Oil & Fuel Kohler 30KW standby generator

[wrede]

There is no marketing department involved in converting hp to kw. These are simply two different units of power, and the exact conversion ratio can be found in any technical manual or on internet sites. 52 hp is 38.7 kw, and so with a rule of thumb of allowing 20% losses, the net output is 30.96, still more than the 30 kw rating. I'd certainly agree that no one should run a 30 kw standby generator at the rated load for any long period of time. Starting loads on electric motors or other devices can be much higher than running load, and so the size should be chosen with a substantial reserve in mind. The average running load factor was in the 25-30% range.

 

[NC tractor driver]

wrede 52HP only equates to 26 KW and not the 38.8 KW you posted.

Gale,
The equation to convert HP to kW is:

kW = 0.745699872 ﾗ HP

Substituting you get:

kW= .745699872 X 52 = 38.78 kW

Simple equation converting HP to kW.

 

[JB4310]

I'm in no position to argue math or science, but all the specs I've seen for generators show 2 hp for each KW of continuous output.

Look up Generator Joe, a web site for generator sales.

http://www.generatorjoe.net/html/baldor/products.pdf

The first half of this large list shows consistent use of that 2hp/kw formula.

I can't say every single one cause towards the bottom of the list shows less hp required on the larger gen-sets, but that may be surge rating?

JB

 

[Gale Hawkins]

Gale,
The equation to convert HP to kW is:

kW = 0.745699872 ﾗ HP

Substituting you get:

kW= .745699872 X 52 = 38.78 kW

Simple equation converting HP to kW.

Sorry tractor driver you missed it by a country mile.

You are not the only one pushing bad generator dope today however. The link just posted from generatorjoe will help you see it takes 2 HP to get 1 KW of output. There are some of the marketing folks using your math however.

Using HPx.80/2 will give you soild functional values to expect out of the standby class of gas generators. Now when you get into the 400-4000 HP generators your math might start to be valid.

 

[5030]

...Now, if I could just get a new cabinet for my Guardian 17KW unit, I'd be happy.

 

[RaydaKub]

Sorry tractor driver you missed it by a country mile.

You are not the only one pushing bad generator dope today however. The link just posted from generatorjoe will help you see it takes 2 HP to get 1 KW of output. There are some of the marketing folks using your math however.

Using HPx.80/2 will give you soild functional values to expect out of the standby class of gas generators. Now when you get into the 400-4000 HP generators your math might start to be valid.

I believe you're both correct technically. 746 watts is equal to 1 hp. That's the direct energy conversion figures. But in this thread, we're talking about generators and loads. These generators are nowhere near 100% efficient**, so there is some loss. The next thing to consider is that the maximum voltage does NOT occur at the exact same time as the maximum current flow. When I was in school studying this stuff, we didn't refer to watts (V * A), we calculated volt-amperes which turned out to be a higher value because of the fluctuations in the flows. So if you multiply the volts times the amps at any give time, you'll probably exceed the 1kw rating, but you need that horsepower to achieve it.

** Clarification: Electrical to electrical conversions are very efficient, but a gas engine powering a generator is probably not. The more I've thought about it, the bigger discrepancy is the phase angle of the voltage and current flow, as I described previously.

 

[RavensRoost]

I believe you're both correct technically. 746 watts is equal to 1 hp. That's the direct energy conversion figures. But in this thread, we're talking about generators and loads. These generators are nowhere near 100% efficient**, so there is some loss. The next thing to consider is that the maximum voltage does NOT occur at the exact same time as the maximum current flow. When I was in school studying this stuff, we didn't refer to watts (V * A), we calculated volt-amperes which turned out to be a higher value because of the fluctuations in the flows. So if you multiply the volts times the amps at any give time, you'll probably exceed the 1kw rating, but you need that horsepower to achieve it.

** Clarification: Electrical to electrical conversions are very efficient, but a gas engine powering a generator is probably not. The more I've thought about it, the bigger discrepancy is the phase angle of the voltage and current flow, as I described previously.

Volts * Amps = Volt Amps and is good for a quick and dirty, but power is Volts * Amps * Phase Angle. (Phase angle is usually inductive and in the 0.8 to 0.9 range, closer to 0.8 if the load consists of a lot of motors or lighting ballasts (not electronic ones though). If the load is 100% resistive then V*A really does = Power [because phase angle of a resistive load is 1.0])

Also in the discussions above about HP per KW of generator load, need to remember various derating factors such as altitude and ambient temp, so a mfg may well spec a more powerful engine to cover all possible derating.

 

[RaydaKub]

Exactly! I remember my professors pointing out to us that if you want to drive the power company crazy, just hook up a bunch of big coils to your AC. They'll have to provide full voltage and current flows, but the watts would actually be close to 0.

 

[Gale Hawkins]

Volts * Amps = Volt Amps and is good for a quick and dirty, but power is Volts * Amps * Phase Angle. (Phase angle is usually inductive and in the 0.8 to 0.9 range, closer to 0.8 if the load consists of a lot of motors or lighting ballasts (not electronic ones though). If the load is 100% resistive then V*A really does = Power [because phase angle of a resistive load is 1.0])

Also in the discussions above about HP per KW of generator load, need to remember various derating factors such as altitude and ambient temp, so a mfg may well spec a more powerful engine to cover all possible derating.

Thanks guys. I knew it took 2HP+ but did not know the math behind the practical fact of life. :thumbsup:

 

[JoeL4330]

I have a 15KW Generac powered by the Kohler LP engine and, yes, it uses oil and my dealer/servicer says check oil every 24 hours. Once, when I was away, it ran for 100 hours straight and was just about down to the low-oil shutoff point. The oil capacity of those engines is very small (2 qts.!) ...in discussion w. service rep, he mentioned that they had a 17KW unit, with higher HP Kohler but same small oil sump.

Air cooled engines, pushed to the limits, run hot and burn oil ...interestingly, just noticed that Kohler offers what looks like a retro-fit oil cooler, see attached, which it claims will reduce oil temp 40 degrees (and also adds some volume to the oil reservoir)