Pressure switch cuts on & off

[traveling man]

Gentlemen:

Had a new pump and motor installed 3 months ago. All was well until now. The pressure switch for the pump gave up the ghost and I replaced it. The switch is 20 on
and 40 off. Measured the tank pressure right after installing switch and it was 5. Turned on the power and the switch turned the pump on and ran for a while. Now when I turn on the hose the switch will come on for 2 seconds and shut off. Sign on the tank says tank pressure should be the same as the cut on pressure which is 20. I fiddled with the tank air and it is exactly 20. The problem still continues. Turned off power to keep from overworking the pump. I sure do need some help quickly. Anything you could do really would be appreciated.

Traveling Man

 

[Gary Slusser]

I'm not sure I fully understand the problem as described but...

Turn off the power to the pump. Shut of the water to the house past the pressure tank. Drain the pressure tank of all water. Now would be a good timto flush the tank by turning on the power to the pump for 5 seconds with the drain open and shut off the pump allowing all the water to drai and repeat until the last bit of water fom the tank is as clear as possible. With the tank empty of water and a known good air pressure guage, check the air pressure in the tank. It should be 1-2 psi below the cut-in setting of the switch. I.E. 20/40 gets 29-28 psi air pressire with no water in the tank. If the air isn't 1-2 psi less than the cut-in setting, then the tank will empty before the pump comes on.

Before checking the air pressure, vent a spritz of air and if you get water vapor or water, the tank's bladder is bad (assuming a captive air precharged tank); replace the tank. Check the air pressure to be correct for your switch settings as you install any new tank.

You may want to run water until the pump runs and shuts off remembering the cut in and out pressure readings before doing anything above to make sure of the switch settings, 20/40 etc.

 

[Sponsor]

 

[Rancher]

It should be 1-2 psi below the cut-in setting of the switch. I.E. 20/40 gets 29-28 psi air pressire with no water in the tank. If the air isn't 1-2 psi less than the cut-in setting, then the tank will empty before the pump comes on.

One correction to Gary's numbers, and I'm sure it was just quick typing. But the air pressure in the tank should be at 18-19psi, not 28-29psi.

Rancher

 

[traveling man]

Thanks guys,

Changed the pressure in the tank and the problem is solved.

Traveling Man