Prefabricated Electrical Panels

With so much electricity being produced today at service stations and C-Stores, Bart Mercer explains one effective way to cut out the “static.”

The electrical and controls room, better known as the “Back Room,” in most retail service station/convenience stores has evolved dramatically in scope from an almost overlooked afterthought to one of the most critical paths in the successful startup and profitable operation of each facility.

The evolution of the Back Room is a direct result of the growth of the facility from a “two-bay service station” to the one-stop “omni-store” with extensive fueling, restaurant, grocery, car washing and banking product offerings. The combination of electrical, automation, communication, power quality and safety/regulatory requirements to support this expansive growth has transformed the previously overlooked Back Room into the central nervous system for the entire operation.

At the same time, the efficient utilization of square footage within these facilities for retail, storage and management has become of primary importance. For the successful operation of today’s convenience store, it is critically important to minimize the required space for Back Room equipment and to maximize the integration and reliability of all this additional electrical and electronic technology.

The concept of prefabricated electrical panels provides one of the solutions to this paradoxical problem: how to get more equipment in less space with better functionality. This concept provides preassembled cabinets shipped to the job site with all the electrical circuit breakers factory prewired to the critical fueling controls, lighting controls and power conditioning systems. Since these cabinets require less wall space than conventional electrical construction, more space is made available for the other Back Room equipment, such as tank monitoring, POS interface, telephone and security systems, which are not installed in the cabinets.

In addition to saving space and improving electrical system integration, prefabricated electrical panels have proven to provide many other construction and operational benefits.

Electrical expansionism
The growth of the electrical requirements for the retail service station/C-store is the driving force in the application and cost justification for prefabricated electrical panels. This growth has been exponential—increasing from a 200 amp, single-phase electrical service to 600, 800 and even 1,200 amp, three-phase electrical services. This is similar to the electrical capacity of an average home that grows to the size of a typical full service restaurant or medium-sized grocery store.

The advent of on-site food preparation has increased the requirements for refrigeration, cooking, warming, display and cleaning equipment. The floor space needed to provide this food preparation and other retail offerings requires additional interior lighting as well as increased capacity for heating, ventilation and air conditioning (HVAC).

Multi-Product Dispensers (MPDs) can now accept credit cards, cash and even remotely activated transmissions for gasoline, carwash, restaurant and in-store sales while providing advertising and entertainment with built-in video displays. MPDs can even provide attractive lighting displays and return environmentally hazardous vapors from the nozzle back into the tank. The technological advances of MPDs have been spectacular; but all this new technology and marketing sizzle requires more electrical “juice.”

Factors such as bigger building sites for the larger facilities, massive canopies to cover more dispensers and the additional marketing pressure to increase store visibility and customer security have created an expansionist trend in all forms of outside lighting. Impressive improvements in lighting efficiency technology have not offset the increased electrical load on the facility from building/pylon/canopy signage, fascia/neon strip lighting and canopy/site lighting.

When all these “kilowatt-hour loving loads” are added up, it is not difficult to understand the magnitude of the electrical expansion in retail service station/C-store facilities.

Microchips rule the world
There has been a similar expansion in the application and use of electronic systems stuffed with microprocessors (aka microchips) in the areas of communication, monitoring, automation and control systems to manage the facility and to increase many valuable customer service offerings.

The extensive use of sophisticated computer, POS, dispenser, telephone and satellite equipment which communicate with endless arrays of digital signals (0s and 1s) is now required to manage the transfer of information, authorization and monetary funds. Microchips rule this critical domain with absolute authority.

Automatic tank monitoring systems that use electronic sensors to measure incredibly small changes in product level, status and pressure use microchips to calculate, communicate and control the operation of the entire fueling system.

Even submersible pumps, the workhorse of product delivery, have become “intelligent” with electronic controllers that vary their own speed to maintain maximum allowable fueling capacity at the dispensers. The variable-speed controllers that operate this new breed of submersible pump must also be located in the Back Room with all the other equipment that already competes for wall space.

The previously mentioned increased use of outside lighting, cooking, heating and air conditioning equipment provides cost justification to use automatic control systems that operate these loads with great precision—and without human intervention. In these automatic controls, microchips monitor light and temperature sensor information to calculate the exact time to turn these large building loads “on” and “off.” This technology can save significant dollars on the rapidly escalating electric and natural gas bills while improving store operations.

Microchips talking to each other and working together provide the undisputed foundation for the successful operation of the business. Insuring this functional integration of different systems requires additional planning and investment.

System integration essential
The successful integration of all the electrical and electronic systems has become a major challenge because of the incredible diversity of products offered by manufacturers, each with unique installation and operating requirements.

Electrical, mechanical, fueling, computer and service contractors struggle to keep up with the application of these new products, along with all the related regulatory and code requirements. Unfortunately, these new technologies transcend the traditional “trade” lines of responsibility and no one on the job site is looking at the integration of these products from a system’s viewpoint.

Once upon a time, an owner’s primary concerns were involved in more of the “architectural” issues, such as building appearance, product merchandising, traffic flow and zoning requirements. Today, another primary mission of ownership must be to look at the “vision of system integration” in controlling the design and specifications for the entire facility, not just delegating these responsibilities to contractors who might not have the training or motivation to fully understand this vision.

Clearly designed, defined and documented interfacing of these systems helps everyone work together better and get the job done on time and on budget. However, even the best specifications and drawings will not produce the desired results without proper supervision and verification. This process can be very difficult and expensive to do on a consistent basis.

A critical interfacing problem in the retail service station/C-store application is meeting the electrical control, communication and code requirements involved in the wiring between dispensers, submersible pumps, emergency power shutdown, POS and tank monitoring systems. Most startup and operating problems occur in this area, which can erode earnings through delayed openings and unexpected shutdowns.

Prefabricated electrical panels provide a major benefit in this critical area because the electrical system integration is predesigned and wired into the system before it is shipped to the job site, leaving much less room for error. Much of the specified equipment and critical wiring is controlled in a factory environment where all the shop drawings, parts and quality assurance programs are already in place that do not exist on the typical job site.

Maximizing this integration of electrical and electronic systems requires a complete understanding of the interaction of all the equipment both inside and outside of the prefabricated electrical panels. Because this is an emerging technology, this level of knowledge is difficult to achieve and duplicate effectively with conventional electrical construction.

High tech electrical construction
With the typical cost of C-store construction averaging between $80 and $160 per square foot, efficient store planning and design is a key to maximizing the income producing space for retail, storage and management while minimizing the non-income producing spaces such as the Back Room.

Prefabricated electrical panels are designed to reduce the required wall space by 6 to 10 linear feet by the “stacking” and “packing” of components, thereby eliminating multiple enclosures, gutter boxes, conduits and connectors. Since electrical codes require a 3-foot clearance in front of electrical panels, this can reduce the floor space required for the Back Room by 18-30 square feet. This results in the minimum space possible for the electrical and control systems and provides the maximum integration.

This concept also “fast tracks” construction schedules by providing factory labor in parallel with field labor. While the jobsite is still performing site preparation, the prefabricated electrical panels are being built at the factory. The factory labor required for prefabrication is between 80 and 115 hours per system, depending on the size and design of the facility. With handling and installation of the prefabricated electrical panels requiring up to 10-15 hours of field labor, this provides a net reduction of 70 to 100 hours of field labor, which can put the construction schedule on a faster track.  

Prefabrication also reduces “startup problems” for dispensers, pumps, and lighting controls because the most difficult control wiring is done at the factory and pretested prior to shipping. This benefit is the most difficult to quantify in terms of labor or dollar savings, but has become one of the most valuable intangible factors.

The arrival of variable speed submersible pumps has provided an additional benefit to the prefabricated electrical panel concept as the pump controllers required for this technology can also be integrated and prewired into the cabinet.

With all the installed electrical and electronic equipment, these prefabricated electrical panels must, of course, be UL Listed as complete assemblies, and must also comply with the related National Electrical Codes.

Critical fueling requirements
For critical fueling requirements (such as emergency power shutdown, the avoidance of dispenser power cross-phasing and safety standards for dispenser maintenance), there are several different electrical methods that will achieve similar results. There are also many electrical methods to control the operation of outside lighting and to protect building equipment from electrical disturbances. Unfortunately, this diversity of electrical methods can create confusion and increase both service and maintenance costs.

Prefabricated electrical panels provide nationally consistent design, documentation, assembly and quality control to assure compliance with ownership and engineering requirements. Standardized designs for electrical distribution, fueling controls, lighting controls and power quality systems are easier to install and maintain for long-term operation.

As shown in Photos 1 and 2, the hinged cabinet door design of prefabricated electrical panels allows for superior access to all components and wiring for improved installation, serviceability and maintenance. This eliminates the need to troubleshoot the wiring problems in “gutter boxes” (see Photo 3).

Photo 1: Prefabricated electrical panel (800 amp service) with doors closed.			Photo 2: Prefabricated electrical panel (800 amp service) with doors open.

Electrical protection
There are many ways to protect the investment in a facility, including buying the right insurance, doing proper equipment maintenance and hiring good employees. The concept of power quality is one area of investment protection that is often overlooked and misunderstood. Like the homeowner who installs a security system after being robbed, most owners don’t address the issue of power quality until after a power surge cooks their microchips into a silicon soup.

Electronic systems, particularly when networked together, require stable power sources that are protected from surges, spikes, high frequency noise and improper grounding. Other electrical loads are more tolerant of power fluctuations, but still need protection from high energy disturbances such as lightning strikes and utility grid switchings. The quest for a unified power quality theory is still a “work in progress” with many conflicting concepts and philosophies.

The reason that power quality is so badly misunderstood is that different types of building equipment require different types of power protection to address different types of power problems. However, some manufacturers sell (and some people buy) a quick fix magic bullet that doesn’t address the proper application of protection at the right place.

There are several classifications of power quality equipment with a broad diversity of products available within each category. This includes surge protection, power conditioning, power filtering and uninterruptible power supplies (UPS).

Electrical protection is a controversial subject that is worthy of its own detailed debate in a future issue of PE&T. The subject is relevant to the concept of prefabricated electrical panels because some categories of power quality equipment can and should be designed and preinstalled into the cabinets.

Prefab history
The use of prefabricated electrical panels in convenience stores started in the early 1990s, when a single major oil company and a few large regional operators built larger C-stores in multiple locations. Several major oil companies moved toward this concept in the mid ‘90s.

With the successful application of this concept and the availability of documented performance and specifications, this concept has become a viable option in the dealer/jobber C-store market.

As with all new technologies, there was and still is resistance to this conception, primarily from electrical contractors—some of whom view prefabri- cated electrical panels as a competitive threat. However, after installing these systems, most electrical contractors realize that they also benefit from this concept through simplified construction and reduced startup problems.

Now, some of the most ardent supporters of this concept are electrical contractors; some of whom have even promoted it at other projects on which they work.

The “catch”
Prefabricated electrical panels offer many strong benefits and solutions to several problems. However, without a corporate commitment to provide the necessary design and construction documentation, both the installation and operational benefits will be diminished. This concept is not for everyone.

Without proper design conversion from conventional electrical methods, problems can occur such as:

• misalignment and improper length of electrical conduit stub ups;
• inadequate door clearances; and
• w incorrect field wiring to remote peripheral equipment (i.e., tank monitors, dispensers, light sensors and emergency shutdown switches).

Proper documentation is also critical so that the bidding contractors fully understand what is included with the prefabricated electrical package and what is required for field wiring so that the duplication of labor and material is avoided in preparing their bid. This, by far, is the biggest challenge in the cost justification of this concept.

The cost
In fact, the emergence of this concept has created the need for engineering firms that provide technical services to convert existing prototype drawings to include the prefabricated electrical panels into the building’s electrical and mechanical design.

Because the prefabricated electrical panel, by design, is a lump sum cost for a broad spectrum of material, labor and support, the panel sometimes becomes a target for construction managers, accountants and purchasing agents who must reduce costs.

There will always be a temptation to return to the old “Back Room” ways, where these same costs are buried in the overall building contract and deflected to future operating and maintenance costs.

However, for companies that look at true long-term ownership costs in both construction and operations, returning to the conventional “Back Room” will never again be an option.

Installing Electrical Prefab Panels
Prefabricated electrical panels have special installation requirements. Underground electrical conduits that are going into the cabinets must be stubbed up within a predetermined “footprint” of the cabinet sections. These conduits must be kept as short as possible to minimize space requirements and to avoid interference with internal components.

“Seal off” type electrical fittings are installed on the dispenser and pump conduits with standard fittings installed on all other conduits. Since the traditional gutter box is eliminated, bonding bushings and ground wiring must be installed on all the fittings to provide the grounding of all conduits that is required by the National Electrical Code.

After the concrete slab is poured, the prefabricated electrical panels, which have open frame bottoms with flanges, are set in place over the conduits and bolted to the back wall. Other electrical conduits that don’t come underground are simply installed directly by cutting holes in the top or side of the cabinets. With all the conduits in place, the entire cabinet becomes an oversized junction box for all internal wiring.

With conventional electrical construction, wiring has to be routed through tightly packed gutter boxes, nipple connectors, panel boxes and control junction boxes. With the cabinet doors of the prefabricated electrical panels open, all the wiring and termination points are readily accessible for easy routing and installation. This hinged cabinet door feature also provides the same benefit for service and maintenance.

New construction and major remodels are good candidates for prefabricated electrical panels. Existing sites with adequate electrical breakers and panel boards are not good applications of this concept.

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