Situation: wiring a remotely located sump pump and a remote in-tank float switch. My boss says to me (ya know, cuz I’m stoopid) “Make sure you use the float switch to break the neutral. You don’t want to break the hot because then there’d be juice in there. If the float ever fails, you’ll energize the whole tank!”
First - who DOESN’T break the neutral that this would need to be said?
Second - I used the float to break the neutral on a 3 phase motor starter circuit (so, the neutral for the starter coil), and when I went up to the junction box above the remote tank to check the wiring before final startup - guess what! There was 120V present on one side of the float (the side which was coming from the"neutral" on the motor starter coil).
Third - it wouldn’t energize the whole damn tank. He’s stupid. It’s blow a fuse elsewhere in the circuit, or do nothing. Right?
So what gives? Why would he say what he said when the current was there anyway? And how is it more safe to break the neutral in that case than the hot? There’s juice there anyway. It’s waiting to get through the float switch to find ground.
I’m not all that familiar with wiring float switches, but in 20 years as an electrician, I never once had the occasion to switch (open) a neutral in an energized circuit. It’s just not a very safe practice, IMO. Regardless of which leg you open, there is going to be voltage present, so why confuse things by breaking the neutral and letting the next poor sap who works on the circuit get nailed?
I don’t recall any switch wired up to break the neutral. I suspect it violates code. But you are right, the voltage is there in the neutral.
As for 3 phase control voltage, isn’t it usually coming off a transformer and a floating voltage?
Unless you have a license at risk for violating code, I would wire it up the way the boss wants to keep him happy. Do see to it that the pump housing and tank are grounded if metal. I am surprised how high resistance to ground ordinary tap water is if you want a ground. Yet it seems to conduct fine when it comes to killing people.
you can switch a neutral as long as you also switch all the hot conductors as well. using a multipole switch is OK.
you want to use motor, switches and cabling suitable for submersion where it is submerged or is possible for it to be submerged. you would want to use switches and cabling suitable for wet locations if it can never be submerged but is in a wet environment. a sump tank or contents should not be able to be energized by any circumstance.
You want to switch the hot, not the neutral. If you switch the hot, no energized lines should be past the switch - the neutral should be near groud potential, and the switch leg should be too. If you switch the neutral, 120V is still present on the hot wire to the relay coil, and that potential “goes through” the coil and back to the switched neutral up to the switch. The coil is a relatively low resistance, and can complete the circuit connecting a person to the hot if the switched neutral is touched.
This is why switching the neutral is generally only allowed if you also switch any hot wires with a multipole switch.
True enough; I’d forgotten about multi-pole switches, which I did wire in my career. It’s been over 20 years since I actually worked in the trade. You never forget the first time you open the neutral line first on an energized circuit, though; it only takes once to get your attention.
Well a standard sump pump like you buy at the homey-depo has a float which does precisely that, break the neutral. I can’t imagine any other way of utilizing a float switch to interrupt pump operation. What am I missing?
I work with electrical equipment all the time for my job - I’m a service tech and electrically controlled equipment breaks all the time. I’m not a licensed electrician, but I’ve never violated any codes, and I’ve never had anything not work. If it seems sketchy, I defer to a more experienced person. But my boss’s comment threw me for a loop because it seemed obvious…and then when I double checked it, the voltage was there anyway. Which I figured…
And what’s this nonsense about not using a switch to interrupt the neutral on a circuit? How else would you interrupt operation?
In standard residential and industrial wiring, you switch the hot leg except for special circumstances as described above. Surely you’re not telling us that you switch the neutral for a lighting circuit? The general rule for working on energized (or even de-energized) circuits is: connect ground, neutral, then hot. When disconnecting: hot, neutral, then ground. There’s a good reason for that sequence of operation.
Can’t speak to your sump pump question, as I don’t have a copy of the NEC any longer. There are exceptions to many standard code requirements, so you may want to consult your copy.
I hardly ever do any residential wiring, but the few light switches I did wire up I broke the hot.
And come to think of it…every single wiring panel I’ve ever been in always had the operator switches breaking the hot.
It’s only ever been at this job, working with in-tank float switches that he’s had me breaking the neutral as a matter of gospel. And it’s always been done that way at this job. And I’ve never thought of doing it any other way at any other job…must have just been natural enough to never need to think about it. So his initial comment baffled me…about there “being juice in there” if I broke the hot…because it would be there anyway!!!
There have been occasions though where a float switch got burned up because someone else wired it up and they used the float to break the hot. … :dubious:
The only time (industrially) we ever break the neutral, is with an overload contact on a motor starter… If the overload trips, the neutral to the coil is broken. Even this practice is going out of favor though, as in the event of a trip it leaves the hot supply present on the control circuits.
The line of reasoning of your boss is probably because in the event of a motor winding fault to ground, the switch won’t burn up, where it would if you switched the hot side. Even so, it’s not a good idea.
I’m still confused… why would switching the neutral be considered better or safer than switching the hot?
Assuming single phase…
If the switch is on the hot, and you open the switch, one side of the switch will be hot, and the motor will be at ground potential.
If the switch is on the neutral, and you open the switch, one side of the switch will be hot, and the motor will be at 120 VAC relative to ground (though it will not be running).
Unless I am missing something, #1 is clearly safer than #2.
I’m trying to figure that one out too. I’ve used float switches to control a contactor for three phase, but I’ve never interrupted the neutral and left the three phases live, only the neutral being switched. It’s a very quick way for someone to get a serious shock.
That is assuming that I’m reading what you said correctly. You’re leaving the power live, but breaking the neutral only with a float switch?
Is your neutral system grounded or floating? That also comes into consideration, as neutral that is ungrounded can develop a significant potential.
I’m a bit of a fanatic over earth grounds at regular intervals, but that was from catching a pretty stiff ground differential once, where the earth grounds were about 300 feet from one another and I stupidly grabbed the connecting line in each hand, VERY briefly. :smack:
I hear all of you. Thanks for the responses. Ignorance is slowly dissipating!
But, the question remains if anyone does know, with a standard commercially available sump pump a la home depot, does the float that is mounted with the pump break the neutral or the hot? It’s the piggy-back plug style float I’m curious about. Maybe it was a misunderstanding of the way these are wired that led my boss to be so adamant about his neutral-breaking.
No no no, ***I’m ***the one confused here Only one confused person at a time.
I see your logic, and I raise you stupidity! I’m beginning to think it’s a vastly underwhelming knowledge of electrical circuits that got my boss to where he is today. In any case, I’ll be breaking hots from now on. (that’s what she said)
My sump pump float failed in the on position. I bought a stand-alone pump float (i.e. plug it into the outlet, plug the sump pump into it). I just checked, and it switches the hot.
I see.
Only one confused person at a time.