DC DPST? Question

[noercarr]

I would like to wire up a water pump to 2 switches inside a camper van. If I'm standing in the kitchen, I can turn on the pump to do dishes, then off when I'm done. If I'm at the rear, I can turn on the pump to rinse off with the hose.

Is a double pole single throw switch what I need here? How does the wiring look on that for DC? I've done several AC 3 way switches but for some reason, I get completely thrown with DC wiring.

 

[American Locomotive]

As long as you don't need to be able to remotely turn the pump off from another location, you just need two SPST switches. Supply each switch with battery voltage, and then run the other wire from each switch to the pump. Tie the two positive wires together at the pump's positive terminal.

 

[joe_padavano]

This is no different from wiring three way switches for an AC light circuit. You simply need two SPDT switches in the power feed, one at the kitchen and one at the rear. AC vs DC is irrelevant. Don't overthink this.

 

[joe_padavano]

Yes, it really is this simple

 

[nehog]

Suggestion, add an indicator light (or two) to the output of switch #2 so you can see at a glance whether the pump has power or not.

 

[noercarr]

This is no different from wiring three way switches for an AC light circuit. You simply need two SPDT switches in the power feed, one at the kitchen and one at the rear. AC vs DC is irrelevant. Don't overthink this.

Just watch me! haha

Well in AC, theres 3 wires, dc two so not exactly the same. I also have to tie in my neutral in AC, where as my ground in DC can just be tied into the closest bare metal ground.

The poster above you said SPST, you're saying SPDT. Not sure I need DT, and the image you posted I believe is ST, correct?

 

[noercarr]

This is no different from wiring three way switches for an AC light circuit. You simply need two SPDT switches in the power feed, one at the kitchen and one at the rear. AC vs DC is irrelevant. Don't overthink this.

Suggestion, add an indicator light (or two) to the output of switch #2 so you can see at a glance whether the pump has power or not.

So this is the switch I'm using: https://www.amazon.com/dp/B000Y87W54/?tag=atomicindus08-20

The third input has me more confused now, but it has the indicator light you suggested.

 

[MikeF2316]

If you want to be able to turn the pump on at one switch, then off at the other, you need SPDT switches. If you will always turn the pump on, then off with the same switch, then SPST switches will be all that's necessary. In the latter case, once one switch has turned the pump on, the other will have no effect.

 

[joe_padavano]

Just watch me! haha

Well in AC, theres 3 wires, dc two so not exactly the same. I also have to tie in my neutral in AC, where as my ground in DC can just be tied into the closest bare metal ground.

The poster above you said SPST, you're saying SPDT. Not sure I need DT, and the image you posted I believe is ST, correct?

The switch I showed in my diagram is Single Pole DOUBLE Throw (SPDT). A "three way" switch in an AC light circuit is also an SPDT switch.

The third wire in the A/C circuit is the neutral (return), which is simply the metal frame of the RV in the DC version. You can't use the wooden studs of a house as the electrical return, thus the third wire. In the DC version, you COULD run a separate wire from the pump all the way back to the battery negative terminal. Does THAT make it look just like the AC version to you?

 

[noercarr]

If you want to be able to turn the pump on at one switch, then off at the other, you need SPDT switches. If you will always turn the pump on, then off with the same switch, then SPST switches will be all that's necessary. In the latter case, once one switch has turned the pump on, the other will have no effect.

This makes sense now, thank you. Yes it will be on then off at the same location, so I see how the spst works here.

 

[noercarr]

The third wire in the A/C circuit is the neutral (return), which is simply the metal frame of the RV in the DC version. You can't use the wooden studs of a house as the electrical return, thus the third wire.

Agreed, which is why this seems different to me.

In the DC version, you COULD run a separate wire from the pump all the way back to the battery negative terminal. Does THAT make it look just like the AC version to you?

YES, actually. And I do not want to ground to the frame, so that's very likely what I'll be doing.

 

[joe_padavano]

Agreed, which is why this seems different to me.


YES, actually. And I do not want to ground to the frame, so that's very likely what I'll be doing.

The system is ALREADY grounded to the frame. The return "wire" is just steel instead of copper. There is NO DIFFERENCE between the two as far as wiring this pump.