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Transfer Switch Sequence of Operations

There is no question about it; lightning is potentially the most destructive force your generator and automatic transfer switch are likely to encounter. When it happens, two things should come to mind: 

1.How to prevent a reoccurrence

2.How to repair the damage

While you cannot stop a lightning strike, you can take steps to minimize the damage your equipment might incur and make your facility a less likely target. 
There is more information on lightning, lightning damage and other related topics at The Weather Channel's Lightning Link. 

How to prevent a reoccurrence

Probably the most common way lightning causes damage is through a high voltage surge carried in by the electrical power lines. If lightning hits power lines or hits the ground close to a power line even many miles away, it can induce a high voltage surge in the lines that feed your facility. 

Since most modern automatic transfer switches constantly monitor the utility power and use solid-state components, they are exposed to damage from this source. Some models even allow the surge to pass on out to the generator control panel and thus double your trouble. Fortunately, if you install a simple surge protector at the automatic transfer switch or as close to the main utility entrance as possible, you can divert most high voltage spikes to ground before they cause damage. 

Surge protectors are simple, cost effective, and easy to install. 

First Preventive Step:

Install an appropriate surge protection device at or near the main utility entrance.

(NOTE: If you already have an emergency generator, you may go on to your emergency system before a thunderstorm arrives. By doing this you will have disconnected sensitive equipment from the utility. This is the best way to avoid transient spikes. See our page on how to do this.) 
 
 

Much of the lightning damage I repair is not the result of a direct hit on a generator. Rather, it comes into the generator or automatic transfer switch as a high voltage surge through a utility connection or as a charge seeking ground after a lightning strike on a tower or other large piece of equipment.

When lightning hits something, it transfers a huge number of electrons to it; thus creating a high potential (voltage) between that object and earth ground. Generators are usually low to the ground and therefore not good targets for direct lightning hits. But they often sit next to communications towers or heavy machinery that does attract lightning. When the neighboring equipment takes a hit, the electrons it receives bleed off into anything between them and ground. This could be your generator! As they pass through, electronic components are often damaged. 
 
 

Second Preventive Step:

Thoroughly ground everything. Make sure grounding cables and grounding fields are large enough. Make sure all grounding connections are tight. (See our link to Grounding for more information on how to properly ground your equipment)

The third and fourth areas of concern are the telephone and cable TV wires that connect to facility. Some customers use these for signaling purposes to give warning of low fuel condition, power failure, engine failure, etc. These utilities can deliver a high voltage spike to your equipment just like the electric utilities can. 

During a thunderstorm or if I am going to be away, I always disconnect my computer from the telephone lines and my TV from the cable. This is the best protection. But if that is impractical, there are many surge protectors available for telephone lines and cable TV.  

Third Preventive Step:

Disconnect sensitive equipment from phone and cable TV lines during thunderstorms.

A note about cheap surge protectors: There are many surge protector strips and other types of small protectors that you plug into a standard wall outlet. They work. Kinda—Sorta. For a little while. But only for a little while. 

These devices generally work by connecting a variable resistor across the line to ground. For them to work you have to have a well-maintained properly grounded wall receptacle. Even if you do have a proper receptacle the variable resister will only take a few small hits before it opens up completely. The power strip will continue to work and the light will stay on (The light on most of these power strip protectors has nothing to do with whether the surge protection is intact) but it will, after a few hits, provide no surge protection. If you are going to use them, replace them every 30 days with new ones. You might get some protection that way. Also, a powerful surge will instantly destroy the variable resister but the power strip and light will continue to give you false hope. 

This is another one of those things that looks like it "oughta" work but it doesn’t. 
 
 

How to repair the damage
 
 

A direct lightning strike can damage anything. I have seen automatic transfer switches blown completely off the wall. But we seldom see a direct hit on an emergency generator or automatic transfer switch. Most damage comes from a high voltage spike that takes a toll on the solid-state control circuits. 

ONAN

The Onan OT III automatic transfer switch is great at surviving. Damage is usually minimal. Primary areas I find damaged are the Program Transition Board, K1 and K2 relays, transformer board, and T1 transformer. If any of these are damaged they need to be replaced. Any good maintenance guy can make the repair. It is usually a simple component swap. Contact us for diagnostic procedures, wiring diagrams, and parts. Talk to a technician any time 1-800-888-4594.

The Onan LT, OT II, OT, and AT switches are a bit more complicated and some models are no longer factory supported. We can supply diagnostic help for these as well as wiring diagrams and parts. 

When the generator controls are damaged, the unit won’t start, run, or shut down properly. The most common Onan controller is the Detector. Lightning often causes it to shut down on "overcrank" or "overspeed" even before it starts. Another symptom is a blown F4 fuse. This board is easy to replace. Call us for help. 

The Onan PCC panel requires special testing equipment and diagnostic procedures. Again, we can help. We will rent the tester to you for a nominal fee and provide diagnostic help and parts. 

Kohler

Kohler automatic transfer switches also use solid-state controls. Most components are consolidated into one motherboard. This, when damaged, requires complete replacement. Call us for diagnostic help and parts. 

The Kohler engine controller may also be damaged. Symptoms include shutdown on "auxiliary" fault or the inability to reset from any fault. We can provide diagnostic help, the Kohler "Fast Check" diagnostic tool kit, wiring diagrams, and parts. 

Generac

Generac automatic transfer switches use a solid state "logic’ board, exerciser clock, and voltage sensor. These components as well as the limit switches L1 and L2 in the contactor assembly on the "Y" type switch are subject to damage. If the limit switches take a hit the high voltage may be transmitted out to the generator where it can damage the voltage regulator, voltage adjust rheostat, field flash diode, and crank-latch board. 

The Generac generator B and C panels are subject to damage in more areas than most because of the way they are tied together. All of these components subject to damage are replaceable by any good maintenance guy except for the contactor assembly in the transfer switch. The contactor assembly may be sent to us for repair but it must be removed and reinstalled by a licensed and qualified electrician.
 
 

PHH 

7/9/99