Submersible Well Pump question

[lukin1977]

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)?

 

[Artisi]

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

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.)

 

[Artisi]

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.)

 

[LittleInch]

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.

 

[lukin1977]

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

 

[LittleInch]

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.

 

[lukin1977]

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?

 

[bimr]

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.

 

[lukin1977]

thanks bimr
will do that tomorrow

 

[lukin1977]

so I managed to get more information about the installed pump

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

 

[lukin1977]

Sorry, now they tell me that the pump is:

http://electrapomp.com/catalog/saer_sondajni_pompi.pdf

page 14

FS-98A/15

 

[Compositepro]

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.

 

[Artisi]

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.)

 

[LittleInch]

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.

 

[lukin1977]

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

 

[lukin1977]

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

 

[LittleInch]

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.