Preparing for the Hurricane Sandy: Generator sizing for water wells

Home Inspector with Northeast Water Wells Inc NH Lic# 59,60 and MA 762


Power Outage’s happen to everyone at some point, but how we deal with them is a different situation all together. If you have a well it is crucial to understand how a generator and well go together. Without understanding the proper sizing and techniques you could potentially ruin your wells pumping system.


As we get deeper into our winter months the common questions about how to use a generator with a submersible well pump will arise. The first and most important is safety; one of the most common mistakes of using a generator is not installing a Transfer Switch. Transfer switches are required by the National electric code and are used to isolate your generated power from the utility power. Use of the transfer switch prevents the power from back feeding into the utility power lines during power generation. You must also comply with all local, state, and national electric codes.

When sizing a generator for the well pump it is critical to ensure that the size is correct to avoid pre-mature pump failure. One of the frequent mistakes we see is undersized generators. Some generators have the ability to start the pump when they are new, although with a little wear and tear on them they no longer have the ability to do so. It is always recommended to research through the manufacturer to see what information is available to size a generator per your specific needs. If you are running a Well Pump only, a majority of pump manufacturers have charts for your reference. When it comes to sizing a whole house generator these numbers may be helpful in figuring the total equation as well. Most generators are sized in watts in order to get the total watts during run operation we need to multiply the volts times the amps to give you total running watts of the motor being used. Secondly the start up of the motor is critical in sizing the generator as well. To determine what the starting what are you need to multiply again the starting amps times the volts to determine watt the peak watts will be during start up. Start up may only take a split second to fire up although if it is not sufficient it could cause motor or generator failures. When in doubt your local well contractor is always a great source of information. Some things that you want to avoid while using a generator is poor connections, undersized wiring or long runs of wire, and running out of fuel during motor operation. Poor connections can cause excessive loss in voltage causing the pump to burn out. Another common issue we see is bad connection at the plug where wires have loosened up over time and cause the pump not to operate properly. With well pumps it is critical not to have the circuit breaker on until the generator is fully running and same for the shut down process as well. Once the breaker has been shut off then the generator can be shut down. If the pumps are subjected to improper start up, or shut down it can cause excessive wear to the thrust bearings, and cause pump failure.


Key things to remember during use of a generator are to fully understand the manufacturer’s instructions. Properly ground your generator per Mfg. instructions and local codes. In addition generators require proper ventilation for exhaust fumes and when refueling be sure to power-down then shut off the generator prior to adding fuel. Again when in doubt call your local Well Contractor for guidance.     


          Attached below is a generator sizing chart, to help you discover which generator you need for your well.

Comments (3)

Jeffrey DiMuria 321.223.6253 Waves Realty
Waves Realty - Melbourne, FL
Florida Space Coast Homes

they can truly be dangerous if you do not know what you are doing. Very informative post...thanks.

Oct 29, 2012 01:33 AM
Christine Smith
Buyers Brokers Only LLC - - Canton, MA
Exclusive Buyer Agent & Attorney, Canton, MA

Ashley...this is so important for homeowners who have wells and for those who are thinking of purchasing homes with wells!  Properly installed generators to keep those wells working are a must!

Oct 29, 2012 04:24 AM
Dave Halpern
Dave Halpern Real Estate Agent, Inc., Louisville, KY (502) 664-7827 - Louisville, KY
Louisville Short Sale Expert

Purchasing and installing an automatic standby backup home generator increases the value of the home. When reselling, buyers go ga-ga over homes with a generator, and the house will sell faster and for more than comparable homes without a generator.

Oct 01, 2017 08:57 AM