Generac Guardian 5873 17kW Standby Generator Steel Pre Packaged with 100 Amp 16 circuit ATS
Generac Power Systems

The Generac Guardian Model 5873 is a standby generator offered by Norwall Power Systems. It includes a 17-kilowatt generator and a pre-wired, 100 amp, Generac EZ Switch, which integrates the generator into your home's electrical system. Guardian series generators with automatic transfer switches start automatically and switch your home to generator power, protecting your home during a power outage, even if you are not home.

Fuel choices

Like all Guardian Series generators, the 5873 runs on LP or Natural gas. The availability of natural gas in urban areas makes it a common choice, but LP gas offers slightly more power. The generator produces 17 kilowatts with LP gas, while natural gas produces 16 kilowatts. Fuel cost also affects the choice between LP and natural gas. Operating at 50 percent load, the engine consumes about 1.6 gallons of LP gas, or 183 cubic feet of natural gas per hour. At full load, fuel use increases to 2.6 gallons per hour for LP gas, and 261 cubic feet per hour.


Generac's OHVI engine is the only engine in the industry designed specifically to run a generator. The 5873 incorporates a 32 horsepower, 992cc V-twin engine to turn the power generating unit at 3600 RPM. The pressurized lubrication system keeps it running for long periods without interruption. Although designed to run on both LP or natural gas, the engines are factory set for a natural gas installation, but are easily changed to LP gas by the installer.

Other engine features include reduced vibration, cooler operation, and low oil level sensing and shutdown.

Transfer Switch

The UL Rated EZ Switch is an automatic transfer switch that moves vital circuits from utility power onto generator power without homeowner intervention. The EZ switch mounts near the main distribution panel for simpler installation, homeowner convenience and access.

The transfer switch is pre-wired with 16 circuit breakers to simplify installation. Transfer switch wiring connects to the existing service panel through a 24-inch flexible conduit. Wiring connections for the generator are made through a 30-foot flexible conduit.

Nexus Controller

At the heart of all Guardian generators is the Nexus Controller. It starts and stops the generator, monitors and charges the battery, and alerts the homeowner to a failed or failing battery. Every week the controller starts the engine and runs it for a 12 minute exercise cycle.

The controller senses power outages and starts the generator after a programmable ten to thirty second delay which eliminates starting during a momentary interruption. After startup, the Smart Switch switches critical circuits to generator power. It continuously monitors the generator's voltage and AC frequency and makes adjustments as necessary for utility quality power. Once service is restored, the Smart Switch changes back to utility power. The controller then operates the generator in a cool-down cycle for an additional minute.

Another controller feature alerts the homeowner or installer to wiring faults and prevents damage to the electronic circuits. In the event of problems, the advanced wireless controller emits an audible alarm.

A Generac Advanced Wireless Monitor allows monitoring generator operation and controlling certain functions of the Nexus Controller indoors. The basic wireless monitor provides three LEDs that display the current generator status.

Generator Unit

The AC generator turned by the engine produces electricity. The combination of a revolving magnetic field inside a skewed-stator armature produces a smooth, clean alternating current that is free from spikes and noise. This design aids the starting of large motors with high inrush current requirements. Automatic voltage regulation keeps the output voltage steady for powering appliances and sensitive electronic equipment.

Appearance and Noise

The 5873 generator is housed in an unobtrusive steel cabinet with a Rhinocoat finish to provide long lasting weather protection and a clean appearance. The cabinet stands 29 inches tall, 48 inches wide and 25 inches deep and sits on composite mounting pad. The muffler is enclosed within the cabinet for safety and restricts noise levels to 66db or less.

100 Amp 16 Circuit Nema 1(Indoor Rated) Automatic Transfer Switch, Pre-Wired Conduits, Composite Mounting Pad, Flexible Fuel Line Connector, Pre-Wired External Connection Box.

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Generac Guardian 5873 17kW Standby Generator Steel Pre Packaged with 100 Amp 16 circuit ATS

Generac Power Systems Model #5873
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Country Living
Comment by Jim C. on 9th Nov 2014

My Mom and Dad are both in their 80's and live in the country. With the installation of the 6551 I can rest assured that they will never be without power, heat, ac and water. this is a great unit and worked perfectly upon startup. Should have installed this a lot sooner for them.

By the way, my son-in-law also has one for his home. I live in a motorhome or I would have one also.

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