I switched the neutral on my float switch in a cistern

[MillWeld]

Not exactly a tractor job but a tractor did dig the hole for the cistern, so...

I put a float switch in the tank to shut the pump off if the water level gets too low. If I ran the hot wire to the switch (as is certainly standard) and the switch ever leaked then I have a potentially dangerous situation on my hands. A cistern with a 125VAC wire in it... and maybe or maybe not it will draw enough current to trip the breaker.. I didn't want to risk it so I ran the neutral to the switch and labeled the junction box in the crawl space as a reminder to me. What are your comments on this?

The cistern is 500 gallons, collects roofwater for a garden and has been in operation a couple of years. Here is the switch.
Series CFS2 | Cable Float Switch | Dwyer Instruments

 

[RedNeckRacin]

I would look at a submersible pump setup. They usually have a cord long enough to keep anything that's not sealed up out of the water to prevent this situation. And really in a closed tank, the only things moving should be the water and the float.

 

[CobyRupert]

When the switch is off (open), you still have 120 volts to the switch in your tank (i.e. there's no current, thus no voltage drop through the pump motor). The pump motor is constantly at 120v, there's just no current flowing. I don't know what effect this has on life of pump, bearings etc.. Maybe others can comment.
Now if the switch insulation fails, yet the neutral conductor stays intact, yes the voltage of the water shouldn't rise much (probably not much more than a couple volts), but your breaker won't trip, and large animals will still notice.
If the insulation AND neutral conductor fails then: the 120 volts is split by the pump and the resistance of the tank ( example: let's say 50/50 where the motor gets 60 volts and the person touching the tank gets 60 volts) and again: the breaker will Not trip.
The reason the Code does not allow this, other than above reasons, is if the neutral wire becomes grounded ahead of the switch, the motor will run and the switch will not turn it off, which in many applications is bad.
What many don't understand is that you want a large short circuit (into a good ground connection) so the breaker trips.

 

[Apsterbobed]

When the switch is off (open), you still have 120 volts to the switch in your tank (i.e. there's no current, thus no voltage drop through the pump motor). The pump motor is constantly at 120v, there's just no current flowing. I don't know what effect this has on life of pump, bearings etc.. Maybe others can comment.
Now if the switch insulation fails, yet the neutral conductor stays intact, yes the voltage of the water shouldn't rise much (probably not much more than a couple volts), but your breaker won't trip, and large animals will still notice.
If the insulation AND neutral conductor fails then: the 120 volts is split by the pump and the resistance of the tank ( example: let's say 50/50 where the motor gets 60 volts and the person touching the tank gets 60 volts) and again: the breaker will Not trip.
The reason the Code does not allow this, other than above reasons, is if the neutral wire becomes grounded ahead of the switch, the motor will run and the switch will not turn it off, which in many applications is bad.
What many don't understand is that you want a large short circuit (into a good ground connection) so the breaker trips.

This is correct! I would recommend changing the float to the line side and installing a GFCI breaker to protect you from leakage. If you are still concerned use a transformer and RIB (or an all in one power pack) and put the float on a 12v circuit, but I would feel fine with just the GFCI. Their primary use is to protect you from that evil water! :thumbsup:

 

[MillWeld]

Got it. I overlooked that I have 125 VAC in the motor at all times; that's not safe either. I will replace the receptacle with a GFI.

Thanks for the comments. I came to the right place.

 

[Valveman]

It doesn't matter if you cut the neutral or the hot, you still have 120 volts in the water. A GFI makes it safer. A pool guy told me you could hold the hot wire and jump in the pool and a GFI would trip before you get shocked. I wouldn't test it but he is probably right.

However, I always use 24V on a float switch.

 

[Cataclysm]

I setup a cistern to collect rain water off the roof for my folks to water their garden. I used components from/for Clearstream aerobic systems. Here is the pump. Clearstream Pump The cord is plenty long to run up to the access hatch. I use their floats as well. Clearstream Float You might consider using silicone wire lugs as well if your making any connections in the tank.

 

[Industrial Toys]

A very large underground holding tank I am currently involved with has all 24 VAC circuits to the float switches. 24 VAC coils on the contactors.

 

[MillWeld]

My submerged switch has no ground, only 3 wires: common, NO and NC, so there is no way a GFI circuit will work. I will go with a low voltage relay.

 

[Apsterbobed]

GFCI will work without a ground. They monitor what goes out and what comes back and base the trip on a difference. Even if you go low voltage I would protect the source with a GFCI. GFCI are used in older homes that were wired with out a ground conductor to give you the convince of the 3 prong outlet, but they should be labeled no ground.