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In this article we
will try to find accurate answers of some important questions about generator
transfer switch.
What is
a generator transfer switch and why do I need one?
A transfer switch is
the key to safe and convenient operation of portable generators for backup
power. A manual transfer switch isolates those circuits using generator power
during an outage, and eliminates the risk of back feeding the electrical
utility which can cause injury to utility workers and property damage. Using a
transfer switch for backup power also eliminates the need to run extension
cords around the home or office to operate certain appliances.
How does a small transfer switch tie into my circuits?
A transfer switch transfers the load after the branch circuit breakers on the load side of the circuit. This allows the transfer switch to be installed without the labor and expense of moving the branch circuit breakers to another panel. It further allows the transfer to be made using a "light switch" type of toggle switch rather than switching a series of circuit breakers. Finally, a transfer switch can feed some of the circuits from the utility and others from the generator.
Why
can't I just run extension cords from my generator to my appliances?
This can be done as long as no connection exists between the generator and the utility and the appliance and the utility, i.e. there is no chance of back feeding the utility. The advantage of a transfer switch over cords is that you can run devices that are not cord connected such as a furnace blower motor or wall and ceiling light fixtures. A transfer switch provides the convenience of utility power and eliminates the need to run extensions cords throughout the house. A transfer switch with meters can also help in managing power and balancing the generator load to make sure you maximize the available generator power.
Are most small transfer switches automatic?
NO. They are manual transfer switches designed for a homeowner or small business owner to use with a 5000-12,000 watt standby generators.
Are transfer switches pre-wired?
YES. Most small transfer switches come completely pre-wired with a Red and Black wire for each circuit, plus a White neutral and Green ground wire. A 6-circuit unit has a total of 14 wires and a 10-circuit unit has a total of 22 wires, and so on.
I want to connect my well pump to my generator via a transfer
switch. How many 2-pole circuits (commonly called 220, 230 or 240 volt) are
provided on each transfer switch?
Generally the 6-circuit models can be configured for one (1) 2-pole circuit for use on one 240-volt circuit, and are provided with one (1) handle tie. The 8-circuit models can be configured for up to four (4) 2-pole breakers, and one (1) handle tie is provided. The 10-circuit models can usually be configured for up to five (5) 2-pole breakers, and two (2) handle ties are usually provided.
Additional handle ties can be purchased from the factory. See the replacement parts list.
If no 240 volt circuits are needed, the handle ties may be removed and discarded.
What type of connection is required to connect my generator
to my transfer switch or Power Inlet Box?
A 4-wire, twist-lock connector is needed. We have all-rubber Power Cords with a male connector on one end and a female connector on the other end. 12 gauge wire is required for 5000 watt models, and 10 gauge wire is required for 7500 watt models.
Can I use a transfer switch on any 20 amp circuits in my
house?
Yes. The switches and wires in each transfer switch are rated for 20 amps. However, in the generator mode, each circuit is limited to the amperage of the circuit breakers in the transfer switch. Some of these breakers are 15 amps and some are 20 amps. The circuits with 15 amp transfer switch breakers can be connected to either 15 or 20 amp circuits in the main panel. The circuits with the 20 amp transfer switch breakers must be connected to 20 amp circuits in the main panel. The 6 circuit models have a total of two 20-amp breakers and four 15-amp breakers, the 8 circuit models have a total of two 20-amp breakers and six 15-amp breakers, and the 10 circuit models have four 20-amp breakers and six 15-amp breakers.
What is the maximum load on EACH LEG?
The watt meters on a transfer switch allow
you to balance the load on EACH LEG in order to
gauge how much capacity is being used and to maximize generator performance.
See the chart for each series to see what the actual limits are. Generally, see
the typical switches below.
20 (5000 watt) amps for the 6-circuit.
|
30 (7500 watt) amps for the 6-circuit.
|
30 (7500 watt) amps for the
10-circuit.
|
30 (7500 watt) amps for the 8-circuit.
|
No meters are needed for balancing on the 4-circuit models
since they have only one leg. On other models, watt meters can be added by
installing the optional Watt Meter Panel.
|
Can I connect my water heater, electric range or central air
conditioner/heat pump to a transfer switch?
Yes. Items such as a water heaters, central air conditioners or electric ranges can be powered through a transfer switch if the breakers used to control these appliances are adequately rated. Do not try to run these appliances on underrated switches or breakers or you will burn up the wiring, weld the switches, trip the circuit breakers and you will void the switch warranty.
What type of connection is required to connect my generator
to the transfer switch or Power Inlet Box?
A four-wire, twist lock connector is needed. Companies supply suitable power cords with a male connector on one end and a female connector on the other end. The four wires consist of two 120-volt "hot" lines, one neutral and one ground.
Can I hard-wire my transfer switch instead of using a power
cord?
Yes. Even the cord-connected models can be hard-wired. Use the cover plate supplied with every unit to cover the inlet hole.
A qualified electrician may be able to install different standard transfer switches in a hardwire configuration, however, this will void the UL (Underwriter's Laboratories) and CSA (Canadian Standards Association) Listings, and will therefore void the warranty. In addition, if an accident occurs with a unit that has been improperly installed (voiding the UL listing), this may void any insurance claim made after the accident.
Can I use a generator whose wattage exceeds the wattage on
the Transfer Switch?
YES. But this is acceptable for peak wattage but not recommended for running wattage. . As long as you do not pull more than the maximum wattage through the transfer switch at one time while in the generator mode. The two watt meters can help you determine how much wattage you are using, and can help you balance the load on each leg in the generator mode. Pulling more than the rated wattage through the transfer switch could burn out the watt meters, burn out the neutral wire, overheat the main wiring in the transfer switch and cause a fire. To insure proper safety precautions, a suitable double pole breaker should be installed between the generator and the transfer switch when the running wattage of the generator exceeds the rating of the transfer switch.
What happens when the Utility Power is restored?
When your utility power is restored, other lights and appliances in your home (not connected to generator power) will turn on, alerting you go to the transfer switch and flip the switches back to "LINE" mode and shut down your generator. Since those circuits using generator power are isolated from the rest of the house, there is no danger of back feeding the utility power.
How long does it take to install a transfer switch?
About an hour by a qualified electrician familiar with residential wiring electrical codes. If installed with a power inlet box, the installation could take slightly longer. Since each unit is pre-wired, the installer simply needs to determine which circuits will be needed in an emergency/outage, wire each set of wires in the transfer switch to those circuits, install the neutral and the ground, and test the installation under load.
Why are generators rated in watts when most electric tools
are labeled in amps?
Generators are rated by output in wattage which takes into
account the amperage at both 120 and 240 volts. NOTE:
Volts x Amps = Watts (i.e.: 10 amp motor x 120 volts = 1200 watts continuous +
starting watts) OR Watts/Volts = Amps.
Can I make a splice in my main breaker panel?
Yes. Under most conditions. Article
373-8 of the National
Electrical Code (NEC) states "Enclosures for switches or over-current
devices shall not be used as junction boxes, auxiliary gutters, or raceways for
conductors feeding through or tapping off to other switches or over-current
devices, unless adequate space for this purpose is provided. The conductors
shall not fill the wiring space at any cross section to more than 40 percent of
the cross-sectional area of the space, and the conductors, splices, and taps
shall not fill the wiring space at any cross section to more than 75 percent of
the cross-sectional area of that space."
Which Power Inlet Box can I use with a transfer panel?
You may use any Power Inlet Box up to 50 amps that are
available through your supplier.
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