Motor starting current; genset capacity

I've got a 3/4 HP pump motor that's rated for a 32 amp starting, 9 amp nominal current req'mt at 230 VAC, single phase. The manufacturer recommends
a 20 amp breaker.
The essential question is what the minimum watt/amp reqm't of a generator needs to be to start and run this pump. Am I correct that at surge capacity of at least 7.5 Kw is req'd to meet the starting current reqm'ts of the motor or am I thinking about this wrong ? Would a 2.5Kw genset work, for example?
I'm not sure I understand how electric motors start and why a 20 amp circuit breaker would work when the starting current exceeds the breaker rating and also how a genset would respond to a momentary surge-draw.
As always, TIA ...
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starting, 9 amp

manufacturer recommends

of a generator

surge capacity

reqm'ts of the

genset work, for

a 20 amp circuit

breaker rating and

the breaker will take the surge.... the generator capacity is the generator capacity and if you ask more if it, you wont much... a short blip.. thats it... the drive motor is maxed...it has no surge capacity.
If you want ot close off the pump discharge or suction (yes discharge if is a single stage single impeller pump, most comon except for wells) the pump will start with much less amperage draw and free wheel. So even with the small generator it might get rolling..and come up to speed, then you can open the valve.
Phil Scott

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recommends
capacity
circuit
and
Not enough information to really answer the question. Motors can draw 6 times FLA on start 9X6 T amps. Not knowing what kind of pump or head on the pump there is no way guide you.
the 2.5kw might start the motor, with out an load for a while. Your pushing it really hard.
The 20 amp is all that is needed for the motor as the starting current is only a few cycles. Most generators will try to carry the load. Sometimes they run into a brick wall and then the genset shorts out and your left with an noise maker. Look into an softstart for your application. Might be cheaper than an larger genset than you need. Especially when you consider the fuel and maintenance.
Oversizing the wire when on the genset will help a little. Voltage drop is very important when starting an load. I.E. run #10 gauge stranded to the motor instead of the #12.
Gensets have an finite amount of power. The utility is almost and infinite amount.
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The pump is rated for 5 gpm at 400' head. It's set at a depth of 210' and the elevation difference b/t the well-head and the house is 0'.

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My simple mind wants it to be true that 1/2 the head equals 1/2 the load equals 1/2 the starting current.

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starting, 9 amp

manufacturer
reqm't of a

that at surge

reqm'ts of the

genset work, for

why a 20 amp

breaker rating

surge-draw.
knowing what kind

while. Your

starting current is

they run into a

noise maker.

cheaper than an

the fuel and

little. Voltage drop

stranded to the

almost and

(http://www.grisoft.com ).
10/8/2004
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snipped
kind
snipped again

Sorry dude with that much of an head your talking seconds of locked rotor current on the motor. Your genny will never handle it, if it does it will not for very long. With that much head the soft start will have to be pushed out a lot farther in time than I would want for my pump. Before looking into the softstart better check with the manufacture of the pump to see how the pump will handle the situation. As a wild assed thought have you considered an 2 speed motor? Start on low, get the water moving then move to high. Again check with the pump manufacture about doing this before doing it.
Bottom line you need an bigger gen set. Unless you really into creating an monster that no one but you will be able to handle. What about the SO when your not around and this needs to work?????
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starting, 9 amp

manufacturer
reqm't of a generator

at surge

reqm'ts of the

genset work, for

why a 20 amp

breaker rating

surge-draw.
knowing what kind

while. Your

starting current is

run into a

noise maker.

cheaper than an

the fuel and

Voltage drop is

stranded to the

almost and infinite

10/8/2004
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Well, I was planning on converting my gas generator to propane, but I'm not sure that this solves anything. The rated capacity of the genset is twice the nominal current reqm't of the pump but only half of the starting current.

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that
current
2.5Kw
and
the
they
an
consider
little.
gauge
(http://www.grisoft.com ).
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wrote:
| Go with a propane or natural gas fuelled gen set if you want | stable stand by capability go one size larger...Genrac might | make one that small.
Smallest Generac on NG or LP is 7 kW. But I think he needs at least that big, anyway. Next size up is 10 kW commercial model and 12 kW home model. Kohler models start at 10 kW.
A neighbor has a 5.5 kW gasoline generator, and his big screen TV won't run on it at all. But on utility power, that TV blinks half the lights almost to zero for a very brief instant to get the TV on. I think he needs a bigger genset. I'm trying to talk him into a 25 kW NG model. Then he can have some hot pizza while watching TV in the big blizzard (if his dish doesn't ice up).
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You need a soft start controller such as: http://www.baldor.com/products/specs.asp?1=1&catalog=S23CA&product +Controls&family=SoftStart%7Cvw%5FACControls%5FSoftStart
Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz
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