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ReelJerks
01-20-2010, 03:38 AM
This can help some of you in determining correct wire size.

http://beta.circuitwizard.bluesea.com/

Fin
01-21-2010, 09:16 AM
Thank you, thank you. I was just getting ready to post a ? regarding wire size. I think I found my answer at the above site.

Fin
01-21-2010, 09:22 AM
Run length.

I think of this as the combined lengths of positive and negative.

I'm trying to determine my run length on another settup I'm installing. I'll be plugging into the panel on the dash of my forward helm. Do I calculate my run length from the panel to my unit (positive) and add the negative distance? Or do I need to factor in the distance from the battery up to the control panel too?

ReelJerks
01-21-2010, 09:23 AM
Yes...total length of + & - runs.

Fin
01-21-2010, 09:42 AM
So if I've got 8 or 10AWG going up to the circuit panel (I'm not sure what I do have...will have to double check. One wire feeds the whole panel, if I'm not mistaken) and 16 AWG going from the panel to my unit (15 ft), and the calculator says I need 16 AWG for the length of the panel to the unit (15 ft) OR 14 AWG from my unit to the battery (30 ft), which do I need to use? 14 or 16 AWG?

ReelJerks
01-21-2010, 09:45 AM
If there EVER is a question as to wire size, use the LARGER size.

BASS-O-MATIC
02-01-2010, 10:17 AM
The calculator note conductor length which is just a one way length. As far as your unit location. It depends where you want to pull power from. Just calculate off that distance. I keep my sonar sepparate from the other electronics. I pull it's power from an isolated source.

ReelJerks
02-01-2010, 01:18 PM
The calculator note conductor length which is just a one way length. As far as your unit location. It depends where you want to pull power from. Just calculate off that distance. I keep my sonar sepparate from the other electronics. I pull it's power from an isolated source.

This is not correct. At least not according to ABYC or USCG standards. Doesn't matter WHERE you get power from, or where you find ground....you must add the total of the 2 directions to determine your RUN.

Edd

airmec
02-02-2010, 04:54 AM
I have seen length questioned several times and the main question is what does your formula ask for? To keep it simple almost every formula I've seen only wants a one way length adjustments for overall run is part of the calculation. This gives a general safe size for the desiered amp flow under normal conditions.
If you have proublems with electronics power feed use a shielded wire and be sure to ground both ends of the shield.

ReelJerks
02-02-2010, 05:14 AM
.....To keep it simple almost every formula I've seen only wants a one way length adjustments for overall run is part of the calculation. ....

I assumed (because it IS under this thread) we were talking about the Blue Sea Systems calculator. If you visit their calculator you will see (by placing your pointer over the required entry) they ask for TOTAL length of conductor.

Edd

mytmouse
02-02-2010, 05:30 AM
For determining the gauge of wire to run from back of boat (at battery) to a switch at helm (approx 15 feet away),

do I add 15' + the 3' from battery to ground
or
do I add 15' twice (to switch and back to battery, both are + cables) then add 3'
or
?

great link, i think when i get home I can fill in some blanks

ReelJerks
02-02-2010, 06:03 AM
Why do I feel that some of you are not reading the thread prior to asking questions?

The answer is 'Total length of the run' and that means from the power source to the device and back to the ground wherever it is.

total the quantity or amount reached by addition. (according to Webster's ll) My Funk and Wagnall is broken!

Edd

mytmouse
02-02-2010, 06:24 AM
I did read the thread (not sure if that was meant for me)....but it has confused me with prior knowledge that I thought I had.

When I did my reading to find out what gauge to use when i was installing my bait tank switch in described position, it said to measure "the length of the total positive run" which is the length of red wire from battery to switch and back to the battery (in my case 2-15' runs), it said nothing about counting the negative length, hence my confusion.* *You have stated to count the negative as well (I had never heard that until right now)...therefore I am trying to ensure I understand your suggestion correctly.* In my case the math was 30', in your case though I believe you are telling me it is 33'....I have learned something.* I actually dont think its going to matter for the 3 feet, but being an amateur in electronics I try to read before I buy and install....this somewhat contradicted what I had previously read (not sur where off top of head, could have sworn at ABYC).* I assure you I will be placing 33' in the total field as thats the worse case scenario :)

ReelJerks
02-02-2010, 07:22 AM
I did read the thread (not sure if that was meant for me)....but it has confused me with prior knowledge that I thought I had.

When I did my reading to find out what gauge to use when i was installing my bait tank switch in described position, it said to measure "the length of the total positive run" which is the length of red wire from battery to switch and back to the battery (in my case 2-15' runs), it said nothing about counting the negative length, hence my confusion.* *You have stated to count the negative as well (I had never heard that until right now)...therefore I am trying to ensure I understand your suggestion correctly.* In my case the math was 30', in your case though I believe you are telling me it is 33'....I have learned something.* I actually dont think its going to matter for the 3 feet, but being an amateur in electronics I try to read before I buy and install....this somewhat contradicted what I had previously read (not sur where off top of head, could have sworn at ABYC).* I assure you I will be placing 33' in the total field as thats the worse case scenario :)

Your scenario would be 18 feet as your total run is 15 feet from bat+ to sw and 3 feet from sw to Gnd.

Does 3 feet really make a difference? It certainly can. Especially if you are using marine wire and not automotive crap. But if you have an endless supply of money the calculator means nothing, as you can simply use whatever you like. When in doubt about wire size...go bigger. No different than breast augmentation* [smiley=yikes.gif]

If that money supply is really really big you may just burn your boat to the waterline.* :(

Edd

mytmouse
02-02-2010, 07:42 AM
"Your scenario would be 18 feet as your total run is 15 feet from bat+ to sw and 3 feet from sw to Gnd."


ugh....now I am more confused.*

I don't think the 3 feet matters in my* case as I ran 12 ga marine (which is proper per the link provided at 36'), but again I want to be sure of my install (which I thought I was sure of).* I dont want to imply like I am disregarding the 3'.

I stated 3' from "Battery" to Ground....I should have stated 3' from "Pump" to ground.* (not switch to ground)*

My ground at the switch is also 2-3', but that is not what I thought you were saying had to be counted....I though the ground to from the pump itself, not the switch....Ironically both are 3', so maybe it does not matter.

So now I need to re-ask -

My dedicated battery and pump are in back of boat for the bait tank, which is 15 feet from the switch for the pump.* From the pump there is a 3' ground to the ground block in back of boat.* From the switch there is a 3' ground from the switch to the ground block in in front of boat.*

I count 2 - 15 foot red wires (bat to swi and swi to pump)
I count 2 - 3 foot black wires (pump to gnd and swi to gnd)


Is this now 36'?* still 18?* or maybe 21? and thanks..great topic

ReelJerks
02-02-2010, 07:59 AM
I count 2 - 15 foot red wires (bat to swi and swi to pump)
I count 2 - 3 foot black wires (pump to gnd and swi to gnd)


Is this now 36'?* still 18?* or maybe 21?*

Now I got it....but dos mas questions....how are you grounding the sw? And why? (is it a lighted sw)

My thought would be; red from bat+ to sw, red from sw to pump, and blk from pump- to gnd. So I'm thinking 33 feet total run.

mytmouse
02-02-2010, 08:14 AM
Yes, a lighted switch.* thanks again, I do feel safe having the support of the link you sent, it does confirm 12 ga is all i need at 36', so good to go, but now I have confidence in my install, which is all I really wanted.* link is in my favorites now.

I am grounding the switch to the factory ground block under dash (its a blue sea ground block, just like one in back of boat, installed by North River).

ReelJerks
02-02-2010, 08:24 AM
Figured it had to be a lighted sw. Sounds like you have it locked up. Glad we got it straight.

Edd