Re: OT: Well pump wiring

On Thu, 15 Jun 2006 05:46:52 GMT, The Hurdy Gurdy Man
<bryan@xxxxxxxxxxxxxxxxxxxxxx> wrote:

I've got a well. As you'd expect, this well has a pump. It's a 3HP 230 volt
Grundfos unit, and I'm attempting to run power to it. For the most part
this has gone reasonably well, but I'm at the point where I've got a subpanel
with power right next to the well and I have to make that final connection
between the two. I'm hoping someone with some experience with this can
provide me a bit of a sanity check before I go further.

The wiring diagram for the control box implies that one runs power from its
source into the terminals on the pressure switch, which then runs off to
the control box. The pressure switch, and everything after it, was already
wired by the well driller. This all makes sense, but due to the location
of various parts I'd like to deviate from things a bit. Here's the questions:

- It would be easier to run power from the subpanel into the control box
(which is almost the same size as the 6 circuit subpanel), then run wires
within the same flexible conduit that is coming from the pressure switch
into the control box instead of going straight into the pressure switch
housing. Is this a bad idea, or a code violation? The wiring between
the pressure switch and the control box is three 12 gauge copper wires,
which if I ran more wires would bring the total to 5 12 gauge (the ground
would be made in the control box). This is 1/2" FNC, by the way. I
think that's still below 40% fill, but I need to double check my math.

- Does there need to be some sort of special fused disconnect switch, or
does the circuit breaker in the subpanel that feeds the circuit for the
well suffice for this purpose? It's a standard 2 pole circuit breaker.

If it's well marked, the breaker is the disconnect. You can get an
add-on for most modern panels that slips over the breaker handle to
allow for locking the handle in either the Off or On position.

- Although there's 10 gauge wire running down into the well, as I mentioned
above there's 12 gauge stranded copper wire running from the internals of
the control box out to the pressure switch, and as I understand it
the breaker must be sized to protect the smallest conductor in the
circuit as opposed to the load at the end. This would make it a 20 amp
breaker, correct?

You could add an inline fuse-holder inside the control box where the
leads to the pressure switch break off, and then drop to as small a
wire as you want. The pressure switch is "pilot duty" and there's
negligible current - even when you are pulling up the main motor
contactor, the surge is only a couple amps.

--<< Bruce >>--

.

Relevant Pages

  • Re: OT: Well pump wiring
    ... I'd guess a 20 amp breaker will give you nuisance trips. ... I found the one for the control box by doing a Google search ... that a 12 gauge wire takes no more than a 20A breaker. ... I don't know the brand of pressure switch on my well, ...
    (rec.crafts.metalworking)
  • Re: OT: Well pump wiring
    ... Just like an AC Condensing Unit, if it calls for a minimum fuse size ... I found the one for the control box by doing a Google search ... As far as the sizing of the breaker goes, I made a guess at 20 amps for two ... I don't know the brand of pressure switch on my well, ...
    (rec.crafts.metalworking)
  • Re: Changing Breaker Box - Looking for Different Perspective
    ... out a breaker panel in a house without turning off the service power. ... Consider that when you're changing that 120V socket you're playing with 120V and ground on wires no bigger than 12 gauge, in a fairly well controlled environment. ... "Applied Control Theory for Embedded Systems" gives you just what it says. ...
    (sci.electronics.basics)
  • Re: OT: Well pump wiring
    ... add-on for most modern panels that slips over the breaker handle to ... prongs coming out of it that bridge some connectors inside the control box. ... That's what I would consider to be the "lockout" for the pump, ... The pressure switch is "pilot duty" and there's ...
    (rec.crafts.metalworking)
  • Power monitoring; ws Re: one wire sensors
    ... conditioning, power supply and analog, digital, and 1-wire connectivity ... each branch breaker at a home's breaker box? ... monitoring and control functions I have developed. ... " SAVOY AUTOMATION AND CUTLER-HAMMER POISED TO REVOLUTIONIZE ENERGY ...
    (comp.home.automation)