DC panel wiring

[SeaBreeze]

I’m not going to be on the boat for a few days, but am trying to buy all the supplies I need for a little project now. I’m hoping someone can help me by identifying some wiring on the DC side of the panel. Getting a clear understanding will help me get my stuff together now and save me a trip or two (it’s always two) to the store to buy the one thing I forgot. Looking at the panel when open and laying on the chart table, I recall seeing what looks like like a buss-like configuration of red wires on the right (forward) side of the breakers. Are these red wires leading to a common (+) or (-) tie point somewhere or to the (+) or (-) side of loads? I’m asking because I associate red wires with (+). But it seems odd to me that their connection to the right side terminals of all the breakers seems to be buss-like. Perhaps more like jumpers from the right side of one breaker to the next. And if I remember correctly there are red wires connected to the right side of ALL breakers, even the unused ones. Or am I misremembering what that wiring looks like? Next question - where behind the panel would be the best tie point to add a (+) wire and add a (-) wire to be connected to the new load,with (+) going through a spare breaker of course? Bottom line is - I know I need to wire from (-) to the black wire on the load, then from the red wire on the load through the breaker to (+). Just would prefer to find a (+) & (-) points behind the panel instead of sourcing (+) & (-) at the battery posts. Thanks for any help you can provide.
Rick
Sea Breeze
2003 C350

[R.B.]

Hi Rick,
I am also away from my boat and without a picture, so I am just going by memory. Use a Voltmeter to check your connections ahead of time to be sure. But I believe you are correct, all of the breakers on the swing out panel are wired to the positive and are red. The black wired busses mounted on the back wall of the cabinet are the negative busses.

I typically run new wires behind the panel, +ve to the unused breaker and negative to the Black bus on the wall

[KenKrawford]

Rick, when you're connecting to the negative (black wires) bus mounted on the hull make sure you're using the one on the right, not the left. The smaller negative bus bar on the left side is for the 120 volt AC system. The 12 volt one is on the right. If there isn't an open spot on the bus bar, you can unscrew one of the ring terminals and double up.

[BillBerner]

Rick -

Guessing you’re knowledge of elect. is basic, so I’ll go into some detail. Apologies if I underestimated.

The Line side (Supply, or put another way, power in) of the hots are, as you supposed, bussed for bringing power to the breakers. The wire feeding them is coming from the load side your battery selection switch.

You’ll want to connect the hot wire (red) of the load your adding to the load side of one of the spare breakers. Make it pretty and tie wrap it to the rest of the distribution bundle.

The ground wire (black) should connect to the boat ground buss on that is mounted to the inside of the hull, or a board attached to it, behind the electrical panel by the right edge of the cutout for the panel. There are 2 busses there. 1 for neutral of the 120v system, The other is ground for the 12 volt system. Make sure you connect to the buss for the 12v system, not the 120. Easy way to differentiate is that the zinc saver ground is connected to the 12v ground buss. Ground wires (green) of the 120v system are probably all connected there as well - can’t recall for sure.

Important! Make sure the device your adding is rated below the amperage of the breaker you are connecting it to. Can’t recall the rating of the spares. It’ll be noted either on the tip of the switch, or on the back side of the breaker. Calculate amperage by dividing wattage by 12 (a=w/v).

Hope that helps

[SeaBreeze]

Thank you
Thank you
Thank you
With your help I may now have a once in a lifetime chance of finishing a project without stopping mid project to go buy that one part I didn’t account for when planning the job. (In this case, a ring connecter for that negative buss)
Rick Parish
Sea Breeze

[SeaBreeze]

Well it looks like I need a little more help. The LED on the switch panel next to the LP Solenoid switch worked for over a year after we bought our 2003 C350. One day it just died. Looking at the back of the panel and the mounting method it appears to have been the original LED. I replaced it with a 12vdc rated LED from Radio Shack. It lasted a few minutes and burned out. I replaced that one with a 12 vdc rated LED from Newark electronics. It lasted about 10 minutes. I think I’ve done the wiring correctly. Wiring is as follows: LED red (+) wire to load (aft) side of LP breaker through the LED to LED negative wire to 12vdc common on negative buss. I measure 12.6 or 13.4 vdc from the load side of the breaker to the negative buss depending on state (charging or idle) of the Charles battery charger. LED off when breaker off. LED on when breaker on. But LED burns out before I’ve finished cooking breakfast. Suggestions would be most appreciated.
Rick
Sea Breeze

[leigh weiss]

Add a 1000 Ohm 1/8 or1/4 watt (Brown,Black,Red) resistor in series in the positive lead of the Led to limit the current and drop the voltage. This should work to keep the led happy.

[pjr]

Sounds good. Leds need a current limiting resistor or equivalent to prevent excessive current that would burn them out
Many small leds run at 20 to 50 mA (,02 to .05 A) 12.5V / .02A = 625 ohms. So a 1,000 ohm resistor would be a good starting point.

[SeaBreeze]

Thanks guys. With no local Radio Shack finding one 1k resistor is turning out to be a challenge.
Rick
Sea Breeze

[Guinevere]

Rick -

I'm afraid you may be on the wrong path here.

If you bought an LED assembly (i.e. not a bare LED but a ready to be mounted LED indicator) and it is rated at 12 VDC, it will already have a suitable dropping resistor included internally in the assembly.

Here's an example one at Newark: http://www.newark.com/dialight/559-0103 ... dp/30K2946.

If this is what you had (before it burned out), you bought the right thing, no resistor is needed, and the problem lies elsewhere.

Looking at the 12 VDC schematic (on page 37 of the 350 Owner's Manual) the LED indicator is wired from the switch (12 VDC when on) to 12V GROUND. If your LPG solenoid is working correctly then I'd check your LED wiring to make sure it isn't wired ACROSS the switch which would cause it to sync all of the current required to energize the solenoid when the switch is turned on.

Other possibilities include flyback from the solenoid coil but I would hope it has an internal diode to control that.

Good luck!

Bob

[SeaBreeze]

I’ve got the LED problem with burning out LPG panel lights solved and added another LED so I know when pressure water breaker is on. I sometimes forget to turn it off. So if anyone has problems with panel mounted LED’s this may help you. Thanks to everyone who provided advice, particularly Guinevere & Brisa for your emails. Leigh, do you want me to return the diodes and resistors you sent me? Having installed LED’s in all the 12v cabin lighting fixtures with no issues I didn’t realize the significance of the term “forward voltage”. That wasn’t a term I encountered when selecting them. If you plan to select a panel mount LED, look for the forward voltage rating. If it’s 12vdc you don’t need a resistor in series with the (+) lead if you have 12vdc system voltage. If the LED’s forward voltage rating is anything less than 12 vdc, you need to add a resistor. There is a formula to calculate the needed resistor value. Best explaination I found was at www.baldengineer.com/led
Rick
Sea Breeze
Currently at Little Harbor
Tampa Bay

[leigh weiss]

Rick,
Glad you solved the problem.
If anyone else needs the parts, you could pass them on or just hold on to them for the next project.

Cheers,
Leigh