Tag: "enphase micro-inverters"

08/06/11

  02:56:00 pm, by Jim Jenal - Founder & CEO   , 1236 words  
Categories: All About Solar Power, Commercial Solar, Residential Solar

Solar Install Step-by-Step

No doubt you have thought about installing a solar power system at your home or business but perhaps you were a bit confused about the process - how long would it take, how much disruption at your site would there be while the system was installed, and so on.

Well this post is for you - stick with us and we will walk you through the entire process, step-by-step.

Preliminary Steps…

The first step for any installation starts with an analysis of your electric usage.  We will review your bills - you might be surprised at what is hiding there - and use that to understand how big a system you would need.  Once that analysis is complete, we will schedule an appointment to come to your site.

typical customer bill
(You can click on any image to see a larger version.)

When we come to your site - home or business - we will start by looking at your service panel.  According to the electrical code, we can install a breaker for the solar power system that is 20% of your service panel’s bus rating (normally the same as the value of the “main” breaker).  Which means that if you have a 200 Amp service, we can install a 40 Amp breaker to handle the solar power system.  On a residential system, we will need a breaker that covers two slots (making it a 240 Volt breaker) so we may need to move some things around to make it all work.  In some cases, the client may need to upgrade their service panel.

As you can see, this service panel is crowded, but we can make it work.  We will also need to make sure that there is sufficient wall space for whatever equipment we will need to mount near the service panel - at a minimum an AC disconnect (so the utility can lock the system off if they need to for safety reasons).

Next, we will head up to the roof to take measurements, assess obstructions, and take photos needed to perform a Solar Pathfinder analysis.

As these images reveal, there are trees on both the east and west ends of this site.  How significantly will they impact the potential performance of this system?

The Solar Pathfinder is a simple and elegant tool for determining how much shading a given location receives over the course of the year.

As you can see in this picture, those trees that we noted previously really do encroach on this site.  We will put the picture into the computer to see just how bad this might be.

The computer program allows us to trace the shading objects on the computer screen and from that, the system determines shading angles and the overall amount of shade at that location.

For installations done in SCE territory, we need to do an analysis at four corners of the proposed array.  The program then averages those out and calculates an overall shading summary.

Here, the final shading value is below 80% - a very low value indeed.  Once-upon-a-time, we would have told this potential client that solar would simply not work on their roof.  However, with the advances being made with micro-inverters, we can now successfully install productive systems where substantial shading - particularly shading like here that will sweep the array in the morning and the evening - is present.

We will take all of this information and provide you with a comprehensive proposal that will list all of the components we are proposing to install, show you how much of a rebate you will receive from the utility, estimate the amount of energy your system will produce and calculate your return on investment.  (We’re sure you will be pleased with those numbers!)

Once we have a signed contract, we can move on to the next phase.

The Installation Begins…

After we have pulled the necessary permits, we will be ready to start work on your project.  For a typical residential system, we will usually be done in two or three days.

We begin by installing the necessary equipment on the ground - making space in the service panel for our breaker and mounting the required AC disconnect.  We will also include a performance meter on the disconnect because we are using a micro-inverter system.

Another consequence of using micro-inverters on this project is that there is no large string inverter to mount on the wall.  However, we do need to add a relatively small subpanel where our array branch circuits can land.  They will each be protected by their own circuit breaker and then the combined output will be routed to the service panel breaker through the AC disconnect.

While that work is underway, we will also be laying out the attachment points for the array.  It is important that our attachments - 6″ standoffs typically - are directly bolted into the roof rafters.  On this particular project that was even more critical, since the client had a vaulted ceiling and any error would be immediately visible!

Once the attachments are secured to the roof and flashed, we are able to mount the rails.  The rails - from Unirac in this instance - click into the standoffs.

Then we can attach the Enphase micro-inverters to the rails and run a continuous equipment ground wire to bond all of the inverters together.

This picture shows all of the rails and micro-inverters in place, with all of the grounding wires connected.

Now all we need are the Sanyo solar panels.

Co-Founder Brad Banta helps off-load Sanyo solar panels and our crew on the roof moves quickly and efficiently to install them.

This array is completely invisible from the street, but we take great pains to make the installation as neat and precise as possible.
That attention to detail - even when it will be unseen by the client - is one of the hallmarks of a truly professional installation.

Now that the installation is complete, all that is left are some final details - signage and inspections - before this  system can go live.

As always, the system sailed through inspection and the client was thrilled to have their solar power system up and running… for the next 25 years!

We noted at the outset that this site was severely affected by the presence of trees on both the east and west sides.  As a result, we decided to go forward with this installation using micro-inverters.  But the question remains - do the micro-inverters really make a difference?

We monitored the actual energy production from this system for a year and compared it to what SCE’s rebate calculator predicted.  Our final image shows the results.

In this graph, the bright green bars show the actual energy produced where the lighter green bars show what was predicted.  In every month except October, the actual production exceeded - and in the winter months far exceeded - the predicted system output.  In fact, the overall energy yield for this system was more than 15% above the predicted yield.  That means more savings every year, which translates into a faster payback on the client’s investment and more money in his pocket for years to come.

So that’s it - total install time was 2.5 days.  (It actually took longer to pull the permits than it did to do the job - but that’s a topic for another day.)

We hope this answers some of your questions about how a residential solar installation happens from start to finish.  If you have any questions that we didn’t answer, please leave them in the comments.

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Jim Jenal is the Founder & CEO of Run on Sun, Pasadena's premier installer and integrator of top-of-the-line solar power installations.
Run on Sun also offers solar consulting services, working with consumers, utilities, and municipalities to help them make solar power affordable and reliable.

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