Submersible 2 Wire Well Pump Versus 3 Wire

If you have a submersible well pump (located in the well itself) you will have either a 2 wire or 3 wire pump.

2 Wire Vs 3 Wire – What is the Difference?

Both types of pumps work exactly the same way – the only difference is the location of the relay and start capacitor and how many wires need to go out to the pump.

For the pump to turn on, it needs a relay and a start capacitor.

  • In a 2-wire pump, the relay and start capacitor is located IN the pump itself and the pump is in the well.
  • In a 3-wire pump, the relay and start capacitor is NOT in the pump but usually in your basement inside a Control Box. The pump, of course, is still in the well.

Technically speaking, your pump capacitor needs electricity to start. The electricity comes from your pressure switch located near your Pressure Tank. When your pressure switch is activated, it sends the signal to the start capacitor which is either in the pump (for a 2-wire) or in the control box (for 3-wire).

submersible well pump

Ironically, a 2 wire pump actually has three wires coming from your home to the pump (two hot and one ground). A 3-wire pump actually has four wires going into the control box and 4 wires going to your pump.

Below is a Control Box . Inside is the Relay and Start Capacitor.

control box for submersible well pump

Benefits of a 2 Wire Over A 3 Wire Pump

In H2O’s experience, we find the 2 wire pumps to be more reliable and robust. The pumps themselves tend to be less expensive, and the wire is less expensive (2 wire vs 3 wire) The only downside is the entire pump will need to be replaced IF the start capacitor fails.

Three wire pumps have an advantage that if the start capacitor fails – you can replace only the control box located in the basement. However, in H2O’s experience it is rare that only the box needs replacement. Oftentimes, when the Control Box is damaged and fails, the pump is also damaged and fails.

The other difference is that the 2 wire pumps are limited to 1 ½ HP – anything larger will be a 3 wire.

Can You Convert a 3 Wire to a 2 Wire Pump?

Yes. It is easy to install a 2 wire pump on a 3 wire set up, as no new wire will need to be run. The technician can simply cap off the extra wire. If you want to replace a 2 wire pump with a three wire, however, new wire will need to be run and a control box installed.

submersible 2 wire well pump vs 3 wire

If you have any questions regarding what kind of submersible well pump you have do not hesitate to contact us. We would be happy to review your existing account with you, or set up a free consultation if you are new to us.