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Submersible Well Pump question

Submersible Well Pump question

Submersible Well Pump question

(OP)
What will happen in a submersible well pump installation containing a pressure tank at the top (floor level) if the air in the pressure tanks leaks off (not air at all)?

RE: Submersible Well Pump question

The same as any other pump would behave when the inlet head reduces because of reduced inlet pressure into the pump.

A sketch would help a lot....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)

RE: Submersible Well Pump question

(OP)
the air I am referring to is the air precharged in the pressure tank (5)

RE: Submersible Well Pump question

All depends what your flow out is like.

All this will change is that the outlet won't have any pressure maintenance and so any small usage or leak will lower the pressure very quickly and hence the pump will start, pump for a few seconds to pressurise the system again then turn off.

Sop you pump could get a lot of starts. If your outlet opened for flow the user would get a spurt of water then nothing, then lots of water as the pump kicks in.

The accumulator with air in it smooths all of that out.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
the pump works 24hs a day with out stopping even when nobody is using water (this is a house installation)
The pressure never reaches the cutoff pressure set at the pressure switch (4 bar). Pressure stays at around 3 bar all the time
If pressure tank has a precharged 0 bar (no air) the the pump will start and stop very often (as you said LittleInch).

I think that there is a 2nd problem here (besides no precharge at pressure tank). I am suspecting that the pump is spinning at the wrong way. Does submersible pump have spinning direction or they work the same in both ways?

RE: Submersible Well Pump question

OK,
The options are:
Your pump is either spinning the wrong way ( only really possible if you have three phase supply),
Your pump is undersized for your requirement (cannot reach 3bar at no flow)
Your pressure set-point is too high ( reset to 2.5 bar?). Why is this so high? for a domestic propert you don't normally need 3 barg
Your pump has a fault
Your electric supply is the wrong voltage or frequency for the motor

Does this help?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
yes. It helps a lot
The pump is 3 phase supply and it`s been connected a couple of days ago
The pump is not undersized. Same size of pump has been working for long time w/o any problem
Pressure value is high but this is not the problem because the pump used to reach this pressure w/o problem
Pump has a fault: dont think so. Is a new pump
Electric supply: ok

I think that it is spinning the wrong way. Tomorrow I will change rotation direction and see what happens




RE: Submersible Well Pump question

Just change over one pair of the three phase wires, I think to change the rotation. Don't know how you'll see the rotation of a submersible....

Let us know how it goes. Sounds like it might be the answer - typically you'll get about 60-70% of the proper head by spinning the wrong way so you should get about 5 bar?

Double check the required voltage and frequency of the pump match the previous unit. Also just because the pump is new doesn't mean it isn't broken or has a fault. The difference between a 50htz unit and 60 htz unit is quite large.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
I plan to invert position of 2 wires, run the pump and see how it behaves by looking at the pressure gauge
If cutoff pressure is reached then this was the 1st problem
Then I will precharge the air tank and check pump on/off cycles

RE: Submersible Well Pump question

Do you know the water level in the well? The pump is selected based on the water level in the well and the elevation that you are pumping to.

RE: Submersible Well Pump question

there are other possibilities, for instance you could have a leak in a joint or fitting within the well. in that case, water would be going in circles but you may not build full pressure at the surface

RE: Submersible Well Pump question

Sounds like the house I grew up in, the pressure tank would leak air, we'd have to recharge it every 6 months or so.

The whole point of the air in the tank is to provide a pressure buffer. Without the air, the instant the water is turned on at a faucet, the pressure drops enough to kick on the pump, the pump will instantly overcome the cutoff point (because the pump generally has a higher capacity than the flow out of the faucet). As long as there is any demand on the system, the pump kicks on and off every few seconds. This can burn out or overheat the motor quickly.

To address your question about the pump never reaching the 4 bar pressure, as others have said, if it's a 3 phase supply, switch any two leads, and see if that helps.

RE: Submersible Well Pump question

"this pump works 24 hrs a day"
Do you mean it runs continuously 24/7?.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Artisi - I think he's probably wondering why he's getting hot water from the cold tap....

It has only been installed for a couple of days so maybe hasn't burnt the motor out yet.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

You have the pressure gauge set at 4bar correct? Reset it to a bit under 3 bar and monitor the result.

Is this tank a bladder tank, ie., a diaphram between the air and the water?

A pump curve would be helpful as would contacting your local domestic water supply guy for some advice.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Since we enjoy being pedantic, how does one 'set' a pressure gauge?

RE: Submersible Well Pump question

Tenpenny:good one, please accept my sincere apologies, that of course would read better as pressure switch.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

(OP)
I checked direction of rotation. Pump is spinning correctly
Pressure tank: Has no air at all. I have dismounted and disassembled the tank. The bladder is good
Pump works with out stopping and pressure stays at 3 bar

Bimr: I do not know the water level in the well
cvg: I didn't think about that. Thanks!
Artisis: yes 24/7
This is the tank: LS H 60

http://www.varem.com//pg.asp?cd=1014&mnpath=/0...=

I am going to precharge the tank again, install it and see what happens


RE: Submersible Well Pump question

If the bladder is good, where has the air gone?

PUMP CURVE,WHERE IS IT?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Why is the pressure switch upper setting 4 bar, by design, default or ponder.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Seems like the problem must now be resolved,always nice to get the usual feedback - silence.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Give him or her a chance. Been a member for 7 years and hundreds of posts and replies so should understand what we're at.

Not everyone logs in as much as some of us do.....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
Artisi
Air must have leak out through the air valve. I changed the seal of it
I have installed the pressure tank and the pressure still does not raise above 3 bars. I reset cut OFF pressure to 2,8 bar and cut ON to 1,0 bar. The system seems to be working good so far but pump pressure used to reach 4 bar.
I dont know who or why it was set to 4 bar
I dont have the pump curve. All they could told me is that is a 1 HP SAER pump

RE: Submersible Well Pump question

Lukin,

Glad to hear you've fixed it.

To be frank, if that's the level of technical knowledge coming back from the supplier / installer, then how they can actually say this is "identical" to the one you replaced is pushing it. I had a quick look at the SAER website and there are not only many types of pumps available, there are many versions of those pumps. There are a number of ways a "1hp" pump could be configured to give you a slightly lower outlet pressure.

So unless you can get the model number, pump curve and then compare it to your old one, I wouldn't bother any more. You have running water and the pump turns off until it's needed. Job done.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
yeah. I think the same, the only thing that remains to be corrected (change) is the size of the pressure tank because pump ON time is only 10 seconds to get from 1,0 to 2,8 bar. Seems to me that the tank is small for this pump
Pressure tanks is 60 liters and only half of it is filled with water (estimated)
Precharged pressure is 2 bar (I should lower precharge pressure to get more water into the tank)
Any comments?

RE: Submersible Well Pump question

Prior to operation, with the tank, empty of water, the pressure should be 2 psi below the cut-on pressure. So, for example, with a 30-50 pressure switch (factory default setting), air pressure in the tank will equal 28 psi. If the pressure switch is adjusted to 40-60 psi, the cut-on pressure will be 38 psi. Set the pressure switch to reflect a 20 psi differential between cut-on and cut-off. If the pump cycles too quickly causing the pump to cut on and off, setting the pressure switch to a higher on/off setting should slow down the cycling.

RE: Submersible Well Pump question

(OP)
thanks bimr
will do that tomorrow

RE: Submersible Well Pump question

(OP)
so I managed to get more information about the installed pump

SAER type B12
6400 lts/hr at 25m
1600 lts/hr at 50m

RE: Submersible Well Pump question

The turn-off pressure setting should be set about 5 psi lower than the deadhead pressure of the pump. This way the pump will not turn-off as long as there is some minimal water flow is being used. This is needed to prevent short-cycling. If the pressure switch is set to a point in the flat section of the pump curve the pump will cycle on/off while using any water unless the flow exceeds the capacity of the pump. A good example is taking a shower. Your water usage will be well below your pump's capacity. You do not want the pump cycling during the shower. It is bad for the pump and your water pressure will also vary. When you set the pressure switch correctly, you do not need a large pressure tank.

The pressure tank needs to be filled with air when there is no water in the tank, and the air pressure should be a little higher than to the pressure required for the pump to turn-on.

RE: Submersible Well Pump question

Set-up for pressure switch and tank pre-charge.

1. The cut-in pressure for your pressure switch should be the sum of the pressure required at the highest point in your system (ie, maybe showerhead) plus the elevation from the pressure tank to the highest point plus a bit for friction losses in the pipework.
2. The cut-out pressure to equal the cut-in pressure, plus 1 -1.5 bar, BUT NOT exceeding the maximum head the pump can deliver at the tank, this is measured from water level in the well plus friction loss to the tank plus the cut-out pressure setting.
3. The tank air pre-charge should equal approx. 90% of the cut-in pressure. (ensure there is no water pressure acting on the diaphragm).

Set your system up as above and you should have a smooth and fully operating system.

P.S. Do you know the operating ground water level, this is an important piece of data, if unsure, possibly you can test the developed head pressure against a closed discharge valve at ground level or at just prior to the pressure tank -- the pressure at this point may influence your overall system -- it is required information.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Submersible Well Pump question

Something isn't adding up here.

The tank is supposed to be a 60 litre tank. The link provided by the OP gives an excellent formula for working out the volume of a pressure tank

However for a tank to go from 1 bar to 2.8 in 10 seconds would mean a volume change of around 20litres according to the tank website = a flow in of 120 l/min.

Maximum flow from the pump is only 46, but at what you can only assume is that it is working close to max head, flowrate is circa 15 to 20 l/min, hence 10 seconds of flow = 2.5 to 3 litres.

It doesn't sound possible for a 60 litre pressure tank to go from 1 to 2.8 bar with only this volume unless the bladder is very small or the system is somehow compromised.

lukin, your pump data implies that the water level is 60m below your tank level ( max head 92m, static head 3 bar). Does that sound right?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Submersible Well Pump question

(OP)
LittleInch: I dont know exactly how deep is the well but the owner says is between 50 and 80 meters
I could not go to the site today. I will check myself how long does it take one ON cycle next thursday

RE: Submersible Well Pump question

(OP)
I was at site today and measured the time it takes to the pump to stop
It takes 1 min and 30 segs to go from 1 bar to 2,8 bar

RE: Submersible Well Pump question

Sounds much more like it. Hope it's all working well now.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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