There's quite a lot of labels you have to have now for things on your solar array. This is for a disconnect switch and a sticker that has to go on there. For your inverters, when you're inspecting a system, it's good to have the spec sheet for the inverter that you're supposed to be inspecting. There's not a lot necessarily to inspect other than it's installed to the manufacturer's instructions, if it's a grid tie, it has to be UL listed to 1741. The microinverters, those are up on the roof, a little bit harder to inspect those, however, the wiring is coming down from the roof for microinverters is AC wiring is not DC. The most of the modern ones do not have a transformer. They are sometimes called transformer lists, sometimes called I'm grounded in the sense that you're not grounding it to the plus or the minus on the DC side, so that's simplified the wiring a bit. There are inverters that are pure grid tie, and there are ones that can deal with battery banks. So this is a string inverter, so you have series wiring up there on the roof feeding usually fairly high voltage DC to the inverter like 400 or 500 volts DC to the inverter, and this is just a couple of diagrams of the difference between a grounded system where you're grounding one of the DC conductors versus ungrounded. From an inspection perspective, something is grounded generally the grounded conductors is white just like it would be in an AC system white or gray, and ungrounded not supposed to be using white. For one of those, usually there could be black and red perhaps on the DC side. Battery inverters, those systems can involve other pieces of equipment like charge controllers and additional disconnect switches between say the battery and the inverter, the battery and the charge controller, the array and the charge controller. There are also so-called AC coupled systems where the battery inverter is simply feeding a critical load panel, and when the grid goes down it disconnects from the grid. Probably the most important feature of inverters is they have to disconnect from the grid when the grid is down because that's to protect alignment if they're working on the wires. Microinverters says there's rules in the code about what to do about that DC wiring coming down from the roof. Well, recent microinverters, you don't have that. You have AC wiring coming down from the roof. This is a picture of some microinverters, they're up there behind the solar modules. When it comes to grounding, they're usually attached to the rails of the system in such a way that they're actually electrically attached to. So that's how those get the equipment grounded, it happens in that way with the microinverters. AC disconnects switches, there's nothing really that special for those other than the normal rules of having to handle the amount of current and voltage that is coming off the inverter. All disconnect switches have rules about accessibility. They need to be readily accessible and there are some exceptions to that depending on where the inverter is, but generally disconnect switches, you got to have them in a place where you can shut them off easily. More about labeling, not switch. Rapid shut down. So this is really the new news in 2014 as this rapid shutdown is required, if you have DC wiring coming down from the roof which if you have a string and wire, that's what's going to happen. You're going to have high-voltage DC wiring coming down from the roof, and so the idea here is you want to be able to disable that, get the voltage off those wires if first responders have to do something. If they come along and they say pull the meter, normally they come and they pull the meter, if there's a fire or something they have to deal with and they are assuming all the electricity is now down. If there's sunlight, there's going to be DC voltage on those wires coming down from the roof, open up the circuit somewhere up there at the roof level. That means there's another switch or button hanging on the wall somewhere hopefully next to the meter. The first responders can push the button or flip the switch. Now the good news for residential ones, that's an extra piece of equipment a lot residential systems are now using microinverters, and microinverters actually satisfy rapid shut down without any extra equipment because as soon as a utility power is lost, the AC output of the inverter shuts off immediately. So there's no voltage coming down from the roof on a system with microinverters. So you don't need an extra piece of equipment. But you can get it if you need it, it's out there, there's manufacturers making it. A lot of times the inverter manufacturers have them. Another device which is becoming popular which is the DC optimizer, which is often used in conjunction with the string inverter. A lot of the newer ones will reduce the DC voltage on the wires coming down from the roof to near zero. There's even once it will reduce the voltage within the array too. So these little boxes can go long ways to making sure that if someone is up having to deal with wires on a solar array even if it's sunny out, they won't get zapped. When it comes to interconnection, there's really three ways that it gets done. Either you're connecting on the load side which means you are feeding a breaker and that means circuit box. Or you are going past somewhere between the circuit box in the meter and doing a supply-side connection. Or if for a bigger system, you may even have a dedicated electrical service for a bigger system. So there's various ways of interconnecting to the utility power and there's code rules for all those. The main rule for connecting into your circuit box has to do with how large of a breaker can a solar electric system feed. Because now if you're feeding a solar electricity into your circuit box and you're feeding from the utility, the busbars in that box can handle a certain amount of current and you do not want to put more current in there than it can handle. There are some rules about that limits, the size of the solar electric system that you can feed into a given circuit box, and there's a little formula for that. Take a 125 percent of the inverter's output, so that's the amount of Amps, add that to the main breaker reading, if that is less than a 100 percent of the busbar rating, then you can put a breaker anywhere in that box and feed it with your solar. If that sum is greater than a 100 percent of the busbar rating and less than a 120 percent of busbar rating, you can still put a breaker in that box. But it's got to be at the furthest spot from the main breaker. That's just to prevent localized heating of your busbar. What do you do if the sum is greater than 120 percent of the busbar rating? Well, either you have to downsize the main breaker which sometimes you can do that, or you got to do some other connection. That's something that the designer should have checked out and sized appropriately. This is a good thing to inspect. Is there a label on the breaker that is being fed by solar? A lot of times people forget to put that on there. That's one of the more important labels to have because anybody in the future needs to know that. There's some breaker being back fed from another source of electricity. Now if you can't feed a breaker in the circuit box, you can still do what's called a supply-side connection, where essentially you're going to interconnect your solar array between the circuit box and the meter, so now the size of the busbar doesn't come into play. There are code rules about how to do that, for example, you need have a disconnect switch in that situation that's specific to that connection. A lot of times we run into is not so much that the circuit box is too small from an outerbridge perspective, but there's just not a spare spot in there to put a breaker. The AC disconnect switch if you're doing a supply-side connection, you've got to have a switch that has the right voltage rating on it, the right current rating on it, you've got to have one that has fuses in it for that particular connection.
