Quick Beginner Questions

[Hunter]

I understand the basics of volts vs amps. My question is why not just up the volts as high as one can? What is usually the maximum for inverters to support? Is there a minimum amount of amps needed for the inverter? Sorry if these questions seem a little basic or obvious! Your help is appreciated.

[sdold]

Above 600 volts, different codes apply and the equipment becomes different and more expensive, and bigger.

Edit: I shouldn't say "Different codes", I meant the codes treat >600V differently and it's harder/more expensive to follow them.

[ButchDeal]

I understand the basics of volts vs amps. My question is why not just up the volts as high as one can? What is usually the maximum for inverters to support? Is there a minimum amount of amps needed for the inverter? Sorry if these questions seem a little basic or obvious! Your help is appreciated.

What kind of inverter are you talking about? grid tie or bimodal?

Residential Grid Tie inverters for the most part work between 350V and 600V . more to the higher end of that with the exception of SolarEdge which has a more consistent voltage from the optimizers.

They also spit out 240V AC which is the residential home voltage.

Commercial goes to higher voltages but code regulations are such that higher than 600V is not practical.

SolarEdge keeps the solar voltage at the most practical and efficient DC voltage for the inverter to converter to the required AC voltage, so higher becomes less efficient.

[Sunking]

It is the voltage and safety associated with voltage. Economics also come into play as you wil see. Think spark plugs, static electricity, lightning, and arcs. Electricity can jump air gaps and punch holes in wire insulation insulation. Rule of thumb 1000 volts per inch air gap. That is exactly what happens with static electricity, you do not have to actually touch anything, electricity will jump or arc over the air gap.

Next time you are out and about driving note power lines and look at the Insulators holding the wires. Low voltage lines up to 10,000 volts will only have 1 ceramic Insulator between the line and cross-arm. While others like 345,000 volts will have a lot of Insulators. Electric utility lines can go as high as 1,000,000 volts at 1000 amps. Come withing 20 feet of such a line, and there will be no funeral for you.

So as Steve points out electrical codes change once you step over the 600 volt line. What voltage a manufacture uses is driven by how much power is involved. Sure a Grid Tied system could use lower voltage like 12, 24, or 48 volts. However once the power goes up with a fixed voltage, current has to go up, and current determines the size of a wire along with distance. Example say you had 1000 watt grid tied system running at 12 volts with 40 feet runs to the Inverter. That would be 100 amps of current. Not only is that dangerous would require 500 MCM copper cable the size of your wrist and cost some $8 per foot and you would need 100 feet of wire and be very heavy. Use say 400 volts and you are down to 2.5 amps and can use 16 AWG wire that cost 5-cents per foot.

[lifeinthedesert]

Hi everyone, I have 16 325w solar panels, 1- midnite classic 200 charger and a outback 60 charger. I also have 6 enersys powersafe 190f sealed lead battery 13v 190ah front term. I

[jflorey2]

I understand the basics of volts vs amps. My question is why not just up the volts as high as one can?

That is often done (which is why transmission lines that go long distances use tens of thousands to hundreds of thousands of volts to transmit power.) However, in last-mile distribution, it is often safer to use lower voltages where people are nearby, to reduce the risk during a fault.

What is usually the maximum for inverters to support?

You mean for home inverters on the input side? Usually 60V is about the max they support (i.e. a 48V battery.) A few inverters are starting to support 400VDC, due to the lower current requirements, the available battery systems for that voltage, the similarity to high voltage solar arrays and the emergence of new 370V and 400VDC building power standards. For example, the StorEdge inverter uses LG Chem RESU10H batteries which are 400V.

That being said, wiring for 400V is not really something people should try to DIY at this point. The protection devices are very different, the connectors are different, the risks are different and there's just not that much experience out there in the field yet.

[Sunking]

Once you cross the 50 volt line in the sand, the rules change like no open battery buss or any exposed wiring anywhere . Completely takes it out of DIY hands. Everything has to be inaccessible like your house wiring is.

[Matrix]

Once you cross the 50 volt line in the sand, the rules change like no open battery buss or any exposed wiring anywhere . Completely takes it out of DIY hands. Everything has to be inaccessible like your house wiring is.

Is that the difference between a 24v DC system and a 48v DC system since a 48v system (like when charging) is often above the 50v line you mention?

[Sunking]

Is that the difference between a 24v DC system and a 48v DC system since a 48v system (like when charging) is often above the 50v line you mention?

No Sir, 48 volts is still below the 50 volt nominal line in NEC POV. Once you cross the 50 volt line, code rules become more strict. Example the Power Wall and other such commercial battery applications run in the hundreds of volts and you cannot access any of the batteries or wiring. The danger of higher voltages come into play and accidental contact is not tolerated. Everything has to be enclosed and grounded.