Pressure switch 30/60? Why 20 PSI range
- Thread starter Gary H
- Start date
LLigetfa
DIYer, not in the trades
It may overstretch the diaphragm if it doesn't have an internal dome limiter.
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Fitter30
Well-Known Member
Also find the differential will be really noticeable. The draw down between 30-40lbs unless tank is a lot larger doubt if the difference was a gallon take less than 30 seconds.
Bannerman
Well-Known Member
The diaphragm within a pressure tank is typically designed to allow sufficient deflection for ~20 psi differential pressure, without subjecting the flexible diaphragm to excessive stretch or stress (premature failure). In addition, the pressure range difference occurring with a 20 psi differential pressure is bad enough, so a 30 psi delta, would be excessive and unacceptable to many people.
The pressure switch range setting maybe adjusted, but the air pre-charge pressure in the pressure tank will then also need to be adjusted accordingly. The pre-charge pressure setting for a submersible well pump is usually 2-3 psi lower than the pressure switch Cut-In pressure (ie: 40/60 = 38 psi pre-charge), but may need to be as much as 5 psi lower for a jet pump.
As many prefer constant pressure, and to eliminate pump cycling, the best method will be to utilize a Cycle Stop Valve equipped with a tiny, 4.5 gallon pressure tank. As the tank will hold only ~1-gallon draw-down, only one gallon use will cause the pressure to drop from 60 to 40 psi, thereby causing the pressure switch to activate the pump.
Once the pump is activated, the CSV will maintain a constant 50 psi downstream, by limiting the flow rate from the pump to precisely equal the water consumption flow rate. The pressure to fixtures will remain a constant 50 psi, and the pump will not cycle, regardless if water is being utilized continuously for 10-minutes, or 10-months.
Once no water is further being consumed, the CSV will permit only 1 gpm to pass through, thereby allowing a further 0.5 gallons to enter the pressure tank in ~30-seconds, which will cause the system pressure to build to 60 psi, and the pressure switch to shut off the pump.
The pressure switch range setting maybe adjusted, but the air pre-charge pressure in the pressure tank will then also need to be adjusted accordingly. The pre-charge pressure setting for a submersible well pump is usually 2-3 psi lower than the pressure switch Cut-In pressure (ie: 40/60 = 38 psi pre-charge), but may need to be as much as 5 psi lower for a jet pump.
As many prefer constant pressure, and to eliminate pump cycling, the best method will be to utilize a Cycle Stop Valve equipped with a tiny, 4.5 gallon pressure tank. As the tank will hold only ~1-gallon draw-down, only one gallon use will cause the pressure to drop from 60 to 40 psi, thereby causing the pressure switch to activate the pump.
Once the pump is activated, the CSV will maintain a constant 50 psi downstream, by limiting the flow rate from the pump to precisely equal the water consumption flow rate. The pressure to fixtures will remain a constant 50 psi, and the pump will not cycle, regardless if water is being utilized continuously for 10-minutes, or 10-months.
Once no water is further being consumed, the CSV will permit only 1 gpm to pass through, thereby allowing a further 0.5 gallons to enter the pressure tank in ~30-seconds, which will cause the system pressure to build to 60 psi, and the pressure switch to shut off the pump.
Anytime I see a wide pressure switch band width I know someone is trying to keep the pump from cycling on/off so much. As was said, adding a Cycle Stop Valve will solve the problem. Anything else is just a temporary Band-Aid.
Chucky_ott
Active Member
You also need to make sure your pump is capable of producing the pressure you set as your cutoff pressure.
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