Author Topic: New wiring- All home runs or zones  (Read 516 times)

P69

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New wiring- All home runs or zones
« on: July 09, 2018, 02:10:57 PM »
When designing the 12v electrical system, is it better to have home runs to each device from the DC panel or have terminal blocks in different areas (or zones) of the boat, then devices connected to that local terminal block, which has a single home run to the main DC panel?

For example, in the V berth, stbd side, I have a fan, light, two storage compartment lights under the stbd v berth.  Should these four devices have individual home runs to the DC panel or should they have a terminal block nearby, which has a single home run to the DC panel?

Attached is an example of "zones"

Thanks


Maruska

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Re: New wiring- All home runs or zones
« Reply #1 on: July 10, 2018, 09:26:21 PM »
I am all for running zones like you are showing.  I did similar things on my boat.  One example is that I ran a loop to all of the lockers and in each one installed a two terminal strip.  In the majority of the of the lockers I installed a light with a manual switch and in some a door activated switch.  This "locker light" loop even included a light inside the icebox.  Only one feeder was used on a single circuit breaker. 

The advantages are many, one of which is the stringing of much less wire than using home runs.  Additionally you will need fewer breakers resulting in a smaller cheaper distribution panel.

The disadvantages are that the one wire that you run must be sized to handle the combined loads on that circuit.  The breaker must be sized accordingly as well.  That represents a problem in itself as an issue with a 3 amp fan may not trip a 10 amp circuit that is size to protect the total circuits load.

A balance of both methods is probably your best route.  Dedicated loads for such things as pumps and electronics are probably the best as minimizing the power loss to those items is critical. 

Hopes this helps.

Dale
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Maruska

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Rudderly Confused

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Re: New wiring- All home runs or zones
« Reply #2 on: July 15, 2018, 12:22:41 AM »
I did a combination of both.  As Dale suggested, all pumps and high draw items are straight to the panel runs.  I also installed 4 - Blue Sea Systems #5025 6 circuit fuse blocks in various locations: one for the nav instruments, one for running lights, steaming lights, deck lights, and anchor light, one for starboard cabin lights/fans. and one for port cabin lights/fans.  I used #14 awg duplex from the fuse blocks to the lights/fans and instruments, and #10 awg duplex from the breaker panel to the fuse blocks.  Each appliance can use an appropriately sized fuse at the block, and total amps in the block are less than the 15 amps of the breaker at the panel.  Since I changed all my lighting to LED, the total amps isn't even close to the 15 amp breaker. 

SVJourney

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Re: New wiring- All home runs or zones
« Reply #3 on: July 16, 2018, 11:40:18 AM »
Rudderly did a little over kill on the AWG.  You can use 14ga for 15 amps and use 18ga on 5amp fuses for all lights/fans and most instruments.  Makes it easier and cheaper to wire using smaller wires.
I do love using duplex these days.  Makes the finished wiring so much cleaner and safer as you get that added sheath for chaffing protection.

Home runs versus load centers?   Home runs keep all your switches in one place.  4 load centers probably cost a bit more than just on breaker panel.  All home runs use more wire. 
Personally, I would buy a very nice panel with more breakers than I need(for later expansion).  All home runs and buy a large spool of wire wholesale.  Just a preference, both are totally above board.
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P69

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Re: New wiring- All home runs or zones
« Reply #4 on: July 16, 2018, 10:39:57 PM »
Here is a preliminary schematic of wiring from DC panel to devices. Still have to select the lights, so it is possible that i will have fewer lights than shown, depending on how bright and how far the light spreads out.  For example, I might not need 5 lights under the cabin sole for bilge illumination.

The 'zones' are based on difficulty running wires, function (running lights, bilge lights, etc..) or proximity to others.  The cabin lights will have on/off switches on the fixtures, but the bilge illumination lights will all be turned on with one switch at the panel. Same with the lights under the cockpit, port and stern lockers. Not shown is a light in the port cockpit locker that is part of the cabin light circuit and it will have its own on/off switch.  Also not shown are some 'night lights' near on the overhead  near the mast for general illumination at night.

Once I have the fixtures selected, I'll calculate the wire gauge and breakers. I'm still several months away from beginning this, so I have time to work this out.


PeteW

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Re: New wiring- All home runs or zones
« Reply #5 on: July 17, 2018, 10:15:52 AM »
Zones like you are suggesting cuts down on the number of breakers but be sure to always think it through regarding failure modes. That's why we have fuses. So if one item on the string causes an over current condition you loose everything on that string. For example if one light in your bilge goes under water due to flooding you loose all the lights. Now you are in the dark and you cant tell where the water is coming from.

I've heard stories about being marooned on a boat that is in the process of  sinking. It would be worth thinking through what circuits need to stay on at all cost.

When running multiple appliances on the same breaker figuring running and fault current gets complicated.

Whatever you decide to do, always fuse bilge pumps on a dedicated loop. A lesson I learned the hard way after my primary high volume Rule shorted and took out power to my backup Whale gulper. Had to pump out the bilge by hand. If had not rebuilt the hand pump in the cockpit I would have been up a creek.

Pete

P69

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Re: New wiring- All home runs or zones
« Reply #6 on: July 17, 2018, 10:55:10 PM »
Pete,
Interesting point about the failures with the bilge lights.  Same is true with the others that I've put on same circuit (under cockpit/in engine areas. I have that kind of fault tolerance  with the cabin lights and was looking at the bilge from a convenience perspective, not safety, as you saw it.   I'll redesign that.  I have 35 slots for breakers on the DC panel. That should be plenty with a well designed wiring layout that has some fault tolerance as you suggested.
Thanks again.



ZULU40

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Re: New wiring- All home runs or zones
« Reply #7 on: July 23, 2018, 06:55:13 AM »
There are available now 10x blade fuse blocks that incorporate a common bus
so I thought I might redesign my panel around that feature
My panel is a mess as is much of my wiring, and this would mean I could strip out some older wiring.

I think blade fuses are better than the older glass vials, and are easier to see,
and these particular fuse blocks incorporate a feature that shows a red LED whenever a fuse has blown.
Im wondering if anyone had an opinion on that.

I think that provided the connection to the bus is well made and routed this is preferable to individual wiring from the installed location of the hot bus. It does mean one must pay special attention to that particular wiring though. Still I intend to relent to individual wiring for several circuits such as the two bilge pumps fused with waterproof blade fuses locally, and the engine blower even if they are routed through the panel.

Im also thinking about emergency lighting to illuminate the bilge, the sail lockers and the engine because I have acquired a small supply of waterproof red LEDS.
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