Different Wire Sizes In Bilge Pump Circuit

[cburger]

I was installing a 2000gph Rule pump in my bilge today. The wire gauge is different from the float switch to the pump wires, from the pump wires to the 3 position switch, should this be a concern to me?

[delmarrey]

Originally Posted by cburger

I was installing a 2000gph Rule pump in my bilge today. The wire gauge is different from the float switch to the pump wires, from the pump wires to the 3 position switch, should this be a concern to me?

All wires to the pump should be the same size, or larger would be even better depending on the length of run. You may have to upgrade to a different float switch.

[four winds]

The float switch wires would have much less current traveling through them than the other wires. The main switch wires have the current that runs the pump motor traveling through them.


I don't think you have a problem based on this reasoning.


edit, I was typing while delmarry was posting. But I'm thinking the float switch wires are only "local" to the pump, carrying current to keep the pump engaged. And not coming from the main power bus, and powering the pump armature.

I could be wrong to assume the pump motor current does not travel through the float switch.

[cburger]

Originally Posted by four winds

The float switch wires would have much less current traveling through them than the other wires. The main switch wires have the current that runs the pump motor traveling through them.


I don't think you have a problem based on this reasoning.


edit, I was typing while delmarry was posting. But I'm thinking the float switch wires are only "local" to the pump, carrying current to keep the pump engaged. And not coming from the main power bus, and powering the pump armature.

I could be wrong to assume the pump motor current does not travel through the float switch.

The supply wires run to the float switch wires and I am pretty sure the float should be sized the same size wire. What I find surprising is the Rule three position switch has very small wires maybe 18 gauge. I am concerned this upsizing and downsizing of wires is a recipe for poor pump performance as well as a potential fire hazard ?

[cburger]

Originally Posted by delmarrey

All wires to the pump should be the same size, or larger would be even better depending on the length of run. You may have to upgrade to a different float switch.

Del, this is what I was thinking, the problem is the 3 position Rule switch has wires that are much smaller than the pump wires.

[delmarrey]

Originally Posted by four winds

The float switch wires would have much less current traveling through them than the other wires. The main switch wires have the current that runs the pump motor traveling through them.


I don't think you have a problem based on this reasoning.


edit, I was typing while delmarry was posting. But I'm thinking the float switch wires are only "local" to the pump, carrying current to keep the pump engaged. And not coming from the main power bus, and powering the pump armature.

I could be wrong to assume the pump motor current does not travel through the float switch.

Partially true! DC voltage flows one direction. So if the switch is on the down hill side then it's fine as long as the pump doesn't short out. Then the fuse should take over if rated properly.

[delmarrey]

I my younger daze I use to rebuild alternators and starters. Voltage was always assumed to flow from Neg. to Pos. And that was the reason for putting fuses on the Pos. side of equipment, so if it over loaded the excess power passed thru the equipment and blew the fuse instead of burning up the equipment.

Only diodes will change the direction of the flow, like in a rectifier, making AC voltage.

[fkittson]

I have worked will Rule pumps and float switches for years. When I contacted the manufacture about this they said two things:
1- The float switch was designed for that gauge of wire. (if you take apart the switch you will void the warranty)

2- The three way switch was designed specifically for there pumps so no need to worry.

In the last 10 years that I have used rule pumps I have never had a single sinking, high water, fire, short in the wiring. As long as you check your float for sticking every once and a while. As well as keep the area clean you won't go wrong.

[delmarrey]

Here take Don's advice.......> Installing a Bilge Pump by Don Casey

[cburger]

Originally Posted by delmarrey

Here take Don's advice.......> Installing a Bilge Pump by Don Casey

Del,

This is what I used to refresh my memory regarding the switch wiring.

However I still feel that having smaller sized wires downstream from larger wires goes against good electrical theory? If I size the wire gauge correctly for the length of the wire run and amperage draw of the pump and lets say the wire that is called for is a 12gauge and this runs to the Rule switch that is wired with what appears to be 18 gauge wire that smaller wires create resistance, that eaquals heat and the possability that the pump won't be getting the full 20 amps required for full perfomance ??

[mikefossl]

Perhaps we can look at it like this: The larger gauge wire is used to provide a lower resistance based on the longer run. The smaller wire doesn't add that much more resistance because the run is much shorter. It's the over all resistance of the both sets of wires that determines the voltage drop that the pump motor "sees".

[delmarrey]

It says right on Don's site...............

Don't skimp on wire size
A 3,500 gph pump will draw 15 amps, typically necessitating 10-gauge, or maybe even 8-gauge wire. Consult the ABYC Wire Size Table to determine the appropriate wire for your pump and length of wire run.

[David M]

I have noticed the same thing about float switch wires and thought the same thing. I went ahead and wired it up anyway and had no problems.

I agree with Mikefossl.

[cburger]

Originally Posted by delmarrey

It says right on Don's site...............

I understand this, that's whys I asked the origional question. So what do you do about the the other components that come from the manufacturer with much smaller wire sizes that will be part of the circuit? Do I have to make my own switches?

[fkittson]

No as the other person said the 18 gauge wires on the switch are so short they are sized correctly