Pressure switch questions

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Old 07-27-13, 06:19 PM
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Pressure switch questions

I've got a 220 (single phase) submersible 5 hp pump and a 30-50 pressure switch that was hooked up by the guy who installed the pump. The pressure switch failed (contact burned out) and I need to replace it.

Most of the stuff I've seen online shows 4 wires going to the pressure switch--2 on each side. Mine has only two wires coming from the control box (plus ground), and the installer put them both on the same side. Does it matter if they are both on the same side or should I put one on each side of the pressure switch?
 
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Old 07-27-13, 08:03 PM
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Normally you would bring the two supply lines into the switch first and then the two load wires to the pump or pump control box. Switching just one half of the 240 v will get the job done but isn't the way it's normally done.

In the picture below.... 1 and 2 are one switch and 3 and 4 is the second switch. So if you are just switching two wires you would use 1 and 2 or 3 and 4.

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This switch is wired correctly.
The line (red and black) is connected to 1 and 3.
The load (red and black) is connected to 2 and 4.
 
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Old 07-28-13, 09:15 AM
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Thanks for the precise and concise response.

This is what the old contact looks like. It's burned on the side that the two wires were connected. Could that have caused it to burn?

Or could it have been a faulty pressure switch?

Or could there be something wrong in the control box?
 
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Old 07-28-13, 03:28 PM
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Once the contacts start to pit/arc ........ it's downhill from there.

One problem that can shorten the life expectancy of a pressure switch is short cycling. That would be caused by a pressure tank issue.
 
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Old 07-28-13, 10:03 PM
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You only have two wires because there is a contactor in the control box. The two wires that are on the switch activate a coil that sends power to the pump.
The contactor can take more amps than the pressure switch.
The coil may be 110 or 220 volt. a loose wire or bad connection on the pressure switch can cause the to burn like that. Or a bad coil (short or grounded coil) in the control box can also cause the burn.

If you dont have the coil in the control box, it is wired wrong and should be wired like the picture above.

Here is a picture of what the contactor may look like.
 
 

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