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Posted by Bob S. on August 5, 2005, 9:27 pm
I'm trying to figure loading for a generator. Manufacturing labels on
many appliances (a/c, refrig, freezer, etc)list a current rating, like
13A, 7A, etc. Are these ratings peak current at startup, or average run
current? If it's peak, does the formula I avg = .707I peak still
apply? I notice the generators average wattage is about .65% of the
surge wattage, but I figure that's a safety margin, right?
Bob S.
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Posted by Ralph Mowery on August 6, 2005, 11:26 am
> I'm trying to figure loading for a generator. Manufacturing labels on
> many appliances (a/c, refrig, freezer, etc)list a current rating, like
> 13A, 7A, etc. Are these ratings peak current at startup, or average run
> current? If it's peak, does the formula I avg = .707I peak still
> apply? I notice the generators average wattage is about .65% of the
> surge wattage, but I figure that's a safety margin, right?
>
> Bob S.
>
The appliance lable current is the average current the device will use under
its rated load. That is for devices that are on all the time. Things like
a refrigerator will draw lots more current while starting for a few seconds,
then draw the average current listed on the lable and then cut off and not
use any current or maybe a very small ammount. Devices that have motors
will take a large ammount of current to start up and then drop back to the
name tage value. Do not worry about the .707 value and such in formulars ,
just use the value listed. The surge value listed on the generator is to
allow for a short period of high current. The average wattage of the
generator is what you need to look at and not worry about the surge current.
That is mostly for advertising.
As most generators will have a 120 volt and 220 volt outlets, remember to
try and ballance the current off each side of the two 120 volt circuits.
The total wattage for the generator is for the 220 volt outlet. That means
that if you have a 4000 watt generator you can only use about 2000 watts off
each of the 120 volt outlets or each side of the 220 volt outlet. In other
words there is one winding connected to the 220 volt outlet and it is the
same one with a center tap that is going to the 120 volt outlets.
If you have a large load on the generator and need to start a motor such as
a well pump youmay need to take some of the load off to get the motor
started and then you can put the othe load back on.
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Posted by FDR on August 6, 2005, 12:12 pm
> I'm trying to figure loading for a generator. Manufacturing labels on
> many appliances (a/c, refrig, freezer, etc)list a current rating, like
> 13A, 7A, etc. Are these ratings peak current at startup, or average run
> current? If it's peak, does the formula I avg = .707I peak still
> apply? I notice the generators average wattage is about .65% of the
> surge wattage, but I figure that's a safety margin, right?
>
> Bob S.
>
I suggest you visit the websites for Coleman, Yamaha or Honda generators.
They have load calculations and lists of power draw for most household
devices.
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Posted by Stormin Mormon on August 6, 2005, 1:04 pm
It's my understanding that the amperage ratings on appliances are full load,
after the device is running.
The couple times I've measured a window AC, it's been 25 to 40 amps to get
it started, and then 8 or 9 to keep it running. About that much.
How about an actual use test? I had some gas left in the generator (Coleman
2200 watt) and for curiosity tried it on my living room AC. 10,000 bTU with
a rotary compressor. Worked nicely. As expected, ran through fuel pretty
fast, which was what I wanted. Wanted to run the tank dry so I could put the
generator away.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com
I'm trying to figure loading for a generator. Manufacturing labels on
many appliances (a/c, refrig, freezer, etc)list a current rating, like
13A, 7A, etc. Are these ratings peak current at startup, or average run
current? If it's peak, does the formula I avg = .707I peak still
apply? I notice the generators average wattage is about .65% of the
surge wattage, but I figure that's a safety margin, right?
Bob S.
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Posted by Bob S. on August 6, 2005, 8:13 am
Stormin Mormon wrote:
> How about an actual use test? I had some gas left in the generator (Coleman
> 2200 watt) and for curiosity tried it on my living room AC. 10,000 bTU with
> a rotary compressor. Worked nicely. As expected, ran through fuel pretty
> fast, which was what I wanted. Wanted to run the tank dry so I could put the
> generator away.
Which brings up another question - gas stabilizers. The generator
instruction book states that if you use a gas stabilizer in the fuel,
it can remain in the tank for "up to 2 years". Gas stabilizer
manufacturers make the same claim. Does the stuff really work that
good???
Bob S.
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