Need help with Pump Pressure switch shutoff

[LuisC]

I built an RO system that is making 3000 GPD of Clean water. I am trying to incorporate a low pressure and high pressure cut off so I don't burn the pump by running it dry. So the low pressure will satisfy a possible scenario where i loose incoming water to the pump. The pump will run at 120-140 psi and looking to cut off pressure for example at 150 psi.


I found a video on youube depicting what i want to accomplish. Just need to confirm the model # for hte low pressure side. I have found this one from Sqaure D part # FSG2J20M4BP now looking for help on the high side if this one is correct.

This is the video depicting what i am trying to accomplish.

Thanks

 

[Valveman]

The FSG2-M4 is the right pressure switch for the low pressure cut off. He is just using a standard FSG2 without the M4 feature for the high pressure side. I don't know that you can find one any higher setting than 40/60 and you need a 70/90. If you can find a 50/70 you can probably turn it up to work at 70/90. If it were me, I would use a small little 2.2 gallon pressure tank with that high pressure switch.

 

[Sponsor]

 

[LuisC]

I am not running an under the sink RO unit. This is a 2500 Gallons per day Commercial RO, not 300 Gallons Per day. A small tank will be useless to me. I am trying to make 300 gallons of water FAST.

 

[Valveman]

Anytime you use a pressure switch, there should also be a pressure tank. Water lines do not work like a pressure tank. And as long as you are using the water it will flow right past the pressure tank, and the tank is not really needed. But the tank is very important for times when the pump is off. A 2.2 gallon size tank will give you about 1/2 gallon of draw down to use before the pump comes back on. Without a tank, the pump will come back on if you have a few drops leak in the system. A small leak in the system like a leaky check valve or float valve can make the pump cycle on and off as fast as a machine gun. A little pressure tank will keep that from happening.