DIY switch panel (wiring) question

[Cool Beans]

So my Ranger33 has a factory custom panel at the companionway, and the PO installed a second panel inside because the original was crap. Ive since moved the newer panel and designated it for interior DC loads. I've made a new panel to replace the original and designated it for exterior loads.

My questions have to do with the panel wiring itself. The interior panel is one of these:

http://www.sea-dog.com/groups/1946-aluminum-vertical-rocker-switch-panel

It was in new condition and worked, I figured why toss it. Plus, my DC loads are small. . .but still, my calculated wire sizes are much bigger than the panels factory wiring. I have 3 lights on 14ga wire on the starboard side going to a 4 way fuse panel (1 light per fuse, 1 spare), to 12ga wire going to the panel. The panel itself is fed with 10ga wire. But, the wire from the fuse holder to the switch is only a 16ga wire on each circuit Is it because it's only a 4" run? It's soldered at one end and spade connected at the switch. . .

I need to wire together my new panel and need to figure out the wire size. The original was wired with 16ga as well. . .thoughts?

Thanks

 

[Bill Roosa]

All wires should be sized based on the max current it will handle (the fuse protects the wire so size it to pop before the wire reaches max current capacity) and the length of wire in the circuit (out and back to the batt) So even though the wires are only 4" it should be part of calculation of total length. There are several schools of thought here so "flame on guys"
I think it is bad practice to go from large to small and the back to large wire diameter. Changing the wire on some fuse holders and switches is not possible though so you have to take what they give you. I always calculate the entire circuit length then apply the graph
http://www.westmarine.com/webapp/wc...toreId=11151&catalogId=10001&page=Marine-Wire
and check any wires in between for "questionable current carrying capacity"

If you look at the graph for a while you will notice that most applications will not be materially effected by the thinner wires in the panel but you should still check that those wires can in fact handle the current.

 

[Maine Sail]

All wires should be sized based on the max current it will handle (the fuse protects the wire so size it to pop before the wire reaches max current capacity) and the length of wire in the circuit (out and back to the batt) So even though the wires are only 4" it should be part of calculation of total length. There are several schools of thought here so "flame on guys"
I think it is bad practice to go from large to small and the back to large wire diameter. Changing the wire on some fuse holders and switches is not possible though so you have to take what they give you. I always calculate the entire circuit length then apply the graph
http://www.westmarine.com/webapp/wc...toreId=11151&catalogId=10001&page=Marine-Wire
and check any wires in between for "questionable current carrying capacity"

If you look at the graph for a while you will notice that most applications will not be materially effected by the thinner wires in the panel but you should still check that those wires can in fact handle the current.

The simple answer lies in the ABYC max ampacity chart from E-11. The last Sea Dog panel I saw used 75C wire internally. This is near the minimum temp rating for marine wire. If this is 16GA & 75C wire the max than can be pulled through any circuit at any time, even for a split second, would be 15A based on the current safety standards. Sea Dog limits each circuit to 10A but this does not mean people don't shove 20A fuses in there. The entire panel is only rated for 37A IIRC...

This is one reason I mostly use Blue Sea products. Their panel breakers are bussed by a very heavy duty tin plated copper buss bar that can handle the entire main breaker rating. There are many pumps and circuits that draw more than 10A. If the Op does not have any, and won't, then the Sea-Dog panel can work..

 

[Cool Beans]

Interesting. . .15amps is the max rating for the switches and fuse holders as well on the seadog panel. . .and that WM chart is informative. I went one size higher on this first circuit for safety but now seems to be grossly over-sized. The port side I will probably go 16/14 and put each side on it's own circuit. . .that will keep each circuit for the panel at 5amps max

As for the new panel, I will size each wire according to the circuit wire size. Is it possible to daisy chain 10ga wire together with spade terminals?

Thanks!!

EDIT: The bilge pump is on it's own panel (fuse and switch). . .the rest of the DC loads are relatively light duty. . .

 

[Cool Beans]

Never mind. . .probably easier and safer to install a bus right by the panel and run the 10ga to that, then feed the individual circuits. . .

Thanks yall!!

 

[AtlanticAl]

The size of the smallest wire in a circuit, dictates the fuse to be used, with 16 gauge wire, works safely at ten amps, if you put a ten amp fuse in each circuit, it will be fine. The supply to the panel, which is ten gauge, carries, (off the top of my head) a max of thirty amps. When you are wiring something, you can use as heavy a wire as you want, the heavier the better, the safer, and the less loss to resistance, but, you must protect the circuit with the recomended fuse. its perfectly ok to use a much heavier wire that what is needed, but you can never use a lighter wire than what is needed for the load, or for what is rated on the fuse.

 

[Maine Sail]

The size of the smallest wire in a circuit, dictates the fuse to be used, with 16 gauge wire, works safely at ten amps, if you put a ten amp fuse in each circuit, it will be fine.

Actually it would not be fine on that panel. The max ampacity of the entire panel, all six circuits, is 37A.. This is usually based on what the main positive buss in the panel can handle. If you put a 10A fuse on each circuit there is a possibility of pulling 60A through a panel only designed to handle 37A. While you'd likely never see 60A it is still a good idea not to overload the panels max design limits..

A six circuit Blue Sea panel, in contrast, can handle 100A...

 

[Bill Roosa]

If you look at the table below the MW link posted above you will see that 16 gauge has a max amp capacity of 25 amps. The entire panel is only 37 amp so what I'm thinking is they cut some corners. In the end you cannot exceed either of these limits (or others we don't know about). That means you have to (gasp, horror of horrors) have to actually plan how much load you will be putting on each circuit.
Perhaps it would be easier for all of us to stop talking theory and have some numbers to assess. What are you going to put on this panel (and amp draw) specifically?

 

[Maine Sail]

If you look at the table below the MW link posted above you will see that 16 gauge has a max amp capacity of 25 amps. The entire panel is only 37 amp so what I'm thinking is they cut some corners. In the end you cannot exceed either of these limits (or others we don't know about). That means you have to (gasp, horror of horrors) have to actually plan how much load you will be putting on each circuit.
Perhaps it would be easier for all of us to stop talking theory and have some numbers to assess. What are you going to put on this panel (and amp draw) specifically?

The problem with WM is they assume a 105C rated wire, not bundled. The max ampacity for a 75C wire, single conductor, not bundled is 15A & a 105C wire 25A. This is not a max sustainable current just the peak allowable before damage to the jacketing from heat may occur. The last Sea-Dog panel I saw was not using 105C wire...

 

[AtlanticAl]

What you say about the panel being able to draw sixty amps, but only being able to handle 37 amps, could well be correct, that is why marine panels, and every other type of domestic panel, has a main braker, or main fuse, the main fuse is set to the maximum amount the panel can handle. I have re wired houses, where a 200 amp panel was required, but when you add up all the breakers in that panel, you always have more than 200 amps, a stove alone, has a fifty amp breaker, but the chances are, you will never have all four rings on high, the oven on high, and the brioler on high at the same time, so you willl never draw fifty amps on it. Its the same with this panel, you may have ten amp wire, protected by ten amp fuses, and you may in theory be able to draw sixty amps where the panel can only handle 37 amps but since it was for lights, the lights only draw about 1.5-2 amps, per light, and even if you completely shorted one of the lights out, all you could draw before the fuse is blown, is ten amps. The ten amp fuse protects the circuit, not the panel. As for 16 gauge wire being able to handle 23 amps, dont try that at home folks, when you run 23 amps through a 16 guage wire, you will get the wire to a temprature, just below the melting point of copper, so yes a bare 16 gauge wire can handle 23amps, 24 amps, will melt it the max you want to run through sixteen gauge is 13 amps, which is more than adequate for a light.

 

[Maine Sail]

What you say about the panel being able to draw sixty amps, but only being able to handle 37 amps, could well be correct, that is why marine panels, and every other type of domestic panel, has a main braker, or main fuse, the main fuse is set to the maximum amount the panel can handle.

There are many marine panels, this Sea-Dog panel included, that do not have a main DC breaker. If using this panel it would be a very good idea to install a separate DC main breaker panel..

No main breaker:

I have re wired houses, where a 200 amp panel was required, but when you add up all the breakers in that panel, you always have more than 200 amps, a stove alone, has a fifty amp breaker, but the chances are, you will never have all four rings on high, the oven on high, and the brioler on high at the same time, so you willl never draw fifty amps on it. Its the same with this panel, you may have ten amp wire, protected by ten amp fuses, and you may in theory be able to draw sixty amps where the panel can only handle 37 amps but since it was for lights, the lights only draw about 1.5-2 amps, per light, and even if you completely shorted one of the lights out, all you could draw before the fuse is blown, is ten amps.

Yes and many DIY's don't "properly" wire DC panels with a DC main breaker as many small DC panels do not come with one. This particualr panel would be well served with a DC main breaker of about 25-30A..

The ten amp fuse protects the circuit, not the panel.

Exactly, the 10A circuit fuse is there to protect the individual circuit wiring. But the main panel buss can only ever handle 37A and there is no breaker or fuse there to protect the main buss of that panel from melting down. If his loads can never exceed the 37A, which I doubt they could based on what he described he as, then he's fine. Problem is a consequent owner may come along, add a macerator, water pump or high draw bilge pump and then throw a 15 or 20A fuse in there not knowing the limit of the circuits or main buss...

As for 16 gauge wire being able to handle 23 amps, dont try that at home folks, when you run 23 amps through a 16 guage wire, you will get the wire to a temprature, just below the melting point of copper, so yes a bare 16 gauge wire can handle 23amps, 24 amps, will melt it the max you want to run through sixteen gauge is 13 amps, which is more than adequate for a light.

The MAX ampacity, even for just a spit second, is also dependent upon the insulation rating of the wires jacket. You never want to run a wire at anywhere near max ampacity based on the wires jacketing for any period of time.. This is why I dislike those Sea-Dog panels. I have had a number of customers buy them and then not be able to use them because they have multiple loads that can draw more than 10A, not uncommon on sailboats.

For example a Jabsco macerator can draw 16A and an Electro Scan type 1 MSD draws 37A for 2 minutes, many electric heads draw more than 10A. Many wash down, ballast pumps and water system pumps also exceed 10A current draw.. Rule 2000 GPH and up bilge pumps require a 15A+ fuse. DC refrigeration systems also require large fuses to handle the start up loads..

If the OP does not have any of these items and will not, as I mentioned, he will be fine.


As Bill said it would be good to get a list of the OP's DC devices/loads..

 

[Cool Beans]

I agree it probably isn't the best panel, but it was there and was fine, and the hole was already cut for it before I questioned it's construction. . .my AC panel is a BlueSea and is very well built.

I mentioned in a previous post I wanted to keep the loads around 5 amps max per circuit.

Stb. Cabin Lights (~5 amps)
Port Cabin Lights (~5 amps)
Fresh Water Pump (~6 amps)
Various Fans (~4 amps)
Instruments (~Couple amps)

I'm expecting 30 amps or so, assuming I add something to the 6th circuit. . .I was just going to fuse the panel feed wire. . .

The VHF was fused to the battery directly, and I plan on running the Stereo the same way. The Bilge Pump is on it's own little panel. . .

I like to "Keep It Simple for Savings" :dance: Fans, lights, depth & speed, pumps, and music

Thanks guys!!

 

[Maine Sail]

I agree it probably isn't the best panel, but it was there and was fine, and the hole was already cut for it before I questioned it's construction. . .my AC panel is a BlueSea and is very well built.

I mentioned in a previous post I wanted to keep the loads around 5 amps max per circuit.

Stb. Cabin Lights (~5 amps)
Port Cabin Lights (~5 amps)
Fresh Water Pump (~6 amps)
Various Fans (~4 amps)
Instruments (~Couple amps)

I'm expecting 30 amps or so, assuming I add something to the 6th circuit. . .I was just going to fuse the panel feed wire. . .

The VHF was fused to the battery directly, and I plan on running the Stereo the same way. The Bilge Pump is on it's own little panel. . .

I like to "Keep It Simple for Savings" :dance: Fans, lights, depth & speed, pumps, and music

Thanks guys!!

You should be fine. If you eventually go to LED you'll be in really good shape. Just don't go running small inverters off a 12V outlet fed by the panel.. I would run the yellow wire to "always hot" with a fuse and switch the red wire on the stereo in the panel for on/off. the yellow is your current carrying & memory wire. A DC main breaker is still a good idea..

Any connections directly made to a house battery, including the battery switch wires & VHF, should be fused within 7" of the + battery post.

 

[AtlanticAl]

A VHF should always be direct connection to the battery, this is for safety, if you lose everything else, as long as your battery still works, you will still have a VHF, even if your battery dosent work but your engine does, you can use your VHF, they should never be connected anywhere but the battery.

 

[kpgraci]

That sea-dog panel is the one I used to wire my boat. It is an inexpensive light duty panel, I'm surprised anyone would choose it for a larger boat. I only run nav lights (which are seldom on) and an auto-tiller through it for a max load of about 5 or 6 amps. I have a 30 amp fuse on each battery at the terminal and at the panel I added a 30 amp on the positive bus for panel protection. Radio shack sells in line holders for blade fuses which are easy to install in a circuit, and the ones I got have a led that lights if the fuse is missing or blown.