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.

 

[itsmoked]

100! BOO_YAH!

 

[itsmoked]

Well, oh....kay... sheesh.

Sounds like a nice system overall. About what I'd do. I thought 32V 3-phase was just some sort of psychotic spasm of the pen by a paranoid... but you keep doing it, which makes me start to believe it. Why is it 32V? Are you off the grid?

What brand is it? I'd like to read about it.

 

[alternety]

The system is actually designed to run from 48 VDC solar panels. I built a DC power supply to replace the panels. The reason for using the pump is power consumption and robust design. The most I have measured as pump input is about 500W. This is not exhaustive monitoring but anecdotal.

The pump is made by Lorentz in Germany. Importer is

http://www.conergy.us/DesktopDefault.aspx.

It was the most interesting and energy efficient pump I could find. Have fun. You should see my heating system .

 

[itsmoked]

Hahah heating.. probably needs water? DOH!

Thanks for info. Next question: What state are u in?

Hey did you see this Circuit Cellar contest winner?

http://www.circuitcellar.com/psoc2004/winners/c2982.htm

It said solar and three-phase. I scratched my head but I bet it's for one of your pumps after realizing the low volatage.

 

[Skogsgurra]

Hold it!

Someone is pulling a lot of legs here.

I do not accuse you, alternety. But I do question your sanity.

A motor cable being 500 ft is bad news even if you were using a higher voltage. With 32 V it should be a catastrophe with voltage drops in the 50 percent range if you do not use a cable as thick as an arm (and a leg - I would like to add). What gauge is you cable? No wonder things get stuck in the bore.

Otherwise, this has been a very fun and instructive thread that we can learn a lot from. It has also produced some very good little essays that, no doubt, will be engineering classics in the future.

Now, who will post #200?

Gunnar Englund

http://www.gke.org

 

[Warpspeed]

Hmmm,

500 watts at 32 volts is 15.625 amps total. Distributed over three phases is only five and a bit amps per phase. That is not a huge amount of current.

Let's allow for 5% resistive cable loss (15% total) in each phase at 5.2 amps, that is a voltage drop of around 1.6 volts per leg. Maybe 0.3 ohms per phase at full load.

Suppose we specified 10mm squared capacity cable (nominal 50 amp rating) that would allow for a cale length of around 174 metres. Rather more copper than that would be desirable, but I just wanted to get a feel for the figures.

If the motor power unit had remote voltage sensing, it would be theoretically possible to fully compensate for any reasonable voltage drop by automatically increasing the source voltage at the three phase inverter. Certainly possible, and if I was designing a deep well pump power supply that is probably how I would do it.

Engineering can be fun. Was it a black cat ?

 

[VEBill]

A 500-watt pump for a 500-foot well? - geesh. Why bother saving power on something that should have an ON duty cycle of much less than 1%. If you're on the grid, then you've spent a lot of extra money to save maybe $5 per year.

32-volt 3-phase? WHAT? 'Oh one more thing I forgot to mention is that the well is on Mars where the gravity is slightly lower.' ;-)

Personally, I've got to get back to monitoring the cathode voltage on my TV set. Everyone needs a hobby...

 

[alternety]

I am in Washington on an island about halfway between Seattle and Canada.

Yes the heating needs water. The system has been sitting waiting to get filled for many months until I could find a way to get rid of the suspended solids in the well (the pump and assorted things I have put down there are not considered suspended solids).

The wire is #6 copper.

One aspect of the pump is that is does not have huge turn-on spikes. It is soft start. This makes it easier (read cheaper) to configure a backup generator for the house. It also lessens the possibility of breaking the PVC pipe from starting torque. Such things happen with centrifigual pumps. Except for needing water, it is also a quite robust system and should yield good equipment life. This type of pump head design is I believe used in things like oil wells with dirty materials.

I saw that Circuit Cellar article and had the same thought. The circuit board does not look quite the same as the one in my controller and I don't know who actaully makes the controller. The CC design appears to be for a higher motor voltage. That would make the wire much less of a factor. I really don't know why my controller was designed for low motor voltage. Possibly a mind set about solar power being low voltage. Maybe component issues when they first made these things and they stuck with it for backward compatability to the pump motors in the ground. The guys selling the pump do not have any info on the internal circuits. Their vendor considers them proprietary.

With a lot of plants to water the pump will probably run a good bit. Compare the pumping efficiency and power consumption with the 1-2 HP centrifigual pumps that would be the alternative. And some of the better ones of those actually put the electronics down the hole in the pump body. That feels way dumb.

My wife has also been known to have some nagging questions about my sanity. But she appreciates having a pet engineer on duty anyway.

Black is traditional. Calico yields spotty results.

If it will be of any assistance, the way I usually monitor my monitors is to add a custom coil to the neck of the CRT. I have a detector focused on the screen with video analysis software that can track and measure an individual video dot. By using a half frame every so often with a known magnetic field applied I can calculate the anode voltage from the deflection distance of the electron beam. It is fast enough that a normal viewer does not see the stolen field.

 

[itsmoked]

alternety you and your well are a classic.

On my next yacht delivery I'll drop by.

 

[Skogsgurra]

Even with 100 percent efficiency and no friction in the tubing (working against static head only) a modest flow rate of 1 litre/second would demand about 1500 W shaft power and that would be something like 27 A at PF=1 and 34 A at PF=0.8

A #6 wire has abt 13 mm2 area and will have a voltage drop of around 6.7 V/phase or 11.6 V measured between phases.

I have never seen a pump with 100 percent efficiency, so either you have measured when the water level was quite high - or you have a flow much less than 1 l/sec. What does the nameplate of the pump motor say?

You have proven adequate sanity by telling us how to monitor electron flow in your CRT. Much appreciated. Sanity will not be questioned again. We are moving towards 200. Like it or not.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

skogs... back in the olden days, (Post 7 of this script),
the dear,(paranoid), alternety stated 2 gallons per MINUTE.

Yes I blew right by that for the next 70 posts thinking 2 gallons per SECOND!

2 gallons per minute equals 0.126L per second. Near the proverbial "kidney rate".

I get 0.45Hp for the expected flow/head which matches rather well with 500W.

 

[Skogsgurra]

I was searching for flow information somewhere. But - as usual - I didn't see it when I was looking at it. OK, 500 W makes sense for 2 gallons/minute. I think...

There will probably still be enough controversial stuff in this thread to keep it going to 200 and beyond. Like dividing by three to get current in a three phase system. Or the ability of a PVC tubing to withstand about 200 PSI. Or if it is OK to steal your wife's cat to sacrifice behind the well-head. And much more.

Gunnar Englund

http://www.gke.org

 

[Warpspeed]

I can see some logic in employing a three phase induction motor. It is the simplest system providing sufficient starting torque without requiring start/run capacitors or switched start windings. You can just pot the entire motor winding and entry cable, and it would then be a solid impervious lump.

The cylindrical rotor would then run wet inside the potted stator, a lovely simple reliable arrangement.

Three phase is also an efficient way of transferring power over lengthy cables, which is one reason it is used for the power grid instead of single phase.

Thinking about it, extremely fine wire in the motor windings and a very large number of turns may not be as reliable as fewer turns of much more robust wire. So for the ultimate in reliability a lower operating voltage may be a good thing. The only real down side is the once only cost of the supply feeder cable.

I would expect if motor efficiency were compared to cable transmission loss, the overall losses would be well balanced between the two. Sounds like a pretty good well thought out system to me.

 

[Warpspeed]

skogs, my calculations were intended only as a very rough grossly oversimplified ball park estimate to get some sort of a handle on cable requirements.

Motor power is given in watts, not in volt/amps as it really should be for a reactive ac circuit. It was easier to just assume the current split three ways and accept that as the rather suspect basis. There is really insufficient information available to do it properly.

 

[itsmoked]

Okay... Are we thru here? Is there anything else alternety wants to discuss? Are there any questions pending? I hate to see this thread go... it has become like, an, old friend.

Perhaps we should start critiquing the heating system? (Which should have R.O. water and antifreeze mix in it!)

In closing I will present a runner up in the 24th annual San Jose State University Fiction Contest which highlights the literary achievement of 'most terrible sentences that take their inspiration from the writer Edward George Earl Bulwer-Lytton who started a novel with "It was a dark and stormy night."'

Ken Aclins, Grand Panjandrum Award:

"India that hangs like a wet washcloth from the towel rack of Asia, presented itself to Tex as he landed in Delhi (or was it Bombay?), as if it mattered because Tex finally had an idea to make his mark and fortune and that idea was a chain of steak houses to serve the millions and he wondered, as he deplaned down the steep, shiny, steel steps, why no one had thought of it before,"

 

[Warpspeed]

The heating system is of vital significance and definitely requires in depth discussion and full engineering analysis and evaluation by this august Forum.

So fess up alternatey, what gives with the heating system ?

 

[alternety]

Do we really want to do this? It gets us further into the building project from Hell.

 

[itsmoked]

hahahaLOLOLololol. Let me wipe my eyes. <sniff>

Only if you want alternety... There are some bright people around here if you want a critique or suggestions.

I was a technical analyst for the California Passive Solar Home Design contest. We saw some real doozys.

 

[Skogsgurra]

118 - and counting...

Gunnar Englund

http://www.gke.org

 

[alternety]

If there is anyone out there still waiting with bated breath to hear about the heating system; your reward is ready.

I am reopening this thread to see if the same guys are still monitoring. The previous exchanges were both helpful and entertaining.

There is a problem. For those of you supprised by this - there is a cloud of bad Karma surrounding me that makes my entire personal warped space a subset of Murphy's laws which, of course, underpin all known engineering principles.

The house has exposed concrete floors with embedded heatng tubes. There are a large number of zones. The reasons for the numnber of zones include personal living preferences, normally unused/unheated space, radically different loads (e.g., greenhouse, room with serious Southern glass). The basement has fewer zones. Upstairs (primary living space) has a floor with the following construction. Subfloor, 3" foam, 2" regular concrete. Each zone has a thermal break between adjacent zones.

The boiler is a condensing 85K BTU variable firing rate unit. There are about a half dozen controllers taking care of things. Solar exposed slabs have embedded temperature sensors. DHW (domestic hot water) is indirect and uses a well insulated tank heated by boiler water in a coil. There is another tank in the system that acts as a buffer for the heating loops to prevent short cycling of the boiler when a small demand is made (e.g., one bathroom). There is a dedicated loop to heat make-up air for the range hood. This loop is controlled by a variable speed pump that senses temperature drop across the coil.

Now we get to the problem part. Did you get a fresh beer? The "normal" way to pump the heating loops is to run a fairly large pump at full speed and provide a pressure bypass between the hot side and the cold side of the system. As less heat is demanded, more hot water simply circulates in the system in the boiler room.

My approach. A variable speed pump replaces this primary pump. A differential pressure sensor looks at the pressure across the pump and adjusts speed to just supply the water needed for heating demand. The loops are generally of similar length and have flow adjustments available to balance flow at a given pressure.

The problem. I finally installed (just a jerry rig for now) a filter to get rid of the < 0.25 micron crap in my well water. Works just fine. I could now fill the heating system. I did. We made hot water last week. The control systems are not active except for the previoulsy mentioned differential pressure controller. Looked OK. House got hot. Tried turning off some hot water circuits. Differential pressure does not remain constant. Oops.

Read specs of equipment supplied by contractor (I know, I know - but the contractor is competent and I have many other problems). He installed a pump controlled by a 0-10V input and a differential pressure sensor that provides a 0-10 V output. The problem - it ain't a control loop. There is no set point/feedback. The pressure sensor is just that. A sensor. No feedback loop. If differential pressure goes up, so does the pump speed (or down, there is a switch to reverse response and that is probably on). It hits equilibrium, but there is no control that determines what that point of equilibrium will be. It needs to be a specific water pressure (head, for the heating people).

I am Googling my little fingertips off to find a solution. I need a system that controls the pump to reach a setable pressure point. An ancillary issue is the noise of the variable speed circulating pump. Based on the listing of a starting capacitor value, it is a SCR/TRIAC control of an AC motor rather than a brushless DC PWM motor. It vibrates a lot. This seems like the wrong approach, but I don't have an alternative. I would like to minimize throwing away expensive components but the solution needs to be one the inspector will not have a problem with. They like things built by other people and having standards compliance lables. I can also leave it alone and fix it later.

OK. If you are still out there, gnaw this bone to the nub like you did the last one.