Half-switching a well pump box

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George Stolz

George Stolz

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Windsor, CO NEC: 2017
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Hospital Master Electrician
I am going to be trimming a SIP-home with a standalone PV system that I roughed a few months ago. Now I have a little question:

The homeowner wants an override for the well pump, so that he can manually turn on the well pump during the day to fill his cistern, so that he can "make hay while the sun is shining," to use his metaphor.
:)

Does
 
Re: Half-switching a well pump box

George call me stupid but won't the float switch fill the tank whenever it is low?

How about you just shut the unit down at night?
 
Re: Half-switching a well pump box

...won't the float switch fill the tank whenever it is low?
Click to expand...
Probably whenever it is very low.

How about you just shut the unit down at night?
Click to expand...
By what, photoeye? He would balk at such a phantom load.

Manually? If he forgets for a few weeks, then it could run dry and burn up the secondary (post-cistern to pressure tank) pump.
Jim wrote:
If it has a float switch what good will it do to bypass it? It will not fill any faster by bypassing it
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He's not going for "faster." He's going for "more opportune timing."

By choosing when the tank fills, he can save his batteries. The solar panels will directly power the well pump (more or less), saving wear on his batteries.

Some PV folks sell power back to the utility that exceeds what they can store. This guy has no utility - power generated by his panels to full batteries would be otherwise wasted, he is going to put it to use topping off his cistern.

Would having one leg energized damage the well controller?

I know I would have to use a threeway rated for 240 (ie 277), but it seems like the most efficient means to the end.

I wouldn't use the second set of contacts in the float switch, if there are any. The black from the panel would run from the panel, unswitched through the 3-way's box, and then proceed out to the well pump. The float switch would look like a farmer (dead-end) switch from it's perspective
 
Re: Half-switching a well pump box

If the only objective is to bypass the float switch why not just connect a singe pole switch in parallel with the float? I don?t understand what the a 3-way switch does for you.
 
Re: Half-switching a well pump box

George

I am confused about your question. If you have a well control box doesn't it have a relay or contactor in it that makes and breaks the power to the cap. and motor?

Most I have worked on did. :)
 
Re: Half-switching a well pump box

I just found this image here.
controlbox.gif

This represents the standard Franklin control box I am accustomed to seeing. As the pump installer is the same guy who did my personal home (by coincidence), I can assume he still installs the same equipment. I haven't seen it yet.

If the schematic is an accurate one for my scenario, then my switched red leg would be best connected to "L1", right?

(It doesn't really matter either way, does it?)

Edit: meant "L1"

[ October 02, 2005, 03:12 PM: Message edited by: georgestolz ]
 
Re: Half-switching a well pump box

George,

The way I understand the well start box is this:

Upon energization the motor looks pretty much like a short and the voltage across the motor sags. In order to get good starting torque a "moving" magnetic field is created from single phase by energizing a start winding through a capacitor. As the motor approaches speed, the back emf of the run windings increases and the voltage sag lessens. The relay responds to the voltage increasing back to the voltage between L1 and L2, and at a near 100% percentage of that voltage drops out, disconnecting the capacitor and, in turn, the start winding.

That said, George, think of this: The float switch is breaking only one side of the L1-L2 circuit already, leaving the start box always energized by the line that doesn't go through the float switch.

What about adding the single pole bypass, as Curt suggested, in series with a second float switch used as a high level limit?

That way, if the tank tops off, the pump stops drawing energy.

Also, since this is for "making hay while the sun shines", I'd also add a photoeye defeat in case clouds come in or dark arrives before the manual ON is turned off or they just plain forget and leave it running after the PV output drops off.
 
Re: Half-switching a well pump box

Originally posted by al hildenbrand:
That said, George, think of this: The float switch is breaking only one side of the L1-L2 circuit already, leaving the start box always energized by the line that doesn't go through the float switch.
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Exactly. I am not sure if this will damage the capacitor, or the relay. That's my primary question. :)

Question 2 would be, if answer to #1 is 'yes', then would connecting the switched leg to "L1", (thus going through the motor before coming to the dead end of the start box) would the effect be lessened or eliminated?

What about adding the single pole bypass, as Curt suggested, in series with a second float switch used as a high level limit?
Click to expand...
That's an excellent suggestion. I wonder if it's already setup as such, it could very well be, I haven't seen it yet.

Also, since this is for "making hay while the sun shines", I'd also add a photoeye defeat in case clouds come in or dark arrives before the manual ON is turned off or they just plain forget and leave it running after the PV output drops off.
Click to expand...
Two problems with that: The guy is terrified (to such extent I could write volumes about) of phantom loads. The photoeye has a phantom load, doesn't it? Doesn't it draw a small amount of current when operating (but open)?

Edit - Problem 2: The PV output would drop off well before any photoeye I am aware of would act - If the solar panels are shaded by over 80% (or over 50%, I forget), then they lose almost all of their production. So installing a photoeye to counter this effect would be futile.

All things being equal, I think I might just go ahead and get a double throw switch to bypass the low float sensor. Sometimes being clever must give way to caution. :)

[ October 02, 2005, 07:11 PM: Message edited by: georgestolz ]
 
Re: Half-switching a well pump box

George,

It would be nice to be able to tap off the PV power to energize a relay that would automaticly switch the pump on/off as long as the PV system was putting out power.
 
Re: Half-switching a well pump box

A while ago I looked into PV systems and quickly found that they are sticklers for getting rid of unnecessary power consumption. It is a different way of thinking, forget about relays, photo eyes, electronics etc.

The cost per watt of the panels is so great anything you can do to reduce power consumption must be done. They even sell low current appliances for these homes.

It sounds like this is the way to go.

What about adding the single pole bypass, as Curt suggested, in series with a second float switch used as a high level limit?
Click to expand...
No additional power draw and if they forget no wasted power flooding the area with water.
 
Re: Half-switching a well pump box

Originally posted by iwire:
It is a different way of thinking, forget about relays, photo eyes, electronics etc.
Click to expand...
One of the eccentricities of this home is, every GFI in it is switched to avoid the phantom loads. I wrote about it at the rough.
It sounds like this is the way to go.

What about adding the single pole bypass, as Curt suggested, in series with a second float switch used as a high level limit?
Click to expand...
No additional power draw and if they forget no wasted power flooding the area with water.
Click to expand...
A single pole bypass?

How would that be different than the switching I drew in the first picture? :confused:

[ October 02, 2005, 09:29 PM: Message edited by: georgestolz ]
 
Re: Half-switching a well pump box

George,

Choose a spring wound 12 hour timer switch as the bypass switch. Zero phantom load. Operator control based on known weather conditions and how much of the day is left.

And about this:
Exactly. I am not sure if this will damage the capacitor, or the relay. That's my primary question.
Click to expand...
My point, simply, is that, under normal operation, without any single pole control switches, the capacitor-start winding is controlled by that single pole voltage relay. Under normal operation, when ever the pump is running, the capacitor-start winding is always energized on one end and open on the other.
 
Re: Half-switching a well pump box

My point, simply, is that, under normal operation, without any single pole control switches, the capacitor-start winding is controlled by that single pole voltage relay. Under normal operation, when ever the pump is running, the capacitor-start winding is always energized on one end and open on the other.
Click to expand...
So, simpler, there wouldn't be a problem?

I think I've had a long day. I'm feeling dumber as time rolls by... :p
Edit: As in, I needed sleep. You're clear as a bell, I was tired at the time. 10/03

[ October 04, 2005, 12:14 AM: Message edited by: georgestolz ]
 
Re: Half-switching a well pump box

Everybody should just move to someplace where there is public water. :D Sorry, I'm just kidding around, we have a lot of people on wells/cisterns around here too. This is a bit off the subject, but do you ever work in Cheyenne, WY George? I know you live in northern Colorado.
 
Re: Half-switching a well pump box

Sure did. Got stuck there for a few months. The home of the school of excessive bonding, where you have to bond two copper manifolds above the hot water heater together in a PEX system. :D

Why, you in Cheyenne?
 
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