Transfer Switch For Your Portable Generator: Buyer’s Guide

Last Updated on by Matt

generator transfer switch

If you are wanting to add a backup power source to your house in the form of a portable generator, there are a few things you will need to make sure you know before making the jump.

The most important being a transfer switch.

Not only are there safety precautions needing to be followed when installing a transfer switch, there are also important guidelines to follow for code regulations for your home.

In this guide I will be discussing what a transfer switch is, the types of transfer switches, which switch is best for your home, and how to use it to transfer power from your generator to your home.

By the end of this guide, you will be about to make an educated, informed decision on the proper transfer switch for your application and the needed steps to get it properly installed.

What is a Transfer switch?

3d drawing showing the location of an electrical transfer switch
Image credits: This Old House

A transfer switch is an electrical switch that transfers electrical power between two sources.

In our case, an automatic transfer switch (ATS) is installed between your home and the generator near the electrical panel.

This transfer switch allows you to have your portable generator provide power to the circuits you want to power in the event of a power outage.

With a transfer switch installed, you eliminate the need for running extension cords to each individual appliance which makes for a safe, up to code installation.

Do I need a transfer switch?

While a transfer switch is technically not needed, we are going to look at why we highly suggest having one installed when connecting a portable generator to any appliance in your home

  • It is required by the National Electric Code

When using a portable generator to power appliances in your home, it is required by the National Electric Code (NEC 700.5 and 701.5) to have a properly installed transfer switch.

This is especially important if you plan to sell your home in the future as this will cause a code violation if not installed properly.

  • It is the easiest way to power your home during a power outage

Since most of your important electrical appliance like air conditioning units, furnaces, and water heaters are hard wired, they cannot be connected to a generator by an extension cord.

Also, having to find, untangle, and run extension cords during a blackout should be the last thing you need to worry about.

A transfer switch allows for the power to instantly switch over to the portable generator during a power outage for a quick, easy, and reliable alternative power source.

  • It is the safest way to connect a portable generator to your home

Using extension cords can cause back feed from the power traveling back down the utility line.

This increases the risk of fire or electrocution which could result in serious injury or death.

What To Look For In A Transfer Switch?

With the vast selection of transfer switches available, there are going to be a few things you want to look at when selecting the best one for you.

I have made this easy with a quick guide on what to look for.

Type

There are two main type manual and automatic. We will dive into the differences below.

Comprehensive Kits

To ensure that you are getting everything you need to make an installation quick and easy with the correct parts, having an all in one kit is essential.

Most switches are sold as a kit, however, you want to double check to prevent having to piece things together.

Wattage Rating

When looking for a transfer switch, one of the most important requirements will be the amount of running watts it will be able to support.

It is crucial to determine which circuits you want to power through your switch and calculate the amount of watts it will take to run them.

UL/CUL Certifications

Most brand name switch kits will have these certifications, but it is always a good idea to double check to ensure they are up to code specifications.

Warranty

As with any purchase, you will want to check to see how well the company stands behind their products.

With anything that will be handling a large electrical load, it is nice to have that peace of mind that you are warrantied.

Types Of Transfer Switches

automatic vs manual transfer switch comparison

There is plenty to learn about transfer switches such as open-transition, closed-transition, and delayed transition switches.

These are very important in the business and office settings, but for the sake of this article, we are going to be focusing on home use only.

For home applications, there are two types that we will look at, the manual and the automatic transfer switch.

Each has its advantages and depending on your budget and application, you can select which is best to fit your needs.

So let’s take a look at each and determine what would be best for your application.

Manual Transfer Switches

A manual transfer switch allows you to manually switch the power source from grid to generator with the flip of a switch.

These switches are much less expensive than automatic transfer switches but will require you to access your switch during the event of a power outage.

They also allow you to manually manage the amount of load on your generator to prevent overloads.

Pros

Pros
  • Inexpensive – Manual switches are less expensive than their ATS counterparts.
  • Easy To Control Loads – With switches on each circuit, you can control the load that your generator is under to prevent overloading.
  • Easier To Setup – With less moving parts and no programming needed, a manual switch is much easier to install

Cons

Cons
    • Requires Manual Switch Flipping – In the event of a blackout, you will be required to manually flip the switch to allow your generator to power your home.

Automatic Transfer Switches

An automatic transfer switch allows you to automatically switch the power source from grid to generator as soon as you lose power.

These switches can be programmable to automatically power the highest priority circuits during a black out.

With convenience comes cost, and these automatic transfer switches are no exception. With more features & higher maximum watt ratings, automatic transfer switches are generally priced higher than manual transfer switches.


Pros

Pros

  • Easy To Use – When there is a power outage, the ATS automatically switches power, no manual switching required.
  • Programmable – Some ATS units are programmable to be able to put a higher priority on more important appliances to prevent overloading.

Cons

Cons
    • Expensive – Compared to manual switches, the ATS is considerably more expensive, however, you get more features.

Best transfer switches: My recommendations

Finding which transfer switch is best for your home will depend on your budget and how easy it is to access your breaker box (or location of switch).

There are many options on the market to choose from that offer a wide selection of different options.

I will look at the top manual and automatic switches for a general guideline on my top picks.

1. Reliance Controls Corporation 31406CRK – Most Popular Manual Transfer Switch

The Reliance Controls Corporation 31406CRK is an Amazon customer favorite for many reasons.

This competitively priced, all in one manual transfer switch kit includes everything you need to safely and effectively transfer power from your generator to your home with ease.

Features:

  • Maximum Running Generator Watts: 7,500
  • cUL1008 Listed
  • 5 Year Product Warranty

This kit includes a pre-wired transfer switch with wattage meters, 10-foot power cord, 30A power inlet box, wire connectors and extra 20A plug end.

Check Price on Amazon

2. EmerGen Switch 10-7501G2 – Great For Indoor Or Outdoor Applications

For versatile applications, the indoor/outdoor compatible EmerGen EGS107501 is the solution.

Many manual transfer switch boxes are meant to be mounted indoors making them out of the question for those needing an outdoor mounted box.

This is where this transfer switch really outshines the competition.

Features:

  • Maximum Running Generator Watts: 7,500
  • UL Listed
  • 1 Year Warranty
Connecticut Electric EGS107501G2KIT EmerGen EGS107501G2 10 Circuit Manual Transfer Switch Kit, Portable Generator for Emergency Use
  • FOR PORTABLE GENERATOR: This transfer kit is designed for use with emergency generators that have up to a 30 amp output, Nema L1430. With easy-to-follow instructions, this unit is incredibly easy to install and is a cheaper alternative to running your portable generator without it.
  • VOLTAGE: This transfer switch kit is designed with the capability of 2 pole circuits and allows 240-volt circuits, making it perfect for well or water sump pump applications. If one of the installed 2-pole circuits are not needed, the tie bar can be removed to allow for 2 single pole circuits.
  • INDOOR OR OUTDOOR: The designed enclosures of the power inlet and transfer switches to be used either indoors or outdoors and have a NEMA 3R rainproof rating allowing the kit to be installed wherever is convenient for you and you home.

The included nema 3R rainproof power inlet box keeps your connections safe while allowing for a versatile mounting location.

Check Price on Amazon

3. Reliance Controls Corporation 51410C For Generators Up to 12,500 Running Watts – Quick And Easy Installation

The 51410C is not only a solid competitor for the fact of being able to be used up to 12,500 running watts.

The simplistic designs allows for a quick and easy installation in both home and office settings.

This manual switch kit features a high quality, powder-coated steel box, six combination knockouts, resettable branch rated circuit breakers and non-defeatable double-throw switches.

Features:

  • Maximum Running Generator Watts: 12,500
  • Designed For Fast And Easy Installation
  • 2 Year Product Warranty
Sale
Reliance Controls 51410C Pro/Tran 10-Circuit Indoor Transfer Switch
  • Designed for fast installation in both residential and commerical applications
  • 18-inch flexible conduit whip easily attaches to load center
  • Maximum generator running watts: 12,500. 15 amp single pole circuit breakers. 20 amp single pole circuit breakers

Check Price on Amazon

4. Generac RTSW200A3 – Most Popular Automatic Transfer Switch

The Generac RTSW200A3 is an all in one automatic transfer switch built to power a whole home or small office.

This 200 amp, 120/240v single phase rated transfer switch features a convenient service disconnect to allow for easy maintenance or repairs.

The Nema 3R rated enclosure ensures your switch stays protected while keeping it easily accessible.

Features:

  • Maximum Running Generator Watts: 48,000
  • UL/CUL Listed
  • 2 Year Product Warranty
Generac RTSW200A3 200 Amp Automatic Transfer Switch 120/240V Single Phase Rated NEMA 3R
  • 200-amp 120-240-volt single phase nexus transfer switch with service disconnect
  • NEMA 3R rated aluminum enclosure
  • Transfer switch connects through the utility meter for easy installation

Check Price on Amazon

How To Wire A Transfer Switch To Your Home

Wiring a transfer switch to your home is a process we suggest leaving up to the professionals, but if this is a task you do not mind tackling yourself, here is a quick overview of the proper steps to take.

Disclaimer
This is a general guideline and I assume no liability for property damage or injury incurred as a result of any of the information contained in this article.

How to Install a Manual Transfer Switch for a Portable Generator | Ask This Old House

  1. Locate your panel box and determine where you want to mount your switch. (Mounting your switch near your panel box is a common practice for easy installation)
  2. Mount your transfer switch to the wall and ensure that it is secure and out of the way of any obstructions or appliances
  3. Locate the main electrical panel of the house and turn off the main power. (Always double check that the power is off by testing appliances)
  4. Properly connect the wires coming from the transfer switch to the breakers you want to control in the panel box.
  5. Using the proper 1 ½” drill bit, drill a hole through the house wall from the outside to feed the electrical wires through.
  6. Install the included electrical box above the hole on the outside of the house.
  7. Run the proper electrical cable from the electrical box, through the hole, to the transfer switch.
  8. Locate the electrical receptacle included with your switch and connect it to the electrical cable at the outdoor box. Mount the electrical receptacle to the box.
  9. Connect the other end of the same cable to the transfer switch inside the home.
  10. Ensure that your portable generator is in working order before testing your work.
  11. To test your work, leave the main power to your home off and plug the generator into the outdoor electrical receptacle.
  12. Flip your transfer switch from line to generator and check that the connected circuits are receiving adequate power from the generator.
  13. If everything is in working order, flip your switch back to the original position, turn off your generator, and turn your main power back on.
  14. Seal up the hole in your wall to ensure weather, bugs, and moisture do not enter.

Conclusion

In conclusion, we hope that this guide has given you the information you need to make your decision on which transfer switch to choose and allowed you to learn how to install it.

A transfer switch is a great investment to help restore power in the event of a power outage where important appliance must keep running.

With the many different styles and applications, I want to hear your first hand experiences.

Have you used a transfer switch on your home? What kind of situations has a transfer switch helped you in?

Last update on 2020-08-03 Affiliate links & images from Amazon Product Advertising API

15 comments

  1. Well, this description leaves me puzzled: With the instructions referring to “turn off the main power” and “turn your main power back on”, it doesn’t sound like such an install has any means of preventing accidental back-feed, which is kind of the whole reason for the switch.

    If this switch only serves to connect the GenSet to a specific set of breakers in the service-entrance panel, those breakers would also have to be switched off to prevent back-feeding the rest of the panel during generator operation.

    Am I missing something?

    With this logic, how would use of a switch in the suggested manner be any different than just wiring the GenSet directly into the main buss and manually throwing the main and the individual circuit breakers for the circuits I don’t want powered?

    I honestly was of the impression that a transfer switch was a dressed-up DPDT switch that physically could not permit simultaneous connection of the public power grid AND the private generator. I also was of the impression that back-feeding the grid (aside from the safety issue of the stray current on an assumed cold circuit) would likely damage the generator or control circuits when the grid was re-energized, due to the lack of phase synchronization.

    Unless the phase, voltage, wave-form, and polarity are all within a small fraction of the grid values, there would be strong adverse current flows.

    If the phase was 180° off, the direct short currect would be at double the generator’s maximum output: That just couldn’t be good.

    1. The transfer switch testing requires you to “turn off the main power” as a means of simulating an outage and allowing the connection to be tested on the GenSet.

      Testing can be completed with the main power energized but will not indicate if you have done the job correctly. All transfer switches are Break-Before-Make switches which will not allow an interconnection between GenSet and the load center.

      With a properly connected transfer switch there is no way to back-feed either power source.

  2. I have an ATS (Generac 200A 120/240 1P NEMAS). Can I hook it up and run a portable generator (15,000kw) through it using a 50 amp hook up plug?

    1. Well it’s kind of overkill, but yes you can but be mindful of the bonding, if your gernerator’s neutral is bonded to the frame it’s a NEC violation as that transfer switch doesn’t transfer the neutral line. Check your generators manual to see if it’s bonded or floating.

  3. Thank you for the information. Am I correct in assuming that I can use a generator rated at 9KW (or higher) with your first transfer switch, which is rated at 7.5KW, provided I ensure that my loads do not exceed 7.5KW? If the answer is no please explain why not. Thank you.

  4. I have a Ford generator rated 9000 running watts , it has a three prong turning lock outlet for 120 volts 30 amp(L5-30) and a four prong outlet 120/240 volt 50amp(14-50) , I bought a Generac transfer switch 50 amp rated only compatible with 120/240 volt generators , the question is what wire gauge should I use between the generator and transfer switch and which outlet should I use in my generator for that?

  5. Thank you for this article.
    I have a question and am not sure who can answer it.
    I have a small portable generator Westinghouse iGen4500DF which does not produce 240V power and has no L14-30 outlet. It only has 2 regular 5-20R 120V household outlets and 1 TT-30 30Amp outlet.
    Are there any transfer switches I can plug it into?
    I only want to run some lights, cable modem, and fridge in a power outage and can get by without 240V during outage.

    1. I’m considering buying this same generator for this purpose and have the same question. Did you ever find out if it could be plugged into a transfer switch?

  6. Concerning grounding! Does the transfer switch (panel) have to have its own ground rod and /or connection to cold water pipes?

  7. Your comments are very helpful! I am interested to find equipment to start a Honda 6KW, electric start generator and operate the transfer switch when the grid goes down.

  8. I have a older generator , 5500w output with two 110 outlets and one 220 outlet is it possible to use a manual transfer with this generator? It doesn’t have the four prong connector type plug that newer ones have.

  9. Until we decided we needed at least a portable generator on hand we had no clue how (somewhat) complicated it would be to actually use! Your article is a lifesaver and now we have the basics! Time to call a certified electrician to have a transfer switch installed!

  10. Can you use an automatic transfer switch on a portable generator with a choke? I had a 16kw Generac which failed after not to much run time. The price to replace the unit was to high to replace. Can I use the same automatic transfer switch on a 13000watt dual fuel duramax which I am going to convert to a trifuel to utilize natural gas and build new housing with ventilation. The problem is the duramax has a choke. Will it work?

    1. following! I am in same boat. I bought the house with a generac “automatic” transfer switch installed already with a big 240 plug outside. the prior owner must have used with a portable generator and took it with them. The transfer switch has around 10 receptacles which is fine but there is no “grid to generator” switch. There is a transfer switch on the main breaker box but its in the on position which seems odd to me since the utility power is on. Unless that is the set up for an automatic transfer switch.

      Thomas why would a choke start affect the connection? just choke the motor, start the motor then plug it in right? I am looking at the duramax 13,000 and hope it will run the AC in a emergency.

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