Transfer Switch
All permanently installed generators must operate through a properly sized and wired transfer switch for safety. A transfer switch isolates the household or farm electric system from the electric utility system. There are several reasons for this requirement.
1) If an emergency generator is connected directly to the house or farm electrical system without the isolation provided by a transfer control, electric power can travel back through the utility service wires and onto the utility power lines. The 240 volts produced by the emergency generator will be boosted by the utility transformer to the distribution voltage level (e.g.,4800,7200, or 12,000 volts or more). Unsuspecting linemen working on a supposedly dead power line can be killed or seriously injured.
2) If the power produced by your generator is allowed to access the utility power line, your generator may energize a neighbor's electrical system and attempt to pick up any electrical load that may not be switched off. This could seriously overload and damage the emergency generator.
3) Finally, without isolation from the utility power line, an operating emergency generator can be severely damaged or destroyed when the utility power comes back on. The utility power will be out of phase (not synchronized) with the generator and will cause the generator windings to be burned up.
There are two types of transfer switches: Manual and Automatic.
Manual transfer switches are used with manually started emergency generators.
Automatic transfer switches are used with engine driven generators that automatically start up when the utility power supply is lost.
Transfer switches need to be sized for the current rating of each service connected to it.
For example, a farm with a 400 ampere main service would require a 400 ampere transfer switch.
There are two considerations for transfer switches for household use. If only selected circuits will be energized by the emergency generator, then those circuits can be wired through a small transfer switch. If the entire house will be energized, then a transfer switch rated for the service size must be used. Your generator supplier or electrician can help you select and install the appropriate device to maintain proper operating safety.
All permanently installed generators need to comply with the National Electrical Code and local electric codes. If local electric code requirements for such installation exceed the National Electric Code requirements, the local code must be followed. It is important to have a qualified electrician provide the electrical installation for a generator. Often, the generator supplier is qualified to handle the entire installation. Don't attempt a do-it-yourself installation unless you are fully qualified and understand all requirements of the installation.
Permanently installed generators require plenty of open air space and good ventilation to carry away heat produced by the generator. Never install or run a generator in a tightly closed room. Excessive heat and carbon monoxide will create a very dangerous situation.
Permanent household generators are usually installed outdoors in a specially designed shelter that provides weather protection and adequate ventilation while the unit is operating. If a portable generator is used, it should be wheeled to a location near the house service entrance where a lead from the transfer switch can be attached to the generator output. The portable generator should be properly grounded, using the grounding tap provided on the generator control box. Never operate the portable generator in the basement or garage. The carbon monoxide produced by the engine is deadly.
There are numerous maintenance issues to consider. Follow the manufacturer's maintenance recommendations and schedules. A little time spent on preventive maintenance will assure that the generator will operate properly when you need it. Self contained engine generators require numerous maintenance procedures. Engine oil and fluids must be checked regularly and changed at recommended intervals. Batteries must be kept fully charged and battery terminals need to be kept clean and treated with anti-corrosion material. Fuel filters must be maintained and fuel should be fresh to facilitate quick starting and adequate power output. Keep the fuel tank filled. Often, engine generators don't start simply because no one checked and filled the fuel tank after the last use. Engine generators should be started and operated under load at least once per month for at least 30 minutes. A regular exercise period can be programmed for automatic generator systems.
By following proper operating and installation procedures, performing regular maintenance and observing all safety rules, an emergency generator will perform effectively and safely for years to come.