multiple pressure switches

[diz71266]

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

 

[diz71266]

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

 

[speedbump]

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.

 

[diz71266]

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.

 

[speedbump]

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.

 

[diz71266]

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.

 

[speedbump]

Can you take pictures and post them?