wire size

conntaxman

wire size, i ran #10 wire 110 ft from solar racks to panel in house I have 2 sets of wires. I was thinking of tieing 2 wires together, would that come out to about a #4 wire? i think so. I also have a small 600 watt gird tie inverter that you plug into the house current. That i was thinking of putting that with the panels and run a set of #10 to the house and use that to plug into the house current.I'll be coating all the components with marine varnish in the grid tie, and make a case for it if i do this.
oh I forgot to say that the voltage from the panels would be around 36 to 40 vdc and about i think 9 amps. their 65 watt panels 36cells each and 2 panels in series and 4 sets of the panels tied in parl.I have 18 more of these
tks
John

niel

Re: wire size

that's quite a distance with small gauge wires. for the record 2 #10 wires together would be #7. 4 #10 wires together would be equal to #4. you will undoubtedly need a single large awg wire size, but i am unsure just what it is you actually do have as you confused me a bit with, "and 4 sets of the panels tied in parl." and then further stating you have 18 more. the nec will not approve of the paralleled wires unless you have reached the sizes around #4/0. as to the wire size we do need to know exactly what kind of current will be passed. is this a total of 20 pvs with 10 strings of 2 in series? do let us know the vmp and imp of a single pv. in any case you could figure the wire size yourself with a voltage drop calculator and i have one of them in my signature line. some allow for less than a 3% drop and others go less than a 2% drop. with a long span such as yours this isn't always that easy to accomplish cheaply.

plug and play gt inverters are illegal and the legal gt inverters need to be hard wired into the breaker panel and properly sized and usually inspected.

do not varnish any electronic equipment as this could destroy said equipment and could possibly create a fire hazard.

conntaxman

Re: wire size

niel wrote: »

that's quite a distance with small gauge wires. for the record 2 #10 wires together would be #7. 4 #10 wires together would be equal to #4. you will undoubtedly need a single large awg wire size, but i am unsure just what it is you actually do have as you confused me a bit with, "and 4 sets of the panels tied in parl." and then further stating you have 18 more. the nec will not approve of the paralleled wires unless you have reached the sizes around #4/0. as to the wire size we do need to know exactly what kind of current will be passed. is this a total of 20 pvs with 10 strings of 2 in series? do let us know the vmp and imp of a single pv. in any case you could figure the wire size yourself with a voltage drop calculator and i have one of them in my signature line. some allow for less than a 3% drop and others go less than a 2% drop. with a long span such as yours this isn't always that easy to accomplish cheaply.

plug and play gt inverters are illegal and the legal gt inverters need to be hard wired into the breaker panel and properly sized and usually inspected.

do not varnish any electronic equipment as this could destroy said equipment and could possibly create a fire hazard.

.
hello niel.try this. 2 strings with 4 panels.each string has 2 panels in seires making 2 sets per string.then both strings tied together parellel.these panels are made with 36 -3x6 cells, so the vmp is 18 and imp is3.7 for each panel.
John
another question.[ i don't think it would work but!] for the p0s wire could you run will say #4 and then for the neg run a smaller say #12 and also have the Ground/neg connected to a ground rod at the panel .

Cariboocoot

Re: wire size

conntaxman wrote: »

.
another question.[ i don't think it would work but!] for the p0s wire could you run will say #4 and then for the neg run a smaller say #12 and also have the Ground/neg connected to a ground rod at the panel .

No. Wire size needs to be the same on both sides of the circuit as the current will be the same. Grounding is irrelevant to operation; it is there for safety purposes only.

inetdog

Re: wire size

Cariboocoot wrote: »

No. Wire size needs to be the same on both sides of the circuit as the current will be the same. Grounding is irrelevant to operation; it is there for safety purposes only.

And the resistance of the two ground electrodes will be so high that it will keep your system from working properly.

There have been two primary situations in which using ground rods and the earth as a return conductor have been practical:

1. High voltage utility scale power, where the current is small and the voltage drop across the ground connection is negligible.
2. Communication/signaling such as early telegraphy where the voltage drop was not an issue and the cost of running additional copper wires was high.

Make that three: cranking worms out of the ground using an old telephone ring generator.

niel

Re: wire size

ok. if i've got this correct as being 10 strings of 2 in series then the vmp is 36v and the total imp is 37a.

110ft run of #10=28.8% v drop loss.
#7 would be 14.4% v drop loss.
#4 would be 7.2% v drop loss.
#2 would be 4.5% v drop loss.
#0 would be 2.84% v drop loss.
#00 would be 2.25% v drop loss.
#000 would be 1.78% v drop loss.

hope that clarifies what you're up against.

conntaxman

Re: wire size

niel here is a pic of how im hooking them up.My controller is only good up to 55 voltsAttachment not found.

Cariboocoot

Re: wire size

That looks like four parallel strings of two in series.
If so, the array Vmp would be 18 * 2 = 36, and the Imp would be 4 * 3.7 = 14.8
For 110 foot run you are looking at a wire size larger than 4 AWG to keep the V-drop below 3%.

Options would include two sets of 6 AWG wires or a different charge controller so that they could be run at a higher Voltage.

niel

Re: wire size

see that, miscommunication again.
here's an updated overview.

#7 = 5.75%
#6 = 4.56%
#4 = 2.87%
#3 = 2.27%
#2 = 1.8%

ps- i included #3 this time because you might obtain it being it is gaining popularity for service entrance runs making it available.

conntaxman

Re: wire size

Cariboocoot wrote: »

That looks like four parallel strings of two in series.
If so, the array Vmp would be 18 * 2 = 36, and the Imp would be 4 * 3.7 = 14.8
For 110 foot run you are looking at a wire size larger than 4 AWG to keep the V-drop below 3%.

Options would include two sets of 6 AWG wires or a different charge controller so that they could be run at a higher Voltage.

.
Guess it will be a new charge controller.
tks
John

conntaxman

Re: wire size

niel wrote: »

that's quite a distance with small gauge wires. for the record 2 #10 wires together would be #7. 4 #10 wires together would be equal to #4. you will undoubtedly need a single large awg wire size, but i am unsure just what it is you actually do have as you confused me a bit with, "and 4 sets of the panels tied in parl." and then further stating you have 18 more. the nec will not approve of the paralleled wires unless you have reached the sizes around #4/0. as to the wire size we do need to know exactly what kind of current will be passed. is this a total of 20 pvs with 10 strings of 2 in series? do let us know the vmp and imp of a single pv. in any case you could figure the wire size yourself with a voltage drop calculator and i have one of them in my signature line. some allow for less than a 3% drop and others go less than a 2% drop. with a long span such as yours this isn't always that easy to accomplish cheaply.

plug and play gt inverters are illegal and the legal gt inverters need to be hard wired into the breaker panel and properly sized and usually inspected.

do not varnish any electronic equipment as this could destroy said equipment and could possibly create a fire hazard.

.
neil, how did you figure out the wire size of the 2 #10 = 7 ? the way i did it was go to the "wire gage size [found on googles] and found the #10 and x that by 2 and looked up that size for the gauge or the two together.
In your way want would be 2 # 8 wires be equal to. I found a guy with about 120 ft or 7conductor #8 wire Im offering him $75.00.
John

BB.

Re: wire size

The way AWG works, for every 3 AWG size change in wire "gauge", is a doubling (or halving) of the wire diameter. Roughly, the current capacity of the wire is based on the cross sectional area of the wire (there are some other effects, ability to dissipate heat vs surface area, insulation type, skin depth, etc... So you should still refer to the NEC or similar wire awg vs current vs conduit fill charts).

So, if you put two wires in parallel, that is the equivalent of subtracting 3 AWG steps in copper cross section.

There is another issue about paralleling copper wires for additional current capacity--Something I don't recommend if you can avoid it and NEC only allows paralleling wires for larger cable gauge sizes).

-Bill

Vic

Re: wire size

John,

Am NOT niel, but for AWG wire/cable just subtract 3 from the guage of identical wires. Wire data tables show the Cross-Sectional area of wires and cables, so you can see the effect of parallel conductors.

Vic

niel

Re: wire size

conntaxman,
as far as how i figured it out it was when i sat down and looked over awg tables along with all of the specs. you see when 2 wires are paralleled you are paralleling 2 resistances (divide by 2) and the result will correspond to the resistive value of another wire gauge that happens to be 3 numbers away from the 2 identical wires that were paralleled. there were no big complicated formulas or tricks as 2 identical wires paralleled will halve their resistance.

see for yourself,
http://en.wikipedia.org/wiki/American_wire_gauge

now looking up the resistance for #8 wire and if you divide that resistance by 7 you have the equivalent resistance and you can look up what gauge it would be or be between as often they can go in between gauge numbers.

vtmaps

Re: wire size

BB. wrote: »

There is another issue about paralleling copper wires for additional current capacity--Something I don't recommend if you can avoid it and NEC only allows paralleling wires for larger cable gauge sizes).

This is important, and needs to be emphasized. If you are going to run parallel wires, you may set yourself up for an electrical fire.

You must have a fuse or circuit breaker that is sized to protect the smallest wire in the parallel run.

Running parallel wires to increase ampacity is dangerous. Running parallel wires to reduce voltage drop is safer, just make sure the fuse is sized correctly.

--vtMaps

CATraveler

Re: wire size

For parallel wires you can check at the area: For example 10ga=10.4kcmil*2(in parallel)=20.8kcmil which is 7ga. If your panels are 110' distance then you must calculate the wire loss based on 220' of wire. I see your options as:
1. Very large and expensive wire.
2. Move the panels closer
3. Move the controroller, etc to a shed adjacent to the panels
4. More panels in series for higher voltage and new equipment.

CATraveler

Re: wire size

Whatever you do consider future upgrades that might change wiring etc. New 4 ga non UV wire is about $1/ft or $220 with a 2.3% drop.