Sizing Generator- Florida Nursery

[theplantman]

We have recently installed a new 20hp well that runs some critical watering areas on our farm. We want to have a standby generator installed, and in reaching out to generator/electrical companies, we are getting many different opinions on what we need. As a result, I have landed here to ask for advice. Here is what we have that we want to run, and the equipment that has been installed thus far:

Duke Energy 230 3-phrase power (I am told this is the highest we have available)
Pump Motor: Franklin 20hp pump model #236604 Franklin Motor Link (see three attaches pages on this motor)
Danfoss VLT AQUA Drive FC-202P18KT2ERH (see photo)
(18) Greenhouse Fans. They draw 1amp each, wired 110v.
(6) Very small irrigation timers.

The most complete quote, was a custom Diesel Generator made for this application. See attached quote.

We have gotten proposals from companies for 30kw, 40kw, 65kw with either Propane or Diesel. The issue is no consistency or agreement between electricians we have reached out to, so makes us worry about selecting a company/generator and it be to small and not work, or way overkill and burn up unneeded fuel. If there are any questions or further information I need to gather, let me know!

Thanks!

Alex the farmer

 

[waross]

Duke Energy 230 3-phrase power (I am told this is the highest we have available)
????
I thought that 230 3-phrase power died with the Dodo.
Do you have a niche open delta wild leg service?
Some guesses based on incomplete information:
Simple calculation based on 120/208 V service. 30 KVA.
Based on 230 V, wild leg service, 40 KVA.
Pump on DOL, 65 KVA.












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[TugboatEng]

In that size range, if you go diesel, I think you'll find that the 65kW unit burns less fuel at all power levels the smaller units are capable of producing.

Pricing is going to vary wildly.

 

[theplantman]

Yes we have 230 3-phrase power on our farm. We are way out in the country and thats the strongest power available out here. What other information do you need Waross?

There are only 2 transformers on the power pole, and the well man says we have "niche open delta wild leg" service. He called it "open delta" power.

 

[TugboatEng]

It has nothing to do with your problem it's just interesting to note that some voltages are not so common anymore and the difference will have little effect on your system. I have had boats in my fleet set up to run on 440, 450, 460, and 480 volts. When we plug into shore power I get 495V. Everything still works fine except the consumer grade UPS's sometimes had to be replaced with industrial units. I re-tapped transformers where I could. The 450v is a typical problem I run in to with marine electricians. If nominal is 110-115 then 112.5 is perfect! Also, DC wiring needs to be at least 10x larger than AC wiring of the same ampacity.

You'll be able to fudge the specific numbers with your voltage regulator. Give yourself some fudge room on the nameplate rating if you're going to be operating at a lower voltage.

 

[waross]

You'll be able to fudge the specific numbers with your voltage regulator. Give yourself some fudge room on the nameplate rating if you're going to be operating at a lower voltage.

BE VERY CAREFUL FUDGING.
More than once I have spec'ed a standby set very close for a known load.
I spec'ed but didn't order nor did I have a chance to vet the order before shipping.
Ordered was a specific KVA at 120/208.
Shipped was the spec'ed KVA but at 120/240 wild leg.
So now I have a set that is 208/240 = 87% of the intended load.
No problem right? Just send it back to the supplier and have it replaced with the set as ordered.
When the supplier is an ocean voyage away, that is not an option.
Not even discussed.
You live with what you got.
I had to come up with a creative automatic load shedding scheme when the standby kicked in and live with an unhappy customer.
Yes, I could have solved the problem with a transformer bank but cost was an issue.
I did negotiate a discount for both customers but that didn't completely cure the pain.
With as installed onboard sets and lots of shore power, tweaking is fine
I have often done that myself when I had a lot of marine work.
But, when sizing a new set, there is no room for tweaking.
Do it right and get it right.
If possible vet the order before it is shipped.