...A PWM drive would be a better choice if you need to slow down the motor a bit. But why would You need to ?
This is long-winded, but you asked so here's your answer.
First of all, thanks to you and valeman for your replies and good info. Now I
know that the motor is running hotter. And why.
To answer your question, it's related to my only other thread on this site earlier this year. My question on that thread was (or became) whether or not pumping with a jet pump causes movement in the pipes and jet body in the well.
I think I now have confirmed the answer that I previously believed to be the answer.
Here's the deal: My well is an older well that was probably drilled in the 40's or earlier. It's a standard 6" well which was drilled at least 70+ feet deep (that's all the rope I had) and the plastic pipes in the well are 60 ft long. So I'm drawing water from 60 ft down.
The problem is that I was told 30 years ago by a well guy who supposedly "knew" this well that "there's only 20 feet of casing in the well."
I take that to mean that there's just one length of casing in the well. I think casing actually came in 22 ft lengths, but whatever.
That conversation was prompted by the failure of the foot valve just after my last ex-wife and I bought this place in 1982. I pulled the pipes out of the well and replaced the foot valve back then and all was fine.
That FV failed last January and I foolishly pulled the pipes out on Jan 12 just prior to the really cold weather setting in. So the pipes were out and I suspect that these freaking plastic pipes developed a bend at the end which is likely causing my problem now.
Which is that if I run my pump normally it pumps like a freaking fire hose. I guess that's causing the jet body down in the well to move around and stir things up, probably banging against the uncased well wall, as a result of which I get sediment in just about all the water I pump. Sometimes it's pretty clear and sometimes it's very brown.
I'm in NJ (the "red clay" State in my area) and the sediment is this reddish-clay/reddish-shale color.
I also am not using any pressure tank. I run the pump with a standard light switch and capture the water in gallon jugs, 5-gallon bucket(s), whatever.
Don't ask.
So, it occurred to me that if the fire-hose pumping is causing the stirring down in the well, perhaps slower, more gentle pumping would help.
And it looks to me (so far) like it has. The water I've pumped so far looks to be sediment free. If not completely sediment free, it's definitely got much less sediment in it.
So that's why I wanted to slow things down when pumping.
Now, granted that this is not a practical solution for a normal human situation, but it works fine for me. Note that I deadheaded the output line (shut the faucet off) and ran the pump wired for 230v and it developed only 12 lbs pressure. When run deadheaded wired properly it goes right up to 60 lbs whereupon the pressure switch shuts the pump off, as expected.
One other thing to note is that I was somewhat surprised that pumping at what appears to be a very gentle rate poses no pumping problem at all. I figured maybe the foot valve might not open and/or the nozzle/venturi combination wouldn't work to actually cause water to pump. But I'm doing it just fine, so I guess maybe I could pump at regular speed with much larger nozzle and venturi orifice(s) than what I have now and what is recommended. In fact, my venturi has a larger orifice (hole, opening, whatever) than is recommended at this depth. Same is true of the nozzle.
The obvious solution is to either have a new well drilled, or have more casing installed (which is probably tantamount to having a new well drilled) or drop enough plastic casing down the well (which is apparently ~5.5" OD, and thus would drop down the well) to make up the difference in the missing area of casing, and thus "case" the well in the area of the jet body. That would probably work. But that casing is pretty expensive and if it didn't work, it would just be wasted money.
The other possible solution is also expensive. That would be to put an in-well pump down there and hope that it wouldn't stir things up to the point that would result in sediment.
But keep in mind that I have that bend in the pipes down there that I don't think was there before, and thus any pump or foot valve might well end up resting against the uncased well wall, and thus suck in sediment any time I'm pumping water.
BTW, my rate of pumping is currently about 16 seconds / gallon. It's nice and slow and gentle. Normal rate is like 4 seconds / gallon.
I just can't believe that the morons who drilled this well didn't put casing in all the way down to the point where they were drawing water. And then some more beyond that.
You can't make this stuff up.