multiple pressure switches

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diz71266

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My building has a booster pump to raise water pressure because its located near a water tower..why do they have a electronic pressure switch (SquareD 30/50) And a Mercoid pressure switch...why does it need 2?...just curious...the building has 12 apartments
 
Just for further info, i noticed the mercoid switch is installed prior to the booster pump and the Square D 30/50 is located after
 
We would need more information than you've given, but the difference between the Mercoid and the Square D 30/50 besides cost is the fact that the Mercoid can be dialed down to a differential of about 5 lbs. A simple flow switch might be a better solution.
 
From what ive been told its a double failsafe installation so that if the pressure going into the pump changes the mercoid switch regulates the pump...the 30/50 controls all building supply pressure after the pump...i guess that seems to make sense.
 
I have never known a Mercoid (that I'm familiar with) to regulate other than on and off. You wouldn't want a pump motor going on and off rapidly as in regulated by pressure unless there were some sort of storage tank to keep the cycles to a minimum.
 
Yes there is a bladder tank... From the way its plumbed the Mercoid is only monitoring/regulating the incoming pressure, which I would think wouldnt fluctuate too much coming off of a water tower...but I could be wrong.
Clearly, the 30/50 regulates the pressure from the pump to the fixtures.
 
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