Questions on Single Phase VFD for well pump

John Gilmer · 2006-06-29T02:56:42+00:00

Hi:I have been looking at VFDs for my home well pump.We just recently replaced our pump. The "pump guy" did the job on aSaturday and, basically, he installed what was on the truck. The "pumpguy" said that "new" pumps don't need the controller (starting unit).The old pump was a capacitor start (current relay). It worked just finefor 30 years.The replacement is just two wire. Since it's about 120' underwater I don'tsuspect it has any moving parts other than the rotor itself.The new pump has two problems I didn't see with the old pump:1) When it runs it transmits quite a bit of 60Hz "hum" back to mybasement. We can hear it from the next floor. There is over 200' of pipebetween the pump and our basement but that noise comes through loud andclear!2) When it stops it creates quite a bit of water hammer. You can SEE thepipes move when it shuts off.From an electrical view it seems to be working OK. Whatever startingtransient it has, it's over is a fraction of a second. It draws just lessthan 10 amp at start and increases to just below 11 amps at shut off.I would like a CHEAP package that would:1) Start the pump a little slower taking about 1 second to ramp up.2) On stop, take about one second to slow down.3) Offer protection from "short cycling" with a two minute minimum OFFtime.4) When running in the steady state, it would operate the motor at specs(60 Hz, 240 volts).5) On/Off would be controlled by contact closure (2 pole pressureswitch) If it would "work" the pressure switch can just switch the 240 voltsas it does now.6) Any "programming" would have to survive an indefinite poweroutage.Because of point #4, I don't expect any VFD to change the amount of "hum"making its way back to the tank. I suppose I might "play around" with theSS frequency/voltage to see if I can cut back the noise within it'sperformance envelope. Seems to me that once it's up to speed it might makesense to drop the voltage a bit to the just above the...

Jun 29, 2006 21 Replies

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John Gilmer 19 years ago

Your reply is worth the wait!

No modification. The failed unit had the control box with the capacitor and the current sensing relay.

The replacement unit was just 2-wire.

So you are saying that there is some kind of switch build into the pump that's sitting in the lubricating oil? Do they have a capacitor down there too?

Well, the pump only has a 5 year guarantee. With all that stuff down there waiting to fail I doubt that I will get 30 years of service out of it.

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John Gilmer 19 years ago

I check our your URLs.

"They" put a lot of stuff down there. I don't know if my model has it, but some of those motors, it seems, will detect if they are jammed with sand and run backwards to try to clear things out!

Simply amazing!

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