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

 

[TugboatEng]

Permanent magnet excitation eliminates a lot of the issues with regards to harmonics.

 

[LittleInch]

Use Clarification: This is a standby Generator. It will only run when the power is out. In years past, your talking 30-120 hours a year. The location allows fuel to get to it rather easy. Fuel might not be as readily available, in the aftermath of a hurricane. Remember we are located in Florida. Last year our area went without power for a week after the hurricane. We farm and plants need water to survive. No water = Dead plants.

Proper disconnects from power grid are a must. Although we are in Rural Florida, its not the wild wild west, lol. It will be inspected.

Going to build a 100gallon tank, that sits under the generator.

Any issues with Perkins Engines for this build?

I don't think so. For your short term once in a season use it looks good. I would try amd make sure you start it and run it for an hour or two once a month to charge the batteries, make sure the diesel hasn't gone off and you remember how to disconnect the supply.

 

[theplantman]

Ok So we have:

Lionel- 30KVA
Waross- 40 KVA

Attached is the VFD SN# we have installed if that means anything to anyone. The 18A are fans (that run continuous throughout the daylight hours) and are on two breakers, from the panel box. One breaker runs 6 fans, one runs 3 fans.

 

[FacEngrPE]

waross has forgotten more electrical wizardry than I will even know.​

 

[LionelHutz]

Lionel- 30KVA

Forgot to read the rest of the post?

 

[theplantman]

Forgot to read the rest of the post?

No I got you! 30KVA plus the fans. Thanks for your advice!

 

[theplantman]

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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Waross- is the above 40 KVA including the power needed to run the 18amp on the fans? Its seems your opinion comes highly regarded, so I thank you for your help!

 

[theplantman]

WEG or Stamford unit??????? Thoughts on this agricultural, standby application?

 

[TugboatEng]

The electrical ends are all very reliable. I've run Delco, Stamford, Marathon, etc... I've had one hard failure in 1.5 million hours of runtime. It was a high hours unit and very dirty. There was open crankcase ventilation and that really gums things up in the generator. Been through a lot of voltage regulators in that time. I buy better regulators now.

Small sized generators are all essentially open drip proof rated which is about the lowest environmental rating available. They need to be installed in enclosures for outdoor use. Be mindful of the enclosure your supplier provides. Generators are excellent air purifiers and will centrifuge every contaminant out of your air and deposit them on its windings.

 

[waross]

As for those fans. 18A is drawn where exactly? You'll have to add that to the power total.

And if they are n the same phase, double or times root 3.
It depends.

 

[waross]

@waross has forgotten more electrical wizardry than I will even know.​

​

Thank you very much, FacEngrPE

Lionel- 30KVA
Waross- 40 KVA

As your installation is described, Lionel's recommendation is probably quite acceptable.
But, in the event that the VFD fails, 40 KVA is the smallest size that has a chance of starting the pump, Direct On Line until the VFD is repaired or replaced.
And starting the pump DOL may require all other loads to be off until the pump is started.
40 KVA is based on starting the pump at a 2.5 ratio.
That ration is for special cases only.
Normally the minimum ratio is 3:1
Alternately, in the event of a VFD failure, the pump may be wired directly to the generator before the generator is started.
The generator should be PMG excited.
That would not be automatic.
Your choice if you want to spend the extra money to plan for a possible VFD failure.
Many of my customers would have gone with the 30 KVA set.
Some would have opted for the 40 KVA set.
Consider also possible future expansions and possibly a larger pump.
.

 

[waross]

A disclaimer:
I would not size this set for a customer without more data and without verifying the data given.
Set ratings: If the set is rated for 30 KVA at 120/208 volts, it may be dialed up to 230 Volts and the KVA will increase to 33 KVA.
230 Volts has not been a standard North American voltage for decades.
The standard 240 Volts is still sometimes referred to as 220 Volts or 230 Volts. The actual voltage should be verified.

 

[XR250]

At my old house, we had a 1 HP, 240V well pump and it would bring my 9HP generator to its knees on startup.

 

[EdStainless]

Well motors draw significant start current.
Between the poor motor geometry (longer and smaller diameter than usual) and the length of cable it can be a real issue starting them.
Double checking actual voltages is very critical.

 

[LittleInch]

At my old house, we had a 1 HP, 240V well pump and it would bring my 9HP generator to its knees on startup.

Also depends on other loads or no load.

Prob better to have some load on the generator then switch them off just as you press start on the pump.

 

[waross]

At my old house, we had a 1 HP, 240V well pump and it would bring my 9HP generator to its knees on startup

If the pump is the only load, it is probably an issue of the Genny struggling to pick up load from high idle than an overload issue.
Your engine is at high idle.
The load hits.
The engine must drop revs before the governor reacts.
At minimum fuel flow, the revs will drop a lot and the engine my be expected to struggle to recover.
Try a connecting a 1000 Watt load and then start the pump, with the 1000 Watts still on-line.
While the starting current may be 600% or more, the starting Watts may be 300% more or less.
There are a couple of factors involved when starting a motor on a relatively small gen-set, both on the motor side and the gen-set side, that are overlooked when starting DOL on the grid.
300% Watts versus 600% KVA is one overlooked factor.
UFRO is another factor with most gen-sets.

 

[XR250]

Def. was not much load on the genny prior to the pump kicking on - usually just lighting. The other things it did not like were my HP4000 laser printer and a microwave.

 

[theplantman]

A disclaimer:
I would not size this set for a customer without more data and without verifying the data given.
Set ratings: If the set is rated for 30 KVA at 120/208 volts, it may be dialed up to 230 Volts and the KVA will increase to 33 KVA.
230 Volts has not been a standard North American voltage for decades.
The standard 240 Volts is still sometimes referred to as 220 Volts or 230 Volts. The actual voltage should be verified.

Waross- I think what we have here is 240volts, but the folks keep calling it 230v. Our generator built is going to be a 50KVA generator. That sounds like it has enough power to run everything and/or/when the VFD fails, it can still DOL the pump to start.

Thanks for all your advice!!

Alex the Farmer