Factors to consider when selecting this jobsite workhorse

Enclosed generators offer a wealth of flexibility. In addition to the power-providing benefits of all generators, they can extend the range of power availability to remote areas of a jobsite, beyond the reasonable reach of power distribution cabling from a primary power source.

Compared to generators contained by site-built enclosures, enclosed generators usually offer superior sound attenuation, safety and ease of operation. Factory-enclosed generators are also more portable, and some can be towed with ease from one project to another.

The true value of enclosed generators is diminished if construction firms do not select the right unit for the job. In the case of an enclosed unit, that selection process goes well beyond kilovolt-ampere (kVA) rating, fuel type and other standard generator considerations. The characteristics of the enclosure itself are primary factors in achieving maximum ROI, regulatory compliance and jobsite productivity.

Enclosed generators now come in a wide range of sizes and power ratings, and they are available in diesel, bi-fuel and natural gas generator models. In some cases, selecting the right features and options can be pivotal to meeting jobsite requirements, especially if there is a requirement for specialized equipment.


Details as small as the panel hinges make a difference in the durability and service needs of an enclosed generator. Always specify stainless steel hardware for all hinges and latches, especially those that will be exposed to the elements.


For good overall durability and affordability, we recommend 11-gauge carbon steel construction for the enclosure. Also, require that any finishes be powder coated to inhibit deterioration. For salty environments, pre-painted aluminum may be a better choice, but it does not work well if sound attenuation is required. Carbon steel is suitable in salt-laden environments if it is rated as exceeding the 1000-hour salt spray test. Powder-coated aluminum is the most corrosion-resistant option, but also one of the most expensive. Stainless steel is generally rust free, but it is also expensive as an enclosure material and is not required for many environments.

Weather Resistance

Enclosures can be weather protective/resistant or weatherproof. Don't confuse these two descriptions. Also, do not allow a manufacturer to persuade you that a weather-resistant unit will suffice when it won't. If the generator must be able to withstand especially harsh conditions, including heavy, driving rain, hail, very high winds or extreme snow loads, we recommend you specify a NEMA 3R/IP67-rated weatherproof enclosure.

The definition of weatherproof varies from one manufacturer to another, so you may wish to compare metrics, such as roof load in pounds per square foot (PSF), rain penetration resistance in ounces of water PSF of inlet opening per hour and effective wind load in miles per hour (MPH). National or global standards may also provide some insight. Underwriters Laboratories (UL) has established helpful definitions for rain-proof and rain-tight.

External Power Distribution Panels

Enclosed generators offer a variety of built-in power distribution options. This one item can make or break your satisfaction with an otherwise suitable unit. For the construction industry, we recommend a minimum of three 50A, 125/250V twist-lock receptacles, two 20A, 125V ground-fault circuit interrupter (GFCI) duplex receptacles, convenient mechanical lugs and industry standard 400A CamLok-type receptacles. It is also beneficial to specify a brass termination between the generator and the distribution panel. Brass is stronger and more durable than copper but still sufficiently conductive.

It's important to note that GFCI breakers alone will not protect a generator from shutting down on overload. Without a circuit breaker, GFCIs on enclosed generators can cause the generator engine to shut down when they trip. The digital display may then show a message such as "overload," at which time the operator must redistribute the load and reset the generator. To avoid this hassle, look for enclosed generators that also offer an ABB UL-listed main-line circuit breaker (see External Switches and Displays).

Noise Dampening

In situations where sound is an issue due to local regulations, an amplitude (dBA) below 60 at seven meters (approximately 23 feet) may satisfy requirements, provided that the total noise emanation at the property line is not excessive due to other equipment. Even 70 dBA is quiet compared to many construction tools. If the generator will be running continuously (prime rather than standby power), it may have more impact on the sound restrictions imposed by a municipality or other regulatory entity.

Another issue with sound attenuation is the content of the insulation material itself. Some enclosed generators use insubstantial materials, such as foam, that can be damaged by liquids or physical contact. In our experience, rock-wool insulation (an excellent sound dampener) in resilient, long-wear panels that can be pressure washed provides an excellent combination of quality, durability and sound attenuation.

Make sure that the sound insulation material is also fire resistant and that it has been used, not only on the inside of the container itself, but also on the doors and ducting. Finally, don\'92t forget to consider auxiliary noise sources, such as the exhaust. Ask for a low-noise exhaust silencer as part of your package.

External Switches and Displays

Some of the switches and displays that companies take for granted on a traditional generator can be hidden out of easy reach on an enclosed generator. For maximum operability and safety, always look for:

  • Battery disconnect switch
  • External emergency stop switch
  • Digital control panel: These convenient panels help operators monitor the conditions of the generator. They should be back-lit with an easy-to-read LCD text display. They should include the following:
    • Manual and automatic start functions
    • Configurable engine alarms for high coolant temperature, low oil pressure, low coolant level, low fuel level, stop failure, low battery voltage, battery charging, alternator failure, over-speed, under-speed, start failure, emergency stop and unexpected shutdown; optimally, alternator alarms should be present.
    • Instrumentation, gauges and displays including voltmeter, hour meter, fuel, battery charger and voltage, oil pressure, water temperature, generator voltage and Hz, engine speed and other important operating parameters.
    • Engine parameter monitoring with configurable alarms and maintenance alerts
    • A tamper-proof hour counter

    This list covers the options most often requested by construction companies. Other beneficial features include pad-lockable door access, auxiliary bus bars (on the electrical panel) with mechanical lugs and the ability to configure the generato's displays to be viewed remotely from mobile device. A customer-service oriented manufacturer or dealer knows the right questions to ask to determine exactly what a company needs.