Transfer Switch Basics

There's no doubt that many areas of the nation's power grid 
infrastructure are aging, on the verge of failure. If your livelihood, 
like mine, depends on the availability of power, there's reason for 
concern.<br><br>And the health, safety and well-being of your family 
depends on electrical power as well. Perhaps the best way to prepare is 
to have an emergency backup power plan prepared. Generac Power Systems

Steve Maurer, IME

There's no doubt that many areas of the nation's power grid infrastructure are aging, on the verge of failure. If your livelihood, like mine, depends on the availability of power, there's reason for concern.

And the health, safety and well-being of your family depends on electrical power as well. Perhaps the best way to prepare is to have an emergency backup power plan prepared.

Two options exist — temporary or portable power generators, and permanent generators. I'll talk more about them in another article.

But, the subject here is an oft forgotten part of that backup plan: transfer switches. When hooking up temporary power for an outage, you must make sure it's safe for all involved, including emergency crews working to restore power.

That means the installed device must be installed properly, approved to comply with NEC® Article 72 and NFPA standards and regulations. Manual transfer switches are manufactured to cover that when properly installed. Basically, the power from the generator must not be able to backfeed into the grid under any circumstances.

Period.

Failure to ensure that requirement could result in fines and even jail time should a lineworker be injured or killed. Don't take a chance with their lives. Got it?

Best practice, and the requirement in many jurisdictions, is that the transfer equipment be installed by a licensed, qualified electrician. Might cost more... but it's the safest way to handle it.

Manual transfer switches provide emergency power to selected circuits in the home. How many and which ones depends mostly on the load capability of the portable generator. A 5,000-watt generator will handle a larger load than a 3,500-watt model. Thus, potentially more circuits.

Lighting is not normally an issue. However, motor driven appliances and heat generating devices will cause intermittent to constant load drains. When we experienced a major power outage a few years ago, you'll not believe the appliance that "dimmed the lights" the most.

My doggone coffee maker!

Considered buying a gen just for it! Just kidding.

I've seen two basic configurations for manual, dedicated circuit switches, with bells and buzzers for both. In one, the backup panel is fed from a breaker in the main panel during normal operation. The breakers for the selected circuits are removed from the main panel and fed entirely from the backup panel (acting as a sub panel).

When the power outage occurs, a rocker switch in the backup panel is pushed to the generator position and the temporary power energizes the selected circuits. And indicator light signals the status.

In the other, the wire is removed from the original panel breaker and a wire from the designated backup breaker spliced to it. Another wire from the same backup panel breaker is landed on the original breaker. The backup panel is not fed from a breaker in the main panel.

Switching in that case is accomplished by flipping a switch in the backup panel for each circuit, isolating the selected circuits from the main panel and routing the power from the generator.

In both cases, the backed-up circuits are isolated from the main panel circuitry. If the power to the home is restored, the generator-powered circuits will not backfeed into the line, even with the generator feeding the backup panel. The generator can be shut off and the circuits reconnected to the main panel power with the flick of a switch.

Depending on the model, manual transfer switches can supply power for 6 to 16 circuits. Remember... this is an emergency situation and not all circuits are necessary (although which ones are may be disputed by various family members).

Eventually, you may want to upgrade to a permanent generator to allow for more circuits, even whole house backup power. If you think that's possible, there are some manual transfer models that can easily be upgraded to automatic transfer switches with increased load capacity, up to 1100 kW.


Photo courtesy of Generac Power Systems

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