Emergency/backup Generators
Backup generators come in many different sizes. Some generators are stationary, mounted on cement pads whose sole purpose is to provide electricity in the event of a power failure. Other generators are on wheels so they can be used in different places and not for the sole purpose of back up power. The type and size of generator that you need will be dependent on many different factors. Before we talk about generators, we should first discuss the transfer switch.
Transfer switch
The transfer switch is responsible for isolating the circuits, that the generator supplies, from the main power grid. This is necessary so the generator does not "back feed" the main power grid causing damage to the generator and possibly bodily injury to a line worker. There are two main types of transfer switches, manual and automatic.
The manual transfer switch is normally used with a mobile generator. Normal mode of operation is as follows:
· Generator is wheeled outside and started
· After generator has warmed up, it is connected to the transfer switch
· Transfer switch is switched from "line" to "alternate" power.
When line power has been restored, this order is reversed. The major advantage for this type of the manual transfer switch is cost. The manual switch can cost 3 to 5 times less than the automatic switch. The major down fall to the manual switch is the fact that it will take some work to set it up and get the generator running in the event of a power failure. This should be taken under consideration when choosing a generator transfer switch.
The automatic transfer switch is normally used in combination with a stationary single use generator. There are two main functions of an automatic transfer switch:
· Transfer the load to the generator in the event of a power failure
· Excise the generator ever one or two weeks to keep the fluids fresh
The only worries an owner has with an automatic transfer system is to make sure the generator is serviced every year and that it has fuel. Most residential generators run on propane or natural gas. The gas companies will put the owner on a refill schedule so fuel should not be a problem.
Sizing a residential generator
The following is just a simple guideline to sizing a back up generator. This should not take the place of having a qualified electrician size up a generator for your specific application. There are many factors involved in pick the most appropriate size for your home. The bare minimum size generator should be a 6500-watt continuous for a whole house application. Make sure that the rating is continuous and not a intermitent raiting. A 6500 watt generator should be large enough to power some lights, run the furnace (fuel fired and not a heat pump), and run the well pump intermittently. If you can afford an 8000-watt generator, you could expect to operate your house normally except for the use of electric ranges (the use on one burner should be fine) and electric clothes dryers. The most common type of generator that we install is a 12Kw standby generator. This generator will allow normal house operation as long as an electric cook top, stove and clothes dryer are not used simultaneously.
There are many caveats to the NEC 2005 electrical code with respect to generator installations. I would not recommend homeowners trying to install the generators or the transfer switches. I would also recommend that you let your electrician purchase the generator and switches. His equipment might cost more up front than the generator sets you can find at the local home improvement center, but your electricians familiarity with the products he is used to working with will be worth it in the long run. You will have the peace of mind knowing that if something goes wrong, you can call your electrician and they will have no excuse but to make it right.
If you would like Daley Electric to help you with your generator needs, please do not hesitate to call us at 603-569-4515 or email us at info@daleyelectric.com.
