Sizing a Generator Transfer Switch

The Importance of Sizing Generator Transfer Switches
Electrical Question: If I have a 50 amp inlet can Reliance Model 31410B 10 Circuit Transfer Switch, is it rated for 12,500 watts? My electrician installed a Reliance Pro\Tran Model 31410B 10 Circuit Transfer Switch that says its a 30AMP, but he says it is the same as the 50AMP 51410B. Is this true? Will I still be able to pull in 12,500 watts? The inlet does plug into my 50AMP out on my generator but I don’t have a watt meter to verify

This electrical question came from: Steven, a Homeowner from Washington Township, Michigan.

Dave’s Reply:
Thanks for your electrical question Steven.

Sizing Generator Transfer Switches

Steven, lets do some basic math here and you will see for yourself what the rating is:

The Steps for Sizing a Generator Transfer Switch

To calculate watts, the formula is amps times volts.

• Examples, assuming your generator has a 240 volt output:
• 30 amps times 240 volts = 7,200 watts
• 50 amps times 240 volts = 12,000 watts

Steve, I will just say that you better have your  electrician explain his calculations to you, then compare the results to the rating of the equipment, along with the rating and size of all the electrical components to make sure your system is sized properly.

• It is essential to properly size the home generator, the transfer switch and electrical wiring and electrical components, and this size must be determined according to the anticipated electrical loads that will be placed on generator power.
• Identifying and understanding the types of loads is extremely important as well. For example an average generator should not be used for a typical well pump.

More about Generators and Transfer Switches:

Home Electric Generators

• Home Electric Generators

• This series covers a wide variety of topics all about home generators including sizing, selecting, connecting and safely operating this all important addition to your home.

• Generator Section
• The Importance of a Generator Transfer Switch
• Generator Resources
• Generator Questions and Answers

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