I have been looking at VFDs for my home well pump.
We just recently replaced our pump. The "pump guy" did the job on a
Saturday and, basically, he installed what was on the truck. The "pump
guy" said that "new" pumps don't need the controller (starting unit).
The old pump was a capacitor start (current relay). It worked just fine
for 30 years.
The replacement is just two wire. Since it's about 120' underwater I don't
suspect 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 my
basement. We can hear it from the next floor. There is over 200' of pipe
between the pump and our basement but that noise comes through loud and
2) When it stops it creates quite a bit of water hammer. You can SEE the
pipes move when it shuts off.
From an electrical view it seems to be working OK. Whatever starting
transient it has, it's over is a fraction of a second. It draws just less
than 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 OFF
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 pressure
switch) If it would "work" the pressure switch can just switch the 240 volts
as it does now.
6) Any "programming" would have to survive an indefinite power
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 the
SS frequency/voltage to see if I can cut back the noise within it's
performance envelope. Seems to me that once it's up to speed it might make
sense to drop the voltage a bit to the just above the point where the motor
slows down and the current increases.
I see VFDs with prices below $200. That's my upper limit.
For $700 to $1000 I can have them pull out the well string and put into any
kind of pump I want (including, I suppose, the 3 phase delta, or whatever.)
If I pay to pull a working pump, I will first open up my options. But for
now, I am stuck with the pump that's nearly 200' down and 180' below water.
SO: Has anyone here used these relatively small VFD to "soft start/soft
stop" and otherwise protect an "ordinary" 2 wire induction motor?
Is there a CHEAP one that will do all the above for me?
Are the "cheap" ones basically well made? IOW: will they last about as
long as your basic TV?
- posted 15 years ago