Wiring Question-- multiple loads on one circuit - SailNet Community

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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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Old 09-09-2010
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Wiring Question-- multiple loads on one circuit

I am starting to wire a bare boat and have a few questions-- It is a 56 foot steel ketch.

First of all I am running a heavy feed line (3% drop) from the panel to a block and then smaller lines on to the devices in that area.

Since the devices are LED lights and other new low power items, I would like to do a few on each line from the block to save wire and time.

--One approach would be to jump from one device to the next by fabricating individual cables with ends that run from one to the next. Sort of a daisy chain.

-- Another would be to run "drops" from a single main cable that run to each device. this would involve three way connectors or strip/solder at each drop.

---Or I could just run a dedicated line from the block for each .2 amp device and move on.

Any ideas on what is the most accepted?

Thanks,

Keith
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Old 09-09-2010
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I'd use terminal blocks to branch out to each device.
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Old 09-09-2010
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I would second using terminal blocks for each branch. This will simplify replacing bad wires and trouble shooting in the future.
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Old 09-09-2010
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Daisy chain sounds suspiciously like series wiring. That's like the old el cheapo Xmas lights where if one bulb went out they all went off. Not a good idea.
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No, I believe he's planning on daisy chaining in parallel.... which is the normal way multiple items are ganged on a single circuit... either on a boat or in a house.

Quote:
Originally Posted by Stu Jackson View Post
Daisy chain sounds suspiciously like series wiring. That's like the old el cheapo Xmas lights where if one bulb went out they all went off. Not a good idea.
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Sailing Dog is right. Daisy chaining in parallel.

Am now considering going to 24V across the board so the loads are even lower. The LED's and most electronics can run on either 12 or 24. Have to have 24V for the Falkon windlass and bow thruster anyway.

Hate to run 5 lines off the distribution block to .1 to .3 amp devices that are all located within a few feet of each other but that might be the best approach. Daisy chaining will require three way connections rather than the simple butt connectors to hook to a dedicated line. Some devices have only pigtails. Will have to do the terminals and heat shrink in any case -- so the only difference is the length of 16AWG cable.

Thanks,

Keith
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The problem with running with 24 VDC, is that in the US at least, finding equipment for 24 VDC systems is more difficult, and the prices are generally higher due to the lower demand and production of such equipment. If you're not based in the US or Canada, but in the EU...go for it..
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I found that most LED's and electronics are now 10-30 VDC. Since I am buying most everything new and changing out all bulbs with LED's anyway it seems less painful to go exclusively with 24V . The overhead of having to configure for and maintain both 12v and 24V is also a pain if I don't opt for one or the other.

Some items such as Caframo 747 fans are 12V only so I need to convert 24V to 12V. For low power items (.6 amp @12V for the fan) this should not be too hard. Did a search on this forum to see if anyone had asked the question of how to do it but no hits. Have heard of using a 7812 3 pin regulator in-line at the device but packaging and installation are unknowns.

Will start a new thread on this one. Several hundred people must have solved this.

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Keith-
The traditional way to wire up small loads (i.e. "portside cabin lights") is to run one breaker, one duplex power cord, and then yes, parallel all the lights on that run. So you might have a galley light aft, a bunk light midships, a v-berth light forward, all run from one circuit up the port side of the boat, with a second similar run up the starboard side.
There's nothing wrong with that really, it cuts down on the amount of work, parts, and expenses. If any one light fixture were to short out, which is the only way they could overload the circuit, it would just take out the lights on one side of the cabin. In theory, some bozo could sneak in and perhaps put 30W bulbs in where you had 10W bulbs, and overload it that way. But with LED fixtures especially...ain't gonna happen.
Remember George Carlin's routines on "Too Much Stuff!" and don't be afraid to gang several small loads on one circuit. As long as the wire is heavy enough so that the one fuse/breaker can protect the wire having multiple small loads should be OK.

The 78xx and 79xx series regulators can be problematic. They are "dumb" i.e. they regulate by consuming voltage, and they typically have a power limit around 1-1.5A assuming a proper heat sink and thermal limits. Very convenient, but also wasting a lot of power. (Spend a buck, buy one, hook up an ammeter to see what the waste is.)
Offhand I don't know what they consume but I'd prefer a second 12-volt bus with a more efficient DC-to-DC power converter feeding it up front. Or, just keeping everything on the boat at the same voltage--which can also prevent accidents.
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Old 09-09-2010
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If your lights are forward/aft and you have other things you might want to run (washdown pump, elec head, etc), it is very nice to have a realtively close tblock to pull off of. If this is just lights and/or maybe fans too, I would just keep it simple and pull a single run off the panel with dropdowns.

When wiring it, I would not ever solder. Nothing should be soldered in a boat in my opinion (I have first hand horror stories). Instead, crimp and heat shrink. It will be easier and quicker that way anyways. Double over the wire in your butt connectors when making a drop. For example, if you are using 14 for a pull, you would use a blue butt with heat shrink. Cut the wire, make the splice, and you should still have room to insert an 18/22 into the butt and still heat shrink. You can also double over teh wire as I mentioned before if you do not have room to insert both. I don't think I would invest in those Y connectors. They are bulky and awkward and in my opinion, unecessary. But do pony up for the Ancor (my preference) connectors with heat shrink for simplicity if you plan to heat shrink. The only negative when crimping with heat shrink is that you can cut through the heat shrink sometimes when crimping. Also, and the rest of the forum will get all in a huff when I say this, but if you want to save some money, you could probably get by with regular copper stranded (non tinned) inside. You can also get by without heat shrinking. I have found that interior wire in a dry environment (down below) does not usually corode when non-tinned. Exterior... you are crazy not to get tinned. But no matter what, don't solder. I pulled miles of that crap out of more than one boat now.

As far as the 12-24 v... I would not. Just keep it simple and keep it all 12v. You never know what you might want to add on to that branch one day and 6 months after putting that thing in, you won't remember which wires are 12 and which are 24. Again, just keep it simple.

My opinions.

Brian
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