr page.

 

Egbert

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The ABYC guidelines call for the fuse to be within 10" of the battery and sufficient to protect the wire when carrying its full rated load.  So doing as Egbert says above will be proper.

I don't think I have seen a post here about the effects of vibration on wiring and the things that can be done to prevent, or at least minimize them.   The best marine wire/cable is made with many fine strands of tin coated copper.  Having been involved in wire manufacturing (before the jobs were sent to Mexico) our marine wire was made with  .0063 strands  The finer the stranding, the more resistant to hardening due to vibration and the more securely attached the less the effects.  Every time you bend wire you weaken it in part because you harden the copper.  ABYC has guidelines for wire mounting as well.

 

Here are a few references:

 

http://www.sailangle.com/articles/details/id/6

http://abycinc.org/?page=standardsindex

https://law.resource.org/pub/us/cfr/ibr/001/abyc.E-09.1990.pdf

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Thanks. I understand determining wire size from a device to the distribution panel, but I'm not sure how to determine the amps and wire size from the batteries to the distribution panel at the helm. Do I add the amps from every device connected to the panel? Seems this would be an exaggerated number as all the devices will never be powered on at the same time. Or, should wire size be determined by the total amps of the maximum number of devices that might be powered at the same time? The installer used 8 gauge wire to the helm with no breaker.

Chuck

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Thanks. I understand determining wire size from a device to the distribution panel, but I'm not sure how to determine the amps and wire size from the batteries to the distribution panel at the helm. Do I add the amps from every device connected to the panel? Seems this would be an exaggerated number as all the devices will never be powered on at the same time. Or, should wire size be determined by the total amps of the maximum number of devices that might be powered at the same time? The installer used 8 gauge wire to the helm with no breaker.

Chuck

 

True Chuck,

 

I think you will find that using this method will not result in a gage of wire that is impractical from either space or cost in a Bluejacket with its normally small power usage.  In any event it is easy to provide for ample over size in gage.  Since I drew the wiring diagrams, most of us have shifted to LED lighting which greatly reduces a lmajor use of 12V power. 

 

It is true that tinned wire is preferred for marine use but many (maybe most) boat manufacturers still use untinned wire without problems.  Solid wire is a no-no though due to vibration issues.  Speaking of vibration, strain relief is certainly advised in all mounted terminals and the attached sleeves of marine terminal connectors are generally good for that.  If there must be connections in the bilge, they should be in a heat shrink sleeve containing a melted sealant.

 

I also strongly recommend making a  diagram of your wiring and make several copies to insure that one is available when you need to do anything to the system in the future.  This should eliminate the rat,s nest too often found on boats that have had several owner modifications.

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If the 8 gauge wire goes from the back to the helm it does require a fuse or breaker.  For 8 gauge that would be a maximum of 80 Amp.

This doesn't mean that you can run 80 Amps through the wire.  The length would cause too much voltage drop.  ABYC recommends a max drop of 3 percent for sensitive equipment.  With an 18 foot length that would be only about 16 Amps.  

 

Tom is absolutely right about making a diagram in advance.  Numbering the wires and having a diagram helps in troubleshooting if there is a problem later.

Also a diagram forces you to think ahead and lessen the chance of last minute additions.

 

Do you have separate batteries for starting and house loads?  I like to have the starting battery only for the engine.  Less chance being dead in the water and having to call for help.

 

Egbert

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Thanks guys. I'll install a battery terminal fuse. Moving on to breaker size: is there a formula for determining the appropriate breaker size? For example, the chartplotter is rated at 1.2 amps at 13volts. It will be wired with 16 gauge wire, total length less than 4 feet. The installation manual states to connect with a 3 amp fuse. What size breaker should be used at the DC panel?

A West Marine article says:

Selecting the correct breaker size is a real problem for most custom and standard panels on the market. The issue is the impossibility of anticipating what breakers will be needed on a distribution panel, since all boats are different. Blue Sea Systems solves this problem simply. They reason that the majority of circuits onboard will have loads of less than 15A (certainly that is the case with most electronics, lights, pumps, small refrigerators, etc.). They also reason that most wire used for circuits will be at least 14-gauge, although it may be as small as 16-gauge. Therefore, they supply their panels with 15A circuit breakers throughout the panel, for the following reasons:

If the circuit uses 16-gauge (small) wire, which has an ampacity of 25A, the breaker will protect it.

15A is larger than most loads on a boat.

A small fuse can be used at the load, or a smaller breaker substituted in the panel if smaller current protection is necessary.

So am I safe using a 10 or 15 amp breaker along with a smaller fuse at the load?

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Ideally in the case of the chart plotter if that is the only thing on that breaker a 3 Amp breaker would be best.  In that case you don't need the extra fuse.  If you keep the breaker at 15 Amps the inline 3 Amp fuse should still be there to protect the equipment.

 

 

Egbert 

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Do instrument makers not still provide a proper in-line fuse with the equipment?  I generally think breakers are not the best for protecting an instrument.  They are best for major failure like an accidental short on the line and rated for the wire gage.  Not unlike house wiring with a few exceptions.  For instance, my instrument panel is fed from a single fuse/breaker and the individual instruments are protected by fuses on a separate block. Nothing against breakers but I grew up with fuses. In my experience, fuses are quicker to react than a breaker which must live to work again.

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Do instrument makers not still provide a proper in-line fuse with the equipment?  I generally think breakers are not the best for protecting an instrument. 

 

I don't think you can buy a piece of electronics for a boat (or anything) that does not have its own fuse, either in line or in the case.  I put all the electronics on my Renegade (GPS, stereo, VHF) on one circuit.  The breaker was rated to protect the wires and each component was fused to protect itself.  I definitely would not use a breaker to protect a component.  Most use glass fuses rated only 2 or 3 amps.

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Do instrument makers not still provide a proper in-line fuse with the equipment?  I generally think breakers are not the best for protecting an instrument. 

 

I don't think you can buy a piece of electronics for a boat (or anything) that does not have its own fuse, either in line or in the case.  I put all the electronics on my Renegade (GPS, stereo, VHF) on one circuit.  The breaker was rated to protect the wires and each component was fused to protect itself.  I definitely would not use a breaker to protect a component.  Most use glass fuses rated only 2 or 3 amps.

 

 

Its a few years since I needed to buy any new electronic instruments or devices for a boat or car and am glad to hear that nothing has changed in the fusing of these.  It is the only thing that really makes sense for safety of these devices. 

 

"If the circuit uses 16-gauge (small) wire, which has an ampacity of 25A, the breaker will protect it."  I assume this was a typo Chuck.

 

Most circuits on a house distribution panel have 20 amp breakers.  this is because most house wiring is 14 GA which has standard capacity of 15 amps and a 20 amp breaker will not blow unless the 14 GA wire is overloaded.  Lighting is not a problem and things like TVs have their own fuses.  Apply this same thinking to the boat and do not expect a breaker to protect an instrument powered from it.

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Looking at the various marine wire tables a 16 gauge wire can be rated at 25 Amps.  This does seem high.

However there are numerous factors that reduce the capacity of the wire.  

Does it run through engine space,

Is it 105 degree C. rated.

Are more than 1 conductors bundled.

The length of the wire and the allowed voltage drop reduces the capacity a lot.

 

I'm using for the most part 14 gauge wire, it was easier to just buy a couple of big spools of one size.  I'll determine the fuse size by the load of the equipment that is fed by the wire or whatever the original equipment fuse size is.  I don't use the inline fuses that come with the VHF, GPS and stereo  etc.  Instead the fuse blocks I use are the automotive ATC fuses.  They range from 1 A to 30 A.

 

This is my main distribution panel with nothing hooked up yet. 

I fuse panel for un-switched loads such as bilge pumps and two for switched loads for a total of 42 positions.  The breaker feeds the anchor winch.

24831923103_aafc2d46b8_c.jpg

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Egbert,

 

Sometimes it may not be good to study too much.  The AWG tables can be a bit confusing and not to be taken literally unless you know the subject.  The 22 or 25 amp rating for 16GA that you saw is for very short lengths internal to a device and the wire must be in free air (not in a bundle with other wires).  The power transmission capacity for 14 GA is about 6 amps which is ultra conservative and not to be take seriously for general usage.  The better capacity for rating for our purposes for these wires  is 15amps for 14 GA and 10amps for 16 GA. This is for the lengths of wire that we encounter in boats and when the wire is in a jacket with another loaded wire.  In a core with more loaded wires, these numbers are reduced even more.  Its all about heat that the wire may be subjected too.

 

Best not to get confused and use the simpler conservative numbers I gave for our boats.  14 GA = 15 amps and 16 GA = 10 amps.

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I know this subject can be confusing sometimes.  I recommend that the table  below be used for wire sizes on a Bluejacket.  These gages are entirely adequate for our use and the columns of 3 to 6 core jackets should make the choice simple.  Egberts decision to use only a couple gages will make it less expensive than trying to match each load to its power needs is logical.  It will be overkill on most devices needs but that is not a bad thing provided the proper device fuse is used.   As the plans wiring diagram shows, I used 10 gage for the main feed to the power panel which should handle any device or combination of 12 volt devices you might want to install.  You do not need to get into ohms per foot and line loss if you do this. 

 

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

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