Before doing any work, make sure you clearly understand what you are doing and to get all of the parts ahead of time. A few extra bolts and nuts is always a good idea in case you drop something.
NOTE: Your roof also must be able to handle the added weight.
NOTE: You can't do this with micro-inverters. This is a big area where SE blows away micro-inverters.
What is the Maximum Number of Panels per String?
SolarEdge will tell you 25 panels per string. Use this when ever possible. You can however normally get 27 per string and in some cases 30. I do not recommend using more than 27 or so as you may have trouble in the winter. The system simply works best with two strings with the panels equally divided per string. Adding a new string is not difficult. See below.
Adding a second string to these inverters is also a simple process. Always use the best wires and equipment and follow the electrical code. Your local electrical supply company can be an excellent source and technical resource to guide you in the right path. For example, I recommend only using 10 gauge electrical wire for your DC circuit. All AC work should be done by an electrician. You do not have to touch the AC system with an installed microfit system.
When choosing the wattage rating of your optimizers, I would go with at least 400 W. Yes our panels on the west/east roof have 300 W optimizers but with the next generation of solar panels, our 304 W CS panels will out put around 340 W on a cold winter's day. I will have to move the CS south panels to my 400 W optimizers. Luckily I can do this. When I built the system I opted for 300 W Optimizers on 250 W panels. These are okay with my Heliene 300 W panels but the next generation CS panels produce at least 10% more power on average. I could envision the CS panels with a 60 degree angle on a cold winter's day producing 360 W peak power.
When choosing the wattage rating of your optimizers, I would go with at least 400 W. Yes our panels on the west/east roof have 300 W optimizers but with the next generation of solar panels, our 304 W CS panels will out put around 340 W on a cold winter's day. I will have to move the CS south panels to my 400 W optimizers. Luckily I can do this. When I built the system I opted for 300 W Optimizers on 250 W panels. These are okay with my Heliene 300 W panels but the next generation CS panels produce at least 10% more power on average. I could envision the CS panels with a 60 degree angle on a cold winter's day producing 360 W peak power.
Tools Needed:
Hammer, chalk line, hammer drill/ nails, roof sealant, drill/bit, fittings for panel clamps, tool to open MC4 fittings, MC4 wire crimp tool, wire stripper, Voltmeter DC to pot wires. 13 mm wrenches
Many times you can use your 20V hammer drill to loosen and tighten the panel hardware. Always check that your roof mounts did indeed go into the wood rafter by tightening with a hand tool so that you can feel the torque as the bolt bites the wood. Then check it out visually in the attic.
You also need to have a basic understanding of series electrical systems. Possible Google and learn what you don't know.
Remember that there are two different clamps that hold your panels to the rails. The inner clamps and the end clamps.
I recommend using 400 W optimizers, good for 200-400W panels.
Internet to find videos to install panels, MC4 clamps, ect.
See my ladder blog and use the best ladder that you can buy.
I use a rope tied to one of my anchors to make it easier to go up on my roof.
I also lay a 1x6 board on the eve troughs to prevent damage from the ladder.
See my ladder blog and use the best ladder that you can buy.
I use a rope tied to one of my anchors to make it easier to go up on my roof.
I also lay a 1x6 board on the eve troughs to prevent damage from the ladder.
How to Add one or more panels to a string
First determine your existing string limitations. Secondly try to balance both inverters if you have two inverters.
Always be careful when working on your roof. I do not recommend working on roofs with a pitch greater than 30 deg with out proper harness.
SE have some strange power recommendations per inverter. Generally because of the superior design of the SE inverter/optimizer system there really isn't a maximum number of panels based on wattage. SE simply turns panels off when you reach the maximum of the inverter. That is a great thing and something that is needed in order to maximize your system output. I know of a system that peaks early in the day, around 11 am, 2.5 hrs before solar noon. That person's combined inverter output is 11.1 kW for 2 5000 W inverters and maintains this for about 5 hours on a good day. Her peak output power record is 103.8 kW hrs for one day. She provides power for that day to supply 6 or more houses that do not have solar panels. Her projected annual solar harvesting is a very impressive 20 MW. A local millionaire in Windsor has 25 similar 10 kW microfit systems. In fact most of her neighbours do not have solar panels.
SE have some strange power recommendations per inverter. Generally because of the superior design of the SE inverter/optimizer system there really isn't a maximum number of panels based on wattage. SE simply turns panels off when you reach the maximum of the inverter. That is a great thing and something that is needed in order to maximize your system output. I know of a system that peaks early in the day, around 11 am, 2.5 hrs before solar noon. That person's combined inverter output is 11.1 kW for 2 5000 W inverters and maintains this for about 5 hours on a good day. Her peak output power record is 103.8 kW hrs for one day. She provides power for that day to supply 6 or more houses that do not have solar panels. Her projected annual solar harvesting is a very impressive 20 MW. A local millionaire in Windsor has 25 similar 10 kW microfit systems. In fact most of her neighbours do not have solar panels.
Now that you have your new optimizer and panel you first have to install you rails that support the panel. We use rails and roof mounts from the same company. Schelter in Windsor makes the best system. You can go online to their site and pick the parts that you need.
When installing your roof anchors, first locate your roof truss and layout your mounts. I use a hammer and nail and my chalk line. I first find my ends and then every 4 feet install a mount. by using two SS bolts hand tightened to ensure that they are in the rafters and after wards visibly verify that that is true. I also recommend you add sealant just before tightening and cover the mounts with the SS flashing or Alum flashing.
Once my mounts and flashing are in, I add the rail mounting hardware and cut the rails to length. I leave at least 2 inches extra.
Next I ground the rails and add my optimizers directly to the rails. The optimizers need to be grounded to communicate with the inverters. Using the little green things to hold the nut makes this job a wiz. Every thing is in series. You can either buy pre-cut wiring complete with MC4 fittings on line or make your own. There is a 3 min video on U-Tube to show you how to use these simple, water tight crimp fittings. If you are doing it yourself, buy a good quality crimp tool and line stripper. I recommend using no. 10 gauge wires.
Caution: Before opening any existing string, TURN OFF the inverter. Wait until the voltage on the inverter is down to min. Remember, every optimizer adds 1 V so if you have 10 panels you will see 10 V. You can buy MC4 fittings on line for less than $1.50 each pair.
You system should have been installed with + and - MC4 fittings. Using the blue or black tool, open up the closest circuit, pot your new circuit to see that it is correct. If you are adding 5 panels, you should see 5 volts. You are now ready to tie in you two new wires. Make sure that you hear that click. Now go back to the inverter and measure the voltage on your circuit. You may have to open the circuit on the inverter so that you can pot it. If you only have one string that will not be required to open the circuit. The inverter will show you the voltage in the display.
Now the inverter must talk with the new optimizers. That is called PAIRING the panels. This is a very simple procedure found in the SolarEdge Manuel.
Sorry that I have not included pictures, or step by step instructions but the total procedure is very simple.
The ability to have up to 50 panels per 5 kW inverter makes SolarEdge an outstanding system. You will normally find that your roof limits you to 30 panels per inverter. What I love about SE is that when you peak out your system, SE simply turns OFF the panels that are not needed. You can mix 300 W and 400 W optimizers and 250 W and 300+W panels.
What I see in my system that 10% of the days are sunny and the system peaks early and long. 80% of the days we do not peak and could use some more panels. We NEVER exceed the 10 kW nominal rating of our system. We do not recommend that you ever exceed this when you have a 10 kW microfit system. Remember the line coming into your house is most likely limited to 200 A or around 15 kW max.
We need to maximize the output of our system to help to do our share to lower the carbon foot print of this county. Around Windsor Ontario, a roof mounted 10 kW microfit system can produce a max of about 20 MW per year. One rich guy has 25 such systems and is making about $400,000 per year after he removed all of his systems and re-installed them with SE, Schletter Rails, and the best 280 W panels that he could find. We must let the free enterprise system work, by allowing people to make a little bit of money from their solar systems so that we can lower the carbon foot print of this county. If he was on the current contract, he would make less than $200,000 per year with 25 systems. He has to pay taxes, etc. You do not get rich today. Those big wind turbine people make money also. So do the farmers who can retire on what they get paid.
retired P.Engineer of Ontario. Proceed at your own risk.
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