As interest in stationary energy storage grows, it is tempting to assume that energy storage systems (ESS) in general—and battery energy storage systems (BESS) in particular—will follow a similar growth curve as solar photovoltaics (PV). In this...

Power engineering is a broad electrical engineering field that covers all aspects of the bulk electric power system, including power generation as well as transmission and distribution. As a full-service engineering firm specializing in photovoltaic...

Effective grounding in photovoltaic (PV) systems is the creation of a low-impedance reference to ground at the AC side of the inverter—or group of inverters—that is designed to be compatible with the distribution network’s requirements and existing...

Pure Power performs many types of power system studies, and the Arc Flash Study may be the most important because it is all about worker safety. However, since it’s not always a code requirement and doesn’t have a direct impact on generation, it is...

Pure Power performs many types of power system studies, and the Arc Flash Study may be the most important because it is all about worker safety. However, since it’s not always a code requirement and doesn’t have a direct impact on generation, it is...

EV chargers currently come in three different models: Level 1, Level 2, and Level 3. Level 3 is also commonly known as Direct Current Fast Charging (DCFC). In Level 1 & 2. the EV is connected to AC power, 120V or 240V, and a battery charger in the...

How does Pure Power keep its stellar reputation year after year?  Simple… our team stays together and gains more experience every year.

NEC 2017 brings with it some advantages and disadvantages. The new rapid shutdown rules that require MLPE are the biggest change (that is an advantage for safety, but disadvantage for project costs).

Pure Power is looking to add more A-Players to our team. However, they are few and far between, so we need your help! If you refer us to a candidate and we hire them, we will send you a $1,000 Amazon gift card!

Developers of solar projects are facing the question…what are you doing to prevent the issues Walmart encountered?

There are many things about EVs that are similar to an internal combustion engine (ICE) powered vehicle, but there are also some important differences and some less understood equivalencies. In this article, I will discuss some of these comparisons...

The ac collection system in commercial roof-mounted PV systems generally extends from the inverter ac output terminals to the low-voltage point of interconnection (POI). The exception is when the system interconnects at medium-voltage levels, in...

We often see the 3 mistakes below being made on many solar projects. These mistakes have an effect on the long term operation, quality, and safety of the system. Perhaps since they don’t have an immediate effect on project closeout, it's not on the...

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...

This is a simplified version of my previous article on the new Rapid Shutdown codes taking effect on January 1, 2019. For those interested in the technical details of the code, refer to 2017 NEC 690.12 Rapid Shutdown – Important Changes.

The 2017 National Electric Code (NEC) dramatically changes the requirements for "Rapid Shutdown of PV Systems on Buildings." Half of the states already adopted NEC 2017 and several more will in the next few months (such as NJ and CT), so you can’t...

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...

We were called out to investigate a performance issue at a site, and were shocked to see this wire management. We suspect the AHJ made this contractor install physical protection after the strings were installed, which is why the contractor cut the...

Just when I thought I have seen it all... Notice the mid-clamp that was never attached because the module was raised off the rail. Scary!

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.

While conducting O&M on a Satcon 250kW central inverter, we noticed this fan with an object lodged between the blades.

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...

In this installation, an AC panel board was located at ground level which combined the AC circuits from string inverters on the roof. We wanted to avoid entering the top of the enclosure with conduits, so a trough was used so that the feeders could...

During O&M we often find combiner boxes and disconnect switches with water inside them, despite the box being NEMA 4 and fully gasketed, no top or side penetrations, and weather tight connectors properly installed.

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.

At this site, the intermodule wiring is zip-tied to the rails but the string homeruns are laying loose on the roof, which is poor workmanship. Over time the rough shingles will wear away on the insulation compromising its integrity and putting the...

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.

A roof drain clogged causing the water to rise in the surrounding area. This installation has poor wire management, as shown by a connector sitting loose on a ballast block. Once the water rose and got in the connector, it began to short out (burn...

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.

On our first operation and maintenance trip to this site, we discovered an old broken module stashed under a HVAC unit. This module was not secured, and would surely have become airborne during a hurricane or tropical storm. This module could have...

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...

Two things went wrong here. First, the vegetation was not maintained, allowing it to grow tall enough to shade the modules and cover the modules in lots of pollen. The second mistake is improper seeding. If the site has proper low-growing ground...

This installer gets full points for creativity, but fails miserably for inappropriate construction means and methods. These cables are not protected from physical damage, and they are not outdoor rated so the UV rays will deteriorate the cables...

NEMA 3R and 4 inverters and outdoor cabinets may be rated for outdoor use, but any scratches in the paint will expose the metal to rusting. Once the rust gets a foothold, it will quickly spread. In this case, the corrosion should be sanded, primed,...

PVC conduits are acceptable when used properly (lots of expansion joints). Metallic conduits (EMC, IMC, RGS) are more expensive, but should be in areas subject to physical contact with other items (such as riser up walls, in electrical rooms, etc)....