OK, let me throw in my 2cents worth, as an electrical contractor and master
electrician. I install generators for a living (or at least part of it).
Joe Foley and Joe Young are both correct.
Joe Foley's comments about the starting load is probably your biggest problem
is right on. A 10 KW generator will put out a maximum of 83.33 amps at 120
volts and 60 cycles. BUT the starting load of a motor driving any kind of
compressor, or pump will EASILY exceed 400 % of it's normal running load.
Some types of motors can exceed 600% of normal load, while they are starting.
If you look at your refrigerator, freezer, or heat/airconditioner compressor
it will generally give your the load on the nameplate. Multipy this by at
least 400% for starting. This load will only last a few seconds, but if the
generator can not (or will not) generate this amount of current, the motor
will just sit there, trying to start and burn up. If you can not find a
nameplate rating for full load amps (listed as FLA on the nameplate), look
for the horespower rating. Multiply this by 746 watts per horsepower; thus a
5 hp motor will draw approximately 3730 watts running - but up to 15,000
watts when starting. Notice that 15,000 watts is greater than 10,000 watts
or 10KW. Results are that you will let the smoke out of the motor and it
will quit.
Joe Young's comments about the switch in the line is also exceptionally good
advice. This both prevents someone from the power company from touching a
line that YOU have made hot, and causing an injury, and it keeps your small
generator from trying to feed the entire neighborhood at the same time. If
you don't have a switch to disconnect the generator from the normal service,
the power from your generator flows "backward" through your main panel,
throught the meter and back up the pole to the main transformer, then flows
backwards through the transformer going from 120 volts up to 15,000 volts,
then on down the line to your neighbor's house. Results of this are that
you're going to let the smoke out of your generator and IT will quit working.
The simplest (but most expensive) way is to use an automatic transfer switch
that get's it's normal power from the main source, but will switch over to
the generator when the normal power goes off. You can do this several ways
(cheaper) but it requires turning off one, and turning on the other. A
friend of mine built a new house, and installed a small 6 circuit panelboard
beside his main panel. He then used a standard range cord to plug into a
receptacle powered by the main power panel. To this smaller panel, he
connected his refrigerator, freezer, and a few lights. This runs normally on
the main power but when the power fails, he can unplug the range plug and
plug it into his generator circuit. Works the same as a $1,500 transfer
switch but it is NOT automatic.
Good luck with your project. Tom Campbell - Birmingham, Alabama
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