The reliability of emergency power systems has been significantly enhanced by NEC-required temporary generator docking stations, which are used to facilitate the connection of a portable generator when the permanent generator is unavailable. These docking stations provide a simple method to maintain emergency power continuity; however, when specified in a “dual-purpose” arrangement, they go well beyond their original intent and greatly improve overall system functionality. This article presents a simple, low-cost recommendation that delivers substantial long-term value for the owner.
The Role of Generator Docking Stations in Emergency Power
Generator docking stations serve a simple goal: provide a safe, Code-compliant way to connect a portable generator to accept building loads during utility outages, or when permanent generators are offline for service. Traditional single-purpose designs focus solely on generator connections, and overlook the equally important need for load bank testing.
Load banks are indispensable for verifying generator performance under simulated loads, ensuring compliance with standards like NFPA 110. Without integrated provisions, connecting a load bank typically requires improvised methods, such as running cables through buildings and using temporary means of connection—practices that introduce safety risks and considerable downtime. Considering that every generator that undergoes service should be tested prior to being brought back online, having provisions for easy testing should be a natural design approach.
Benefits of Dual-Purpose Design
Specifying generator docking stations as “dual-purpose”, incorporating provisions for temporary generator and also for load bank connection, not only enhances system reliability but also streamlines maintenance and testing procedures. Opting for a dual-purpose docking station design means that the docking station now includes dedicated load bank terminals, allowing quick, outdoor connection of a portable load bank to make testing efficient and much less disruptive.
This is how the owner benefits:
- Enhanced Testing Efficiency: Dual-purpose stations enable load bank connection directly at the docking point, eliminating the need to access indoor generator rooms. This reduces setup time and minimizes operational interruptions, allowing facilities to maintain power continuity during tests. For high-rise properties, where permanent generators may be on a higher level, a curbside connection for a load bank is especially beneficial.
- Improved Safety and Compliance: Connections between the docking station and the building’s emergency power system are permanent and pre-established. Dual-purpose docking station designs incorporate protective features, such as interlocks to ensure that a load bank is disconnected in the event of a power outage.
- Long-Term Reliability: Regular load bank testing helps identify issues early and can help avoid unexpected failures. With dual-purpose provisions on a docking station, generator testing can become a routine task rather than a logistical challenge that may drive the owner to skip regular testing.
Pre-established testing procedures, combined with safe and efficient operation, translate to significant operational savings over time, and a higher level of confidence in the emergency power system.
Weighing the Costs: Minor Investment, Major Payoff
So, what is the additional investment when choosing a dual-purpose configuration? First, the designer should consider the costs associated with running the generator power conductors to the docking station. Second, consider the incremental equipment cost for the docking station itself, which is relatively minor—often just 10-20% more than a single-purpose version. The increase is due to additional breakers, buss work, and CamLok connectors. In my opinion, the equipment added costs are dwarfed by the future costs of not having these features, not to mention the non-monetary advantages that I discuss here.
For instance, skipping load bank provisions on a docking station may save a few thousand dollars upfront, but could lead to tens of thousands in future modifications or downtime. Set up time alone for a load bank test with no easy connection to the emergency generator, can be a multi-day effort. The extra labor costs for one such test event can be multiples of the initial investment required for a dual-purpose docking station.
What are the design options?
In any design involving a dual-purpose docking station, the designer should understand that the docking station must have a direct connection path to the permanent generator output. In other words, when the load bank is connected to the docking station, the docking station must have a connection to the permanent generator. Given this basic requirement, dual-purpose docking stations may be specified in a number of different configurations.
- Docking station with Kirk-Key interlock – this basic design allows a load bank to be connected to the permanent generator’s output (whether directly to the generator’s output breaker or to an emergency switchboard). Connection of a portable generator (through the CamLok access panel) requires that the permanent generator output breaker be opened (via Kirk Key interlock).
- MTS/Docking Station – this design uses an integral manual transfer switch to prevent simultaneous connection of permanent and portable generator power sources. The load bank has a direct connection to the permanent generator output, and the portable generator is connected to the building loads via the MTS.
- Single-Breaker, Dual-Breaker or 3-Way Switch – these utilize one or more circuit breakers (or switches) to perform interlock and protective functions. These can provide the most functionality and ease of operation.
Which is best for any given project? Like most things, pros and cons exist for each configuration, and should be reviewed on a case-by-case basis. I often speak to electrical design firms and do a deep dive into each of these designs to point out technical features and real-world scenarios that will impact the owner’s experience (issues that are not always obvious on paper).
Pro Tip: Look for a dual-purpose arrangement that permits load bank testing of the permanent generator, while the portable generator is connected and serving critical loads. This arrangement should allow physical connection of all permanent and temporary power sources, without having to take any offline, and should provide quick means to safely switch between these alternate power sources. This “switching” should be performed at a single location (ideally right at the docking station). Here is one example.
Why “Dual-Purpose” is a No-Brainer for Emergency Power Design
Generator docking stations which are not specified with dual-purpose functionality miss out on the serviceability needs that will surely come up for the facility’s owner. If we set out to design an emergency power system that is reliable, and that is able to retain that reliability over the long term, generator testing cannot be optional. If the ability to perform generator testing is part of the owner’s design criteria (as it should be), a dual-purpose docking station is a natural design choice. The efficiency gains, safety improvements, and compliance assurances will be of substantial value to the facility’s owner for years to come.
For expert assistance in the design and selection of generator docking stations, consider partnering with On-Site Power Advisor. With 30+ years of experience in the industry, On-Site Power Advisor offers tailored solutions to meet your project’s needs.