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Generac Guardian 5875 20kW Standby Generator (Aluminum) Pre Packaged 200 Amp Service Rated ATS

Generac Power Systems Generac Power Systems
Model#: 5875
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Maintenance Kits, Replacement Parts & Accessories

Generac Power Systems 6212 Details and Specifications

The Generac Guardian Series of standby generators are designed to start and operate automatically during a power outage. The Generac Model 5875 package is a popular standby generator with a Nexus Controller sold by Norwall Power Systems and includes a 20-kilowatt generator packaged with an 200 amp, service-entrance-rated automatic transfer switch.

Fuel choices

All Guardian generators operate on either natural gas or on LP gas. Availability and cost are the main factors in choosing between the two fuels, but the fuel choice also affects the power output of the generator. The 5875 can produce a continuous 20 kilowatts of power using LP gas, but that is reduced to 18 kilowatts for natural gas. Fuel consumption at fifty percent load runs about 1.9 gallons per hour for LP gas and 2.9 gallons per hour at full load. Natural gas use is 206 cubic feet per hour at half load, and 294 cubic feet per hour at full load.


The engine is Generac's own overhead valve industrial engine; the only engine designed specifically for use in a generator. The design of the V-twin, 999 cc engine allows for extended operation with an extended maintenance cycle twice that of most generators. It runs cooler and smoother with less vibration and easily switches from natural gas to LP gas in the field.

The engine senses low oil levels and shuts itself down to prevent damage. Pressurized lubrication helps keep the engine operating smoothly and for extended periods without interruption.

Transfer Switch

The Generac Nexus Smart Switch is a UL rated, automated transfer switch that handles the changeover from utility power to the standby generator in the event of a power outage and incorporates load management for high demand appliances. The switch is normally mounted close to the existing service panel for ease of access, installation and convenience.

The Smart Switch incorporates load management for high demand appliances through a load-shedding controller and manages one or two air conditioners without additional equipment, and up to four additional high demand appliances with the addition of Demand Load Management modules.

Nexus Controller

The Nexus Controller is an integral component of all Guardian generators and manages generator functions. Once a week it starts the 5875 generator and exercises it for 12 minutes. When the generator is not in use, the controller monitors and charges the battery to ensure it is ready when needed and alerts the owner to replace the battery when it will no longer hold a charge.

When a power outage occurs, the controller senses the outage and waits to ensure it was not a momentary interruption, then starts the generator after ten to thirty seconds (programmable). During operation, it monitors generator voltage continuously and adjusts it for utility quality power, and also controls the frequency to keep it at a steady 60 hertz. When utility power is restored, the controller instructs the transfer switch to change back to utility power, but continues to operate the generator in a cool-down mode for up to one minute before shutting it down.

The controller also senses incorrect/improper wiring to alert the user and prevent damage to the system. If the any part of the system shuts down, it can notify the homeowner through a general alarm displayed on the generator control panel. The optional advanced wireless remote controller sounds an audible alarm if a malfunction is detected.

Generator Unit

The alternator or generating unit is the heart of the system that produces electricity. It utilizes an efficient revolving magnetic field and a stationary armature with skewed stators that keep the current output smooth, clean, and free of spikes and noise. The unit employs automatic voltage regulation for continuous, unvarying power and also helps to provide for the momentary high inrush currents required by electric motors during startup.

Appearance and Noise

The overall appearance is clean and unobtrusive, with a smooth, protective case. The entire unit stands 28 inches tall, 47 inches wide and 25 inches deep. The aluminum cabinet resists rust and is covered by epoxy paint for a long lasting finish. The engine's muffler is located within the cabinet to guard against burns and injury and keeps the generator's noise level to 66db or lower. The 5875 package includes the fascia and trim kit normally sold as an accessory.

20kw Generac Generator 5875 Includes:

200 Amp Service Rated Nexus Smart Switch with Digital Load Management Technology Nema 3R Rated #RTSD200A3, Flexible Fuel Line Connector, Composite Mounting Pad, Base Fascia
USA Engineered & Built

Generac $50/$50 Referral Rebate, Click Here

Product Specifications

Model Number 5875
Manufacturer Generac Power Systems
Made In USA Yes
Rated Watts 20 kW
Rated Amps 83LP/75NG
Voltage 120/240V Single Phase
A/C Ton Rating 5 Tons
Enclosure Aluminum
UL Listed Yes
Decibel Rating 66 db(A)
Starting System Electric/Automatic
Low Oil Alert Yes
Idle Control No
Hour Meter Yes
Battery Requirement Requires 12Volt, Group26R-525CCA
Mounting Pad Composite (Included)
Product Weight 451 lbs.
Dimensions (Inches) 48L x 25W x 29H
Engine Brand Generac
Engine Size 36 HP/999 cc
Engine RPM 3600 RPM
Cast Iron Sleeve Yes
Cooling System Air Cooled
Alternator Type Brushed
Frequency 60 Hz
Auto Voltage Regulation Yes
Fuel Type LP/NG
NG Power Capacity 18kW
LP Power Capacity 20kW
NG Consumption @ Full Load 294 cu.ft/hr
NG Consumption @ 1/2 Load 206 cu.ft/hr
LP Consumption @ Full Load 2.90 gal/hr
LP Consumption @ 1/2 Load 1.89 gal/hr
Transfer Switch
Transfer Switch Model RTSD200A3, Nema 3R, Outdoor
Transfer Switch Amps 200 Amps
Transfer Switch Circuits Whole Panel, Service Entrance Rated, Nema 3R, Outdoor Rated
ATS Poles 2 Poles
Warranty Information
Consumer Warranty 3 Years Limited
Commercial Warranty 3 Years Limited
Shipping Weight 572 lbs
Shipping Dimensions 45H x 50W x 27D
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Product Reviews

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  1. Flawless

    Posted by GEM on 14th Aug 2012

    I bought this last November and it has been flawless from day 1

  2. Excellent Choice

    Posted by Charles A on 10th Aug 2012

    Generator was ordered on line and was delivered in five days at my door.
    The truck had a lift gate and the unit was delivered exactly where I wanted it.
    After the wiring was completed and everything checked out, the power company shut the power within one hour of completion to do maintenance.
    The generator started automatically and switched to the generator power and ran for about two hours.Since that time we have had a few power interruptions due to the utility company changing underground cable in our area. The Generac 5875 has performed flawlessly. This was a great investment.

  3. Only 1 small issue.

    Posted by Randy LaRowe on 10th Jul 2012

    So far, the generator is everything it is advertised to be.
    Excellent fit and finish.
    There are only (2) suggestions for improvement.
    1. Make the "customer connections" easier to access.
    As it is built now, I had to disassemble the generator output supply breaker from the housing, to connect my leads to the ATS. I would like to see another "panel" built into the side or back of the unit that would make the connections simple and much easier to work with.
    2. Add 1 more conduit opening for the DC wiring. I work in the controls field, and we are always directed to keep DC voltage wiring separated from any AC conductors due to EMF. This may not be an issue with this type of equipment.

  4. Great product

    Posted by Joseph triano on 18th Jun 2012

    As an electrical contractor i install a lot of generators we find the Generac to be the most user friendly and easiest to install, i have yet to encounter a problem with these Generac products.
    Norwall has been excellent to deal with, the website is great and the customer service outstanding i buy all my generator product using Norwall.

  5. Norwall Customer Service is Awesome

    Posted by Rodger S on 16th May 2012

    Had contact both voice and email with Rebecca, Jeana, and Karen during the purchase and shipping process. The personal attention they gave to my order was nothing short of Outstanding. All of my questions were answered in a timely manner, and they followed up with email confirmation. Your wasting time looking elsewhere for generators or maintenace equipment. I would highly recommend Norwall to all of my relatives and friends.

  6. Happy Customer

    Posted by Doug A on 11th Apr 2012

    great product, great price. Came quickly. Delivery company did not want to drive into my neighborhood so electrician met nearby, no problems.


    Posted by Kenneth S on 6th Apr 2012

    Ordered by E-mail without any hitches or confusion on 3/29/12. Delivered on 4/3/12 in perfect condition, not even a mark on the crate.
    "Hats Off" & " Cudos" to Norwall and UPS Freight. (Driver was very helpful at curbside drop & inspection for damage) By the way the generator is a "5875 20Kw STANDBY"..

    Would not hesitate to use Norwall in the future and anticipate a flawless installation and start up. Almost anxious for the next power outage !!!

    Go ahead, "Take the plunge" I am sure your experience will be the same as mine, "OUTSTANDING" !!!!

  8. Great experience and generator

    Posted by Robert V on 29th Mar 2012

    I ordered and received a 5875 in 2011.

    The generator was delivered on time. The lift gate service worked out extremely well, and the driver even had a pallet jack to move the generator exactly where I wanted it in our garage (I gave him a tip for doing this).

    The unit was installed in September and has worked great with one exception. I experienced a control panel issue (a false under voltage alarm) about after having the unit for 5 months. Generac paid an authorized service person to replace the controller with a new controller with updated software under warranty. No cost to me whatsoever. I was impressed.

    While we haven't experienced a true outage yet, but one morning we had lots of power fluctuations from the power company during some bad weather. I decided it was better to run the generator than to continue with the utility fluctuations, so I turned off utility power via the main breaker in the service rated transfer switch. The generator started right up and worked perfectly.

    Every 2 months, I also simulate a power outage (by turning off utility power as described above) to test the generator (under load) and transfer switch (to make sure it transfers properly) for my own piece of mind.

  9. This is the one

    Posted by Richard in Arkansas on 12th Mar 2012

    I searched and made all kinds of comparable s and finally purchased this
    unit and glad I did. It just keeps on going and going. Maintenance is easy
    and low noise. You will have power to spare for what ever you want to run.

  10. Worth every penny!

    Posted by Dave Harmon on 25th Feb 2012

    Owned for 2 years. Great peace of mind. I never have to worry about power going off when I am at work at the firehouse and my wife and kids are home. 10 seconds after power failure, whole house is running as usual. Runs everything we need. We have used multiple days at a time on several occasions. Best Price and easy shipping.

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