Cummins 20kW NG/LP Standby Generator Package with 200 Amp Automatic SE Rated Transfer Switch RS20 W250
Cummins Power Generation

Norwall Power Systems offers the Cummins Power Generation RS20A standby generator package that includes a 200 amp, service entrance rated automatic transfer switch. This generator runs on either natural gas or LP gas, and supplies up to 20 kilowatts of power continuously to keep the lights on and essential appliances operating during a power outage.

The RS20A is U.S. EPA and CARB Emissions compliant for use in all 50 states. Unlike other residential standby generators, the RS20A and 200 amp ATS package comes with an in-home display for easy setup and monitoring from inside your home. The package also includes two 50-foot-long wiring harnesses, one for the low voltage wiring between the generator and transfer switch, and the other from the generator to the in-home display panel.

Fuel Choices

The RS20A offers a choice between natural gas and LP gas. LP gas allows the generator to run at full power and supply 20 kilowatts of power. Under full load, it consumes about three gallons of LP gas per hour, and 1.5 gallons of LP gas at half load. When powered by natural gas, the generator is capable of 18 kilowatts. Fuel consumption runs at 240 cubic feet per hour at full load, and 135 cubic feet per hour at half load.

Fuel consumption is variable and is directly related to the amount of power being used at any moment. Fuel usage will vary over time as the amount of power being used changes.


The engine in the RS20A was designed by Cummins. It is an air-cooled, 993cc, overhead valve v-twin that operates at a steady 3600 RPM. The engine runs on LP gas or natural gas and is easily converted during installation for either fuel. This motor had a fully pressurized lubrication system similar to those used in automobiles and includes an oil filter and oil cooler. An electronic governor keeps the engine turning at a constant speed to ensure the generator outputs the required frequency. The maintenance schedule calls for oil and oil filter changes every year or after 100 hours of operation, and an air filter change after 400 hours.

The 200 amp RSS200-6869 automatic transfer switch supplied in this package is service entrance rated, which means it is suitable for installation between the distribution panel and the electric meter. This allows the transfer switch to select the source of electric power from the utility or from the generator as needed and connect it to the distribution panel. When the utility power is interrupted, the generator starts and the transfer switch selects the generator as the power source. When utility power is restored, the transfer switch reconnects the distribution panel to the utility supply and the generator runs at no load to cool, then shuts down automatically.

This controller works with the transfer switch to incorporate advanced load shedding for exceptional management of high-demand loads.

Controller and In-Home Display

The controller on the RS20A incorporates Cummins designed electronics controls for generator setup and operation, and includes features that protect the generator and provide safe operation. On signals from the automatic transfer switch, the controller starts or stops the generator as needed, and also runs the weekly exercise program, which makes generator operation fully automatic.

The in-home display is powered through the wiring harness and does not require a battery. It indicates maintenance requirements, tracks and displays up to 30 faults and the last 30 events. It also allows the operator to control and configure the automatic transfer switch, and provides power usage statistics that help the homeowner manage generator power.

With Internet and Email connectivity, the controller can send you an email if service or maintenance is required, and allows you to monitor the generator status from an Internet connection.

Appearance and Noise

The generator is 53 inches long, 43 inches wide and 35 inches high. It sits on a polypropylene base suitable for either concrete pad or gravel bed installation. It has a heavy duty aluminum enclosure covered with powder coat architectural paint and a UL listed, polypropylene cover. Maintenance points are reachable without tools. Check the oil by lifting the hood and pulling the dipstick.

The RS20A is one of the quietest 20kW generators on the market and operates at 62dB, quieter than most central air conditioning units.


Includes (2) 50 Ft Installation Harnesses:

p/n A029U302 Easy plug-n-play harness connects low voltage wiring between generator and transfer switch.

p/n A029U308 Easy plug-n-play connection from remote display to RS air-cooled generators. Color coded for easy installation.

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.

Read More Customer Reviews