Weak link on wire gauge plan?

[DrewLoker]

I am a planning to run 80’ to two inputs of a Bluettie AC300…from 6 460w panels…3 panels on each input for 1200w, 13a, 124v total VOC. The panels are 41v VOC each.

I understand gauge calculations, etc.

But what I am not sure about is the weak leak UP stream of the current.

The leads going into the AC300 are only 14 gauge.

Do I need to be concerned about power loss? Over heating?

I have ordered 10g wire for the 80’ runs. But is that even necessary if the leads for the input going into the unit are only 14g? I understand it is ok if each panel has 12g lead wires from the junction box, but to go from 12g from the panels, to 10g for the 80’ run, just to go the last 3’ at 14g seems problematic.

Thoughts?

Do I need to replace the leads with more robust home made wires?

Thanks!!

 

[Supervstech]

You need to be concerned with voltage drop for the 80' run.
Not the 2' into the device. 13A is no issue on #14 @ 24" but at 80' it is.
Keep in mind, dc loss is calculated for the entire run, so at 80' away, you have 160' of wire... to keep it under 3% loss, the wire run should be #8

 

[DrewLoker]

Oh boy. Bummer! $200 of 10g wire shipped out today.

When I ran the numbers, I used this guide: https://www.omnicalculator.com/physics/dc-wire-size

Basically...124v, 13.34 amps, 80ft. Recommended 11awg. The specs on the panel: VOC 41.52 (3 panels = 124.56v), 13.34a, 460w x 3 = 1380w.

Calculator above seems to indicate about 2.5% v drop.

Hopefully it will be ok. If not, are we talking about a 1/2%...or something more significant? Since I am over the wattage rating, where will I see the impact? For example, right now, I have only 1 panel hook up, and I am only seeing about 290w input. But, that is with a 12g, 60v wire that I had on hand...thus the reason I am only hooking up 1 panel.

Thanks for the reply!

 

[Supervstech]

Oh boy. Bummer! $200 of 10g wire shipped out today.

When I ran the numbers, I used this guide: https://www.omnicalculator.com/physics/dc-wire-size

Basically...124v, 13.34 amps, 80ft. Recommended 11awg. The specs on the panel: VOC 41.52 (3 panels = 124.56v), 13.34a, 460w x 3 = 1380w.

Calculator above seems to indicate about 2.5% v drop.

Hopefully it will be ok. If not, are we talking about a 1/2%...or something more significant? Since I am over the wattage rating, where will I see the impact? For example, right now, I have only 1 panel hook up, and I am only seeing about 290w input. But, that is with a 12g, 60v wire that I had on hand...thus the reason I am only hooking up 1 panel.

Thanks for the reply!

Again...
It is 160', not 80'...
Ya use the entire circuit run length... not just the distance between points.

 

[DrewLoker]

Again...
It is 160', not 80'...
Ya use the entire circuit run length... not just the distance between points.

Fortunately, I padded the measurments, so can cut the wire down to 65 or 70. Thanks for the feedback!

 

[Tomthumb62]

Not the 2' into the device. 13A is no issue on #14 @ 24" but at 80' it is.

So does that 24” also need to be replaced or does it not matter since it’s close to the beginning/end? Perhaps I’m confusing plumbing with electrical currents. A 1” section of 1/2” pipe will affect the whole line where the rest is 2” pipe. Bottleneck. Does bottlenecks exist in electrical current in the same way?

 

[Supervstech]

Won't matter.

 

[hwy17]

Actually you can rethink your plumbing concepts at the same time. A 1ft section of 1/2" pipe added to 9ft of 1" pipe still has lower total dynamic head than 10ft of 1/2" pipe. There is no bottleneck effect and the head only increases proportionate to the length that is traveling at the smaller diameter (plus some additional head for the reducer fitting too).

It works the same in electrical and plumbing.

 

[DrewLoker]

So does that 24” also need to be replaced… Does bottlenecks exist in electrical current in the same way?

Glad I am not the only one confused by this.

So is my logic completely wrong when stringing 18g inflatables to a 14g extension cord to a 12g triple tap?

I am guilty of stringing quite a few of these inflatables together…thinking the 12g wire at the wall could handle it.

And I have more for this year. 8-/

 

[Supervstech]

Glad I am not the only one confused by this.

So is my logic completely wrong when stringing 18g inflatables to a 14g extension cord to a 12g triple tap?

I am guilty of stringing quite a few of these inflatables together…thinking the 12g wire at the wall could handle it.

And I have more for this year. 8-/

Think about it like this...
Copper diameter wire has a specific resistance per foot/mm, if you have 80' of #4, and 1' #14 you have the resistance of that one foot of #14, and the resistance of the 80' #4 there is no bottleneck...
Sure, if you were trying to maximize the amps flowing through #4 or 75A let's say... THEN the 14 would be a serious issue, it would melt and fail immediately...
But for the 8A in the plans... 1' #14, and 80'#4 and all you are doing is adding the wire resistance together.

 

[DrewLoker]

Thanks for explaing it again...it makes more sense! Length AND width combined!