Category Archives: commercial-solar

Structural Engineering is a small but critical part of the engineering for a rooftop solar project.  It can make or break the feasibility of the project or have significant effects on the system size and cost of racking. 

In the first part of this two-part article, I covered the roof membranes and roofing systems commonly used in commercial and industrial (C&I) buildings. Roof identification is important because this information drives other design and engineering...

Commercial and industrial (C&I) roof-mounted solar photovoltaic (PV) systems present a unique set of engineering challenges and technical risks. Some commercial roof considerations—such as the structural analysis and roof loading plan—apply...

With 21 engineers between our NJ, CO, and CA offices, we have unmatched bandwidth to design your solar & energy storage projects fast. What does that mean for your project? Quick turnaround time from quality engineers means you can complete your...

Its common knowledge that Aluminum (Al) conductors cost less than Copper (Cu). But how big is the difference in price? The answer may shock you.

Our first article 2014 NEC 690.12 Rapid Shutdown for String Inverters on Flat Roofs we explained the basics of implementing a rapid shutdown system using string inverters on a roof.  In that article, we gave a simple example of a single array.

The 2014 National Electric Code added a new section of code 690.12 requiring "Rapid Shutdown of PV Systems on Buildings".  Below is the first of 1 of 2 articles we put together to help you understand this code (here is the other: 2014 Rapid Shutdown...

In a previous article “The 120% Rule Explained – 2011 NEC 705.12(D)(2)” we clarified the philosophy of the 120% rule for load (supply) side interconnections of solar PV systems. The 2011 code was clean, understandable, and easy to safely apply.

480 to 208 Transformers are commonly needed to step down 480V inverters for 208V services. Unfortunately electrical rooms are often crowded with existing equipment. Sometimes there isn’t room for a transformer, so we are often forced to locate the...

Here is something that’s crazy, and yet we completely understand why they did it. Some evil genius put duct tape around the vents of a NEMA 3R transformer. If this transformer is heavily loaded it runs the risk of overheating, but at least snow cant...

Everyone knows about the 120% rule, but not everyone understands the situation it is trying to protect against. This article will explain Pure Power’s philosophy on the 120% rule.

Pure Power engineered a rooftop solar PV system with an innovative new method for mounting string inverters. The inverters are mounted on strut stands directly over cable tray, and the AC and DC wiring is all neatly and compactly run in the cable...

Im not sure which of these photos is the scariest...

Thermal (IR) cameras are a great tool for preventative maintenance and inspection of your PV system. With a little thermography “know-how” and some image focusing, problems can be discovered quickly before they create a fault or safety hazard in the...

On this system, the installer stacked ballast so high that it shades the modules at noon of each day. Why would anyone use a hollow block for ballast?

This photo is an excellent example of an inverter installation on the roof. Keeping the inverters next to the array allows the unfused string wires to be kept at a minimum length, increasing safety. Notice how the inverters are tilted to the north...

I appreciate Shoal's new arc fault technology as shown in this advertisement, however I was shocked to see the photo of a man standing on PV modules.

When you select the wrong transformer enclosure rating, moisture will get into the transformer enclosure and cause faults. NEMA 3R transformers are effective at keeping out rain, but sometimes no snow drifts.

In a recent project we were able to value engineer a DC combiner feeder by running an overhead line rather than trenching an underground duct bank. The feeder would have been a 175 feet underground duct bank routed across a high traffic driveway...

Ground Mounted Solar Projects

Municipal Zoning/Planning Approval (566 Municipalities in NJ) All land development activities in the State of New Jersey require some level of Municipal approval. Typically, solar farms require site plan approval from...

Here is a video I found on the internet, produced by American Apparel. I figured I would share it as an example how NOT to clean PV panels.

Many roofs are designed to support thousands of pounds of HVAC units and large air handlers, so the additional weight of an inverter is feasible in many cases.

Be careful with Aluminum Conductors

The cost savings of Aluminum conductors is too good to ignore. Both the engineer and the electrician must respect the differences between copper and the less forgiving aluminum. However, if designed and installed...

When deciding what size and quantity of combiner boxes to use, always remember to use the full capacity of what you are buying.

Value Engineering Combiner Boxes

You can save up to 25% on combiner boxes and DC disconnects switches if they are properly designed. It is well known that you size equipment for 1.56x of the short circuit current. However, with certain solar...

Over the years, we have seen just about every combination of equations and numbers used to calculate the NEC required values on a DC disconnect switch. NEC requires these values to be calculated and shown on the DC disconnect switch, but it doesn't...