Inverter distance questions

[mschulz]

So I have this narrowed down to what I want to do and now trying to figure out where to put it all. I have the option to install panels on top of a storage shed 75 feet away from my cabin (400SqFt). Doing this I would be able to have the panels on the roof of the shed and all the batteries, charge controller, switches, inverter and generator in the shed and away from my cabin.

My question is if I were to use the inverter ( Magnumn 1500W 24volt) and convert to 120 volts and send it 75 feet to the service panel over 10AWG wire, would that be that much of a problem (2.25 volts lost). Especially if I am only needing 300-500 watts at a time in the house.

[Mike90250]

use your highest voltage, for the long distance runs. Since I don't know what your PV voltage is, I can't advise.

[mschulz]

use your highest voltage, for the long distance runs. Since I don't know what your PV voltage is, I can't advise.

Highest volts and lowest amps right?

example : 120volts AC at 10 amps would be better than running 150volts DC at 40 amps right?

[Naptown]

use your highest voltage, for the long distance runs. Since I don't know what your PV voltage is, I can't advise.

This is the question and without the answer as to what you have on the roof and what kind of controller you are using it is hard to tell what is best.
I have run Arrays up to 700 feet from the inverter by sticking with DC and running high voltage.

Your scheme will work with the exception that at night if you want to turn off the inverter to save the standby losses you have to go out to the shed.

During the winter if you are there it would be better and more capacity in the batteries to keep them nice and warm in the cabin with you.

[mschulz]

This is the question and without the answer as to what you have on the roof and what kind of controller you are using it is hard to tell what is best.
I have run Arrays up to 700 feet from the inverter by sticking with DC and running high voltage.

Your scheme will work with the exception that at night if you want to turn off the inverter to save the standby losses you have to go out to the shed.

During the winter if you are there it would be better and more capacity in the batteries to keep them nice and warm in the cabin with you.

I haven't bought any of the part yet as I am trying to make sure I do this right the first way. My plan is to buy 250-300 watt grid tie panels and run them in series to maximize voltage and run that into a Midnight Solar Classic 150. My PV watts will be 900-1200 watts. Batteries will be around the 350-400 AMP hour in 24 volt or 225 AMP hours at 48volts. I would like to go with one of the Magnum inverters as they hook up cleaner (and safer) than a bunch of low watt inverters. Will have have the remote switch inside to turn the inverter on and off.

I would love the batteries inside to be nice and warm, but that just isn't going to happen and will be in an insulated battery box with a vent fan when charging. My first idea was to install the panels on the roof and have the batteries in a box in the breeze way and the CC, Inverter, etc on the wall, but that is messy and would be taking up space. Having it in the shed gives it a nice dry open area with lots of room along with me not having to drill holes in the roof of my house.

[Sunking]

I will give you a hint. A utility is required to supply you at a voltage of +/- 10% nominal.

So at 120 volts nominal what is the range and are you within that range?

Now for low voltage you want to keep losses under 3%. Very hard to keep low voltage losses low, easy and cheap to keep high voltage losses low. That is why utilities use very high voltages.

[mschulz]

I will give you a hint. A utility is required to supply you at a voltage of +/- 10% nominal.

So at 120 volts nominal what is the range and are you within that range?

Now for low voltage you want to keep losses under 3%. Very hard to keep low voltage losses low, easy and cheap to keep high voltage losses low. That is why utilities use very high voltages.

I get the whole higher the voltage the better thing. What I do not know is if the distance from the shed at 120 volts from the inverter is going to drop to low to use. What I have found with the wire calculators is that:

10AWG, 120v at 15 amps run 75 ft would be a 2.25 volt loss or 1.88%
8AWG, 120v at 15 amps run 75 ft would be a 1.14 volt loss or 1.18%

I am asking you guys as the pros, is that acceptable or are there $$ getting lost during that 75ft run. Remember I do not need to do this as cheap as possible, but I am only going to use 1500 watt hours/ day on a very high day, most days will see 500-800 watt hours.

[Naptown]

You are well within voltage drop limits with the #10
Just remember that any motor load will increase watts to compensate. Resistive loads will decrease watts

[mapmaker]

I have the option to install panels on top of a storage shed 75 feet away from my cabin (400SqFt). Doing this I would be able to have the panels on the roof of the shed and all the batteries, charge controller, switches, inverter and generator in the shed and away from my cabin.

My question is if I were to use the inverter ( Magnumn 1500W 24volt) and convert to 120 volts and send it 75 feet to the service panel over 10AWG wire, would that be that much of a problem (2.25 volts lost). Especially if I am only needing 300-500 watts at a time in the house.

Very smart approach... the panels are close to the electronics, and the 120 volt AC travels the 75 ft distance. Plan ahead for future growth and use the heaviest wire you can afford... at least #8 gauge.

Will have have the remote switch inside to turn the inverter on and off.

Be sure to run two conduits between the power shed and the house... one for the 120 volt AC and the other conduit for battery monitor and remote control of the inverter and controller.

My plan is to buy 250-300 watt grid tie panels and run them in series to maximize voltage and run that into a Midnight Solar Classic 150. My PV watts will be 900-1200 watts.

If I understand your plans, the panels and electronics will be near each other at the power shed. Therefore you do not need to maximize the voltage between the panels and controller. The Classic will be more efficient and run cooler if the input voltage is lower. If your panels have a Vmp of 30, put two in series for a 24 volt battery or three in series for a 48 volt battery. If you want 4 panels with Vmp=30, configure them as two parallel strings with two panels (in series) per string for a 24 volt battery. If you want a 48 volt battery, you would need either 3 or 6 of panels with Vmp=30.

--mapmaker

[Sunking]

I get the whole higher the voltage the better thing. What I do not know is if the distance from the shed at 120 volts from the inverter is going to drop to low to use. What I have found with the wire calculators is that:

10AWG, 120v at 15 amps run 75 ft would be a 2.25 volt loss or 1.88%
8AWG, 120v at 15 amps run 75 ft would be a 1.14 volt loss or 1.18%

You could use 12 gauge which is not only safe @ 15 amps, but acceptable losses of less than 3%. From the utility 120 volt service is anywhere from 108 to 132 volts or +/- 10%. That is what I was hinting at trying to make you answer your own question.

[Mike90250]

Highest volts and lowest amps right?

example : 120volts AC at 10 amps would be better than running 150volts DC at 40 amps right?

Bad example - the watts are different.

But with the other answers, I think you are on the way.

[Sunking]

Highest volts and lowest amps right?

example : 120volts AC at 10 amps would be better than running 150volts DC at 40 amps right?

No sir not a correct or equal statement. Watts have to be equal in both statements to be true. Watts = Volts x Amps. 120 volts x 10 amps = 1200 watts. 150 volts x 40 amps = 6000 watts. 1200 does not equal 6000.

[paulcheung]

Goodmorning, Since you guys are talking about wire size, I have a question, how many amperes I can safely draw from a 4mm size wire? I am not sure what gauge that is, but the cable it self clearly printed 4.0mm. it is a 3 core cable. Can I safely draw 4400watts on 240 volt AC for 90 minutes?

Thanks

[russ]

distance?

proper cable name - description from the cable?

application?

[Sunking]

4 mm is just slightly larger than 12 AWG. so around 25 amps is tops. At 19 amps you are good to go.