A Timely Topic – Using a Generator with a Franklin Sub

As a result of the recent weather events on the east coast, Franklin Electric’s Water Systems Technical Hotline has been receiving a high number of calls concerning the use of generators with submersible installations. In order to provide an easy reference for all, it makes sense to review generator sizing here in Franklin AID.

Note: The use of generators must follow all local, state, and national electrical codes. ALWAYS consult these codes before installing a generator. In addition, make sure the generator is properly ventilated and that you are familiar with its operating instructions before putting it into use.

Guidelines specific to using an engine driven generator with a Franklin submersible motor can be found on page 5 of the Franklin Electric AIM (Application, Installation, and Maintenance) Manual.

To determine proper sizing, refer to Table 5 on page 5 of the AIM Manual. (Click the illustration above for a close-up view.)Note that the numbers in the sizing chart apply to both 3-wire and 3-phase motors. If it’s a 2-wire installation, the minimum generator sizing is 50% higher than listed in the chart. This is because of the higher starting current required for 2-wire motors.

Also note that the sizing chart only applies to one submersible motor. If other devices are being powered, they must be identified along with their power consumption. Even though some of these items may not run continuously, they still need to be taken into account, per the generator manufacturer’s recommendations.

The frequency of the voltage delivered by the generator will be a function of the engine’s RPM. Motor speed varies with the frequency of the output voltage, and since pump affinity laws relate power to performance, generator sizing can have significant impact on pump output. For example, if the generator is putting out a voltage at a frequency that is below 60 hertz, the pump will not meet its performance curve. Likewise, if the frequency is above 60 hertz, it may overwork the motor and trip its overloads. The generator manufacturer’s instructions will contain guidance on how to adjust the generator’s frequency. Of course, you’ll also need a voltmeter that measures frequency. Most of today’s digital voltmeters contain this function.

The thrust bearing in a submersible motor requires a minimum speed of 30 hertz (about 1800 RPM), so it is important to start the generator before starting the motor. Likewise, it is equally important to stop the motor before the generator is shut down. Failure to do so may result in damage to the motor’s thrust bearing during start-up and coast down. The installation of a simple transfer switch will allow the motor to be turned on and off independently of the generator. (Note: circuit breakers should NOT be used for this function.)

More critically, a transfer switch also functions as a safety device to isolate the utility electrical supply from the generator. Without a transfer switch, the generator can back feed into the utility lines and, in a worst case scenario, cause serious injury or death. Unfortunately, the transfer switch is one of the more commonly overlooked safety devices required by the National Electrical Code (NEC).

Code also requires that the generator be properly grounded in order to protect against electrical shock in the event of a fault. Like all electrical conductors, the ground wire must be correctly sized for the load it is designed to carry.

Hopefully, you won’t find yourself in a no-power situation that necessitates using an engine-driven generator. In the event that you do, taking appropriate precautions and following this protocol will help make sure you can get your Franklin sub back online.

Why Motors Fail: Part 1

When you think of Franklin Electric, we hope that quality and durability come to mind. That is what we strive for everyday, and after decades of service to the water industry, we are proud to continue providing quality products and reliable support. However, even in the most reliable applications problems can occur, causing a motor to prematurely fail. In the next two issues of the Franklin AID, we’ll examine the most common reasons for application motor failures.

Motor failures come in three basic types: electrical, mechanical and mechanical that progresses into electrical. We’ll first focus on electrical motor failures and next issue will look into mechanical failures. Both will share tips for avoiding application-related problems and getting the longest life out of your pumping installation.

About eighty percent (80%) of electrical motor failures are a result of winding damage in the motor stator, due to either overheating or voltage issues. Electrical motors take electrical energy and convert it into mechanical energy, producing heat as a by-product. In submersible motors, that heat is removed by the flow of the water past the motor. Overheating is always either caused by a lack of cooling flow, or the generation of more heat than can be displaced. Continue reading

Assembly of 4-Inch Motors and Pumps

As a water systems professional, you probably assemble large motors and pumps in the field on a regular basis. However, there are also occasions when you may need to assemble smaller 4-Inch pumps to motors, either in the field or back in the shop. For example, the assembled unit you took to the job site may not turn out to be the one you actually need. You might have planned on installing a 115 V unit, but you discover at the job site that you actually need a 230 V motor instead. If you have that 230 V motor on the truck, you can simply switch motors. In other cases, you may not have the right GPM pump rating and motor combination, and you have to “mix and match”. Finally, for a variety of reasons, some contractors simply prefer to purchase their pumps and motors separately, and perform the assembly themselves.
In this issue of Franklin AID, we’ll review the proper procedure for assembling a 4-Inch pump and motor in the field. The steps are straightforward, but merit a quick review.
Continue reading

Overload Protection for 3-Phase Motors

Several conditions can cause a motor to become overloaded. Examples include a bound pump, or a high or low voltage condition. When a motor becomes overloaded, the current (amps) increase, and can reach levels damaging to the motor. Therefore, a motor must be protected from an overload condition, and this is the job of the overload protector, sometimes just called the “overload”.

In a recent edition of the Franklin AID, we discussed overload protection in Franklin Electric single-phase motors. These motors contain “built-in” overload protection, either in the motor itself or in the Franklin Control Box, depending on the horsepower rating. In this issue, we will discuss 3-phase motor protection. Continue reading