Depth of water sensing 1

[alternety]

I would like to monitor the water depth in well. Maximum depth is 500" and minimum is 0'.

I have been thinking pressure sensor but everything I have found is quite expensive packaged sensors.

Any ideas on other ways to monitor depth or sources of something I can use for a sensor in a 500' well.

 

[Warpspeed]

Try to imagine if the well fills to within one inch of the top of the well casing, almost no work needs to be done to get massive flow.

If the well is pumped almost down to the 600 foot level, water need to be forced up through every one of those six hundred feet.

What actually happens depends on the type of pump, but the actual drive power requirement will change rather a lot I would expect.

 

[Skogsgurra]

I think that it is all very easy (if we can forget about the stuck things - I know, not easy to forget).

Motor current is not a good measure of water level, but motor power is. Power can be measured quite easily with a kW/current loop converter, which is a standard device and not very expensive.

Depending on pump curve, the flow goes back more or less when head increases. But a situation where flow times head (i.e. power) stays constant is not likely. The problem is that one has to measure a rather tiny change on top of a high power level. So secondary effects like mains voltage fluctuations and water temperature may disturb the measurements more than one can accept.

But, with a sufficiently fast measurement, it should be possible to indicate dry running and turn the motor off very quickly (40 - 50 milliseconds). Dry running will dramatically lower the power taken by the motor and it will be a very reliable indicator. Since dry running doesn't happen instantly, but gradually, and probably never with a completely dry pump (water will fall back into the pump and "grease" it because of bad pumping action and high water head) you will have the best of many worlds: reliable level indication, nothing to put down the hole, no risk of dry running the motor, level sensing always on same level as motor. You will also have a good indicator of water level since pump power can be read from the 4-20 mA signal and there is a corresponance (probably not completely linear, but monotonic) between head and power.

I will remeber your stuck sensor in my prayers.


Gunnar Englund

http://www.gke.org

 

[Warpspeed]

Yeah, one beady eye focused on the amp meter, and the other beady eye focused on the flowmeter, and do some tests at midnight during the next full moon.

 

[alternety]

It was still stuck when I left last night. I did run the pump, I need some water, but the type of pump it is has almost no vibration and there is no starting twist. It has controlled power ramp-up (i.e., soft start).

It is a positive displacement pump. It is a steel screw in a rubber casing. There is a check valve above the pump. Water won't run back. The bearings and pump all use water to lubricate.

Current is a reasonable indicator and I have some curves from the manufacturer. The controler holds the 32 VAC three phase fairly constant and the curent varies if I remember correctly. I was going to monitor this eventually ((after I live there). I wanted an independent sensor that can read while the pump is not running to see rate of recharge.

 

[alternety]

The well is healed. The secret was the sacrifice of a small mammal behind the well head at midnight.

Here is what really happened. The probe is still stuck and will be abandoned in place. I talked to the pump manufacturer again and tech support said there were many of these controlers that work OK with the old probe. Told me what wires to attach. I told him that that is the way I did it before. So, just for jollies I reconnected the old sensor. Did not work.

I put a meter on the probe terminals to see what the voltage looked like and it was strange. Reversed my probes and the voltage changed. There was some AC on the line. Thought - ground current; but from where.

When I initially installed the system a couple of years ago with the old controller it would trip the GFI breaker whenever it turned on. I fixed this by isolating utility ground from the system ground at the power supply. That fixed it. FIgured I would do it the right way at final install where a GFI would not be required.

Today I poked around with the meter trying to find the source and saw a noticable potential between the two grounds. Connected the chassis ground back to the utility ground and presto - it works. I just spent about $350 and many hours I do not have to spare trying to replace the sensor when all it needed was that wire.

@&@)(&@$&@%)@!_+_)%$#(*&&*#

I will address the depth sensing at a later time. I have really appreciated the thoughts and ideas you guys have contributed here. It has been incredibly helpful.

 

[Warpspeed]

Very relieved to hear things are finally going your way.

 

[itsmoked]

No permit shall be issued unless and until the following water source requirements are established as prescribed in Section 7.73.060:

B. August through October. For each connection to a well water source, a minimum of two gallons per minute of yield must be sustained during a twenty-four hour period of continuous pumping, or until two thousand eight hundred eighty gallons have been achieved during a time period of twenty-four hours or less of continuous pumping.

So your 2 gallons/minute doesn't sound to bad to me.

 

[alternety]

3 actually. I have almost a gusher.

 

[Yashu]

Can't it just be simple...

put a 'water sensor' at a low mark location... and another at a high mark location...

if water get's to the hi mark... pump out well until low mark...

bottom of well water detector provides a failsafe for the pump

KISS

 

[itsmoked]

Yashu this well is 500 feet deep with the pump already installed. NOTHING IS EASY about it.

 

[Skogsgurra]

"the sacrifice of a small mammal behind the well head at midnight"

Not the cat, I hope?

Gunnar Englund

http://www.gke.org

 

[ScottyUK]

I can offer a suitable cat if required. I'm sure my wife won't notice...


----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[VEBill]

My 300-foot deep drilled well is simply equipped with the usual $30 pressure switch - the sort the turns the pump on when the pressure drops to 30 PSI and turns the pump off when the pressure reaches 50 PSI.

Safety feature: If by chance the well is pumped dry (two hoses plus several hours, maybe...), then when the pressure drops below about 15 PSI then the switch turns off totally and must be manually reset.

I didn't think that anything more complicated than that was 'required'. I understand that it would be 'interesting' to track the depth of the water in the well - interesting like watching paint dry after about the first week.

2 or 3 gallons a minute is around 3,600 +/- gallons a day. That amount is probably almost enough for a laundromat (but not quite). Get a big pressure tank to reduce pump cycle and make it easier for your well to have time to recover.

We should rename this thread to 'Depth of Message Thread Sensing'.

By the way - calculate the pressure in the pipe near the pump (at 500 feet down?) when the water level drops to almost that level (this is the worst case). Compare this pressure to the pressure rating of the pipe. It can be amusing.

 

[itsmoked]

Amusing? Like when our fire crew layed 1.3 miles of fire hose that ran down slope 1,500+ feet?

93! posts must be some sort of record!!

 

[alternety]

94

I realize this thread has too many posts to keep the objective in focus. Brief summary:

Two problems.

1 - Track water level to determine how the well is performing. Track recharge rate and static level. Unproven well capacity. That is what most of the discussion is about.

2 - Protect the pump from running dry. This pump can not be protected by sensing dry running after the fact. Everything is water lubricated. No water = no pump.

Other - pressure is around 200 PSI. Pipe is fine. Lava would upset the whole thing.

 

[VEBill]

There are millions of drilled well pumps using nothing more complicated than the normal 30/50 PSI pressure switch that I've already described (with the ~15 PSI cut-off).

Nobody (at least virtually nobody) is using water depth info to control their drilled well pump. This thread clearly demonstrates why nobody is doing so...

In my case, for various reasons having to do with freshening up the water quallity once in a while (over about 16 years or so), I've purposely emptied my 300' drilled well many times. Several times per year x 16-odd years = about 50-ish. Never a problem (knock on wood).

The pump doesn't really run dry. It starts sucking air while sloshing around in the last remaining inches of water. As soon as it does so, the pressure switch at the top end will shut it down within mere seconds. Then within a few more seconds it will be submerged again (2 or 3 gallons a minutes coming in, takes less than a minute to submerge it again).

Obviously, surviving the inevitable dry well must be a fundamental performance and reliability requirement for the pump designer.

I expect that most pumps die of old age (something corrodes or cracks due to age or exposure to the environment) long before some occasional mild abuse would do them in.

There must be a half-dozen guys (engineers, technicians) at work that are interested in knowing their well depth. Not one has ever implemented anything.

It would be a big market...

 

[VEBill]

500 feet is (as you wrote) about 230 PSI. That depth and pressure is slightly beyond the normal. Hopefully your well installer has selected the appropriate spec'd pipe.

One of my well pump bidders (many years ago) specified 100 PSI pipe for my 300 foot well (up to 144 PSI). He also specified wire that would have had too much voltage drop. He didn't get the job.

This reminds me of a joke - if you're lost in the woods in Canada, then simply pick up a chainsaw, axe, or hachet and start cutting down a tree. Within seconds, some plaid-clad lumberjack type will appear from nowhere to show you what you're doing wrong.

If you're lost at sea, just start to tie a knot in a rope. That's it - instant rescue. Within seconds, "No no no no, that's not the right type of knot..."

I guess wells are the same thing.

PS - If you're lost in the Phillipine jungle, then you put your underwear on your head. Within seconds, "Hey Joe, you know that your underwear is on your head?"

 

[itsmoked]

97! Who w i l l b e 1 0 0 ?

1) Unless you are a well, hobbyist, addict (like I might admit to), as VE1BLL correctly points out: caring about the wells performance/recharge rate will be as exciting as watching grass grow or more directly; a puddle evaporate. You will find out the well performance/capability soon enough and it will be fine or you will need to make changes(no baths on alternate months).

Frankly if you are running a tank as is required most everywhere, for how else do you provide the 1,500 gallons of fire fighting water most places demand, then it will be no problem to keep that thing full unless a dairy is involved. You are providing a tank? Tell me you have a tank. A nice 2,000 gallon one... Or two.. The guy next to me put in two 5,000 tanks side by side to support his private one person observatory bathroom, (the only thing on the site.

2) You can easily see if the pump is going dry by watching the discharge pressure. I don't care if that pump is made out of pumice spinning in cotton bearings, it's not going to lunch itself in 1.00 seconds while it starts to suck a little air/water mix. You are being overly paranoid. Yes you would not want it to go on and on nor occur at the end of every pump cycle but a few calibration gurgles is not a problem. If you are convinced it is a problem then you must buy the $1,115 plus submersible sensor noted above and some electronics and monitor the well performance and turn off the pump too while your at it.

As I continue to beat this horse,(now into a red pulpy goo), Here's-what-I-would-do:

1) Put up a storage tank if you don't have one. This drops the panic factor when working on the well as you have a few days of reserve on hand.

2) Put up a storage tank as this is much better for the down hole pump to not cycle constantly. It also allows a current or flow monitoring if desired.

3) Run the down hole pump with a float switch.

4) Run a second three phase pump with a VFD (single phase input) into a small pressure tank. Use pressure sensor feedback to exactly control this three phase pump to maintain the perfect house pressure. No on/off, on/off, garbage when some faucet-garden hose combination causes maximum pump cycling.

And spend, spend, spend as it's all justifiable. One must have a nice well after all.

 

[Warpspeed]

Without actually knowing for sure, I would guess that the pump itself would probably have some sort of float switch that would shut off the juice before the water level fell below the pump intake or motor/bearings.

It is probably a fairly simple, reliable fail safe system, otherwise the pump manufacturer would most likely have been sued into bankruptcy a very long time ago.

If you can plot motor current, or well flow, versus water depth, that could then be used to automate pump cycling without relying on the safety cut out.

 

[alternety]

Guys, you are debating this with the wrong person. I am paranoid, but not specifically about the pump. This is not your father's pump that you and your neighbors have used for however many years.

The pump uses a steel on rubber interface that tends to melt fairly quickly without lubricant (i.e., water), and lock the rotor. It is not a centrifigual or piston pump.

The pump motor uses fluid bearings. The fluid is ,wait for it, water. How long do fluid bearings work without fluid - a minute or so? I don't know, but I suspect not. Nor do I wish to collect experimental data.

The pump manufacturer specifies, and supplies, a protection device so that the pump will never ever pump dry. This device is installed.

The warranty is void if damage occurs to the pump because of dry pumping.

Please drop this aspect. It is unproductive. You want to argue - buy one and experiment.

The tracking. Yes I can do a number of things. We are going to be doing a lot of gardening. We have 5 acres. The well is in solid rock with unknown sources of water. There are no alternate water sources. A shallow well on the property goes dry in the summer (shallow meaning it goes to bedrock). There are drought conditions that come and go. Salt water infusion is an issue here.

The configuration - well pump (about 32V 3 phase AC), low water protection sensor. This pump will be controlled by a float switch in a 1500 gallon storage tank. Storage tank feeds a 1.5 HP DC variable speed pump (25 GPM max) that pressurizes the house system. This pump will be protected by a float valve in the storage tank (it is a multi-stage centrifigal, but the manufacturer does not look favorably on dry running either) and controlled by the normal system pressure switch. Bladder pressure tanks and a 0.04 micron water filter complete the system. Well, an RO unit to take arsenic out of the drinking water is also included.

Believe me - I would not be doing anything I did not consider (based on manufacturer recommendations/requirements) necessary. It costs money, grief, and time I do not have. Please put these issues to rest.