ECN Forum Forums General Topics of the Trade General Discussion Area 3 phase well pump

Larry, I bet it is a PVC well casing.

Reno, If he doesn't need a lot of flow, it doesn't have to be that big a motor. He sounds like he just wants to keep a stock tank full, not water a golf course.
If this is one of those Las Curces dairies I retract my statement.

My estimate is that at [say] 80% efficiency, that is allowing for throttling and other losses, a good pump design should be capable of 3Wh/[US]gallon. 3HP would thus give about 2000 gallons an hour. Cows drink/use a lot of water though, next door reckons on at least [converted] 33 gallons a day each. Ergo, 66.66 cows!

I don't see that single phase v 3phase makes much difference to efficiency, the amps in a 3 phase set up are less because of the [usually] lower current carried in each conductor and a 3 ph motor is slightly more efficient electrically. Besides, even at 120v single ph, 3hp only comes to 25A by my reckoning.

As to torque, I suspended my well pump on a thin stainless steel multistrand cable to avoid lifting it out by the power cable.
It's a 1.5hp 4-stage axial turbine type, 230v single phase run at about 25 feet depth at 45psi gauge. Any torque twist on startup is very momentary [just a twitch] and of quite small magnitude, and imho not worth worrying about. I have run this pump free standing in a butt, to test it, with nil twist problems.

Alan

Math correction, Units: That should have read 66 and 2/3 cows per hour, of course.

All the well casings I've ever come across are steel and the lengths are butt-welded as they are sent down the well as it is drilled.

I fail to see how a well-casing if metallic, instantly becomes a risk during lightning episodes, it is of course underground.

The 4 inch or smaller wells are threaded tight when they drive it down { the 4 inch can be either welded or threaded one of the two }

The larger one no question asked automatic butt welding.

The deepest well I ran into with sumbersble verison that go little over 300 meters ( 900+ FT } that have 40 HP motor on it. the supply pipe is 4 inch rigid pipe bezjezz that sonvagunner is very hevey.

One thing I know the code is oversighted on this one they should done in first place get correct bonding conductor that will really elemated all the ground rod issue there.

Merci,Marc

I guess I am just confused about how much head you need on those wells. Around here the wells are typically around 200 feet but they have a static water level from -13 feet in the spring (dry season) to bubbling out of the ground.
We all had shallow well (surface) pumps until the yankees came down and started watering the grass. Sometime when they all turn their sprinklers on at the same time they pull down the static water level so low a shallow well pump will cavitate.
The casings are always bell end PVC that they just glue together as it goes in.

"I fail to see how a well-casing if metallic, instantly becomes a risk during lightning episodes, it is of course underground."

My point is when you bond the electrical system to the well casing, you provide an excellent ground rod. Would this make the electrical system MORE attractive to lightning?

Larry C

Larry: Found this:

http://www.inspect-ny.com/water/WaterWellLife.htm

Last paragraph:

"..Water pump wiring especially for submersible pumps, and the pumps themselves are vulnerable to damage from lightning strikes. It's possible that the combination of electrical wiring and the steel well casing are attractive to lightning, particularly when the well casing extends above ground level (as is common practice with modern drilled wells). Electrical surge and lightning protection systems are available for installation (usually at the electrical panel) to reduce the risk of well wiring or pump damage from lightning.

What does Carrot Top have to say about it?

Inspect-NY seems to be a pretty dubious source. They deal in a lot of conjecture and anecdotal "evidence". Their main objective is printing out home inspection reports that discount the selling prices of houses. Have you ever read their "aluminum wire' tirade. It is basically "run for your lives, it is gonna blow!".

I would say that if you have decent bonding practices the well pump is no more likely to be damaged than anything else. I live in a place with a butt kicking thunderstorm almost every afternoon in the summer and I don't hear stories about a lot of blown up well pumps. We all have wells.

Apologies Greg/all for the dubious link. Ignorance is bliss! Thanks to Google, I was able to find out a bit about Carrot Top and his zany inventions. His take would probably be to put some wheels on the well so you could tow it away in bad weather.