3 phase at 208 or single phase 240 on a genset

[mr.shiva]

I recently purchased a diesel gen (cause pg&e is a rip!) and I'm getting ready to wire things up. My gen is setup 3 phase 120/208 at power factor of .8 , if I setup single phase it has a power factor 1.

Am I correct in believing I'm getting more bang for the buck at a power factor of 1 ?

 

[rives]

I recently purchased a diesel gen (cause pg&e is a rip!) and I'm getting ready to wire things up. My gen is setup 3 phase 120/208 at power factor of .8 , if I setup single phase it has a power factor 1.

Am I correct in believing I'm getting more bang for the buck at a power factor of 1 ?

Assuming that you can load all three phases evenly, then the answer is no. This gets fairly complicated, so I'll quote from the attached link. Basically, you get a substantial savings from running 3-phase, that's why industry uses it.

"In order to calculate three-phase wattage, we multiply the average voltage of each phase times the average current of each phase, times the power factor, then multiply by the square root of 3. The square root of 3 is equal to 1.732, so the equation is written as shown:Watt's Law: W = V avg. x A avg x p.f. x 1.732"

So if you have 3 ballasts drawing 2 amps each connected evenly across 3 phases, you will draw 4 amps on each phase (each phase feeds 2 ballasts). So, 208v x 4a x .8 x 1.732 = 1152.8 watts.

The same 3 ballasts, connected on single phase will draw 6 amps per phase (we will assume that the higher voltage on single phase is still 208, it gets worse at 240). This gives you 208v x 6a x 1 = 1248 watts.

http://epb.apogee.net/foe/frwt.asp

 

[mr.shiva]

3 phase at 208 or single phase 240 on a genset

Thank you Rives, 3 phase it is

 

[mr.shiva]

3 phase at 208 or single phase 240 on a genset

Looks like 110/208 panels aren't too different to wire. Going to special order some 208v mag ballasts.

 

[rives]

I'd be interested in how this works out for you. I've always thought that diesel generators would be far too expensive for full time use, even with PG&E's usurious rates. I have one for back-up power and by the time you factor in maintenance, it is a damn expensive way to make power. Of course, we also enjoy about the highest fuel costs in California.

 

[mr.shiva]

It's with great intrepidation I give the generator a go. I'll let you know how my luck turns out with this ... From a venture capitalist standpoint the diesel gen sounds really good on paper, quite a few more lights for the monthly fuel cost.

I'm looking forward to getting busy with the wiring

 

[OhighO]

Phasing issues aside. How are you containing the noise from the generator?

 

[mr.shiva]

it's a mq power whisperwatt, noise is 60 dba full load at 23ft. Sounds like your standing next to a truck idling. If it was any quieter I'd be tempted to fire one up in town.

deapsea controlers -- peak shaving, grid syncing ... looks pretty interesting to me if I had a backup generator hooked up to my house on the grid.