On Fri, 14 Aug 2020 10:56:02 -0700 (PDT), "
wrote:


Water well pressure switches should always be placed as close to the
pressure tank as possible. Within 1 foot is best. Nearly 300 feet away
at the well head would be a bad idea.

That posits a conventional pressure switch. If I understand correctly, your well is some distance from your house, and the tank is some distance from your well - by your description, some 300 feet. You also state that the pressure switch is 100% mechanical in action, and capable of switching the 240 Volts to the pump. You intend to re-purpose that switch to activate a contactor switching pump power from the house - because there is an emergency generator at the house. So, being a bear of little brain, I am trying to understand how you intend to do this:

a) Take power from the line at the pump and send it to the Pressure Switch, then back to the contactor to activate it. Makes sense if you have a ground and a neutral in the run between the pressure switch and the pump and the same to the well-head from the house - 240V 4-wire (hot/hot/neutral/ground) allowing you to use 120V as the coil voltage. This makes all voltage to the pump and its controls originate at the house. If carefully managed, and all the conductors are the correct gauge, this will even meet codes. However, you need to verify that the pressure switch is properly rated (most are).

b) Use the existing power from the shed to activate the coil - problematic as you have two different power-sources in the same panel - able to be managed, but code compliance, again, is problematic. And, if the power goes out, so does the well as there is no power to run the coil.

I sent you to an industrial pressure switch sophisticated enough to account for the lag due to the distance from the tank. As the tank is (apparently) doing its job as far as house-pressure is concerned, it can continue to serve with a distant pressure switch if that switch can be programmed to include the lag. This keeps all your controls in one place, served by one source, with fewer failure opportunities. All good when a critical function is being covered.

We have a similar set-up here for the diesel fire-pumps and generators scattered across 1,200,000 square feet of building covering a city-block. There is a Veeder-Root tank monitor system some 80 feet away from the three x 1,000 gallon underground tanks under the sidewalk outside. This device monitors tank levels, fuel temperature, moisture content and so forth. There are three (3) local pumps on a lead-lag system that feed the day-tanks located at each fire pump and/or generator (total of seven (7)). These are activated as-needed (1/2/3, then 2/3/1, then 3/1/2) as needed - any two can keep up with all seven locations if needed. But, the float-switches in the day-tanks are as much as one flat block and 23 floors away from the USTs and pumps. And, all of these things "talk" to the Veeder-Root, which prints out a status once-per-day, and also a report every time a fill-pump is activated. Point being that the controls are nowhere near the tanks.


Peter Wieck
Melrose Park, PA
The pressure switch at the tank is the typical snap action type
found on every well and air compressor I have seen.
Even though I have 4 wires coming from the shop and going to the
well I will only be using two of them.
I have found several 240 volt coil motor start contactors that are
suitable for switching power to the well.
The power from the house will power both the contactor coil and and
the well pump. The ground and neutral from the shop will not be used
because code says the only ground and neutral for the pump house must
come from a single source. So the generator sub panel is connected to
the main panel ground and no other. The box at the well head will
still have a floating ground and floating neutral, just like the gen.
sub panel, but instead of getting the neutral and ground from the shop
will now get them from the house.
Is there any reason that a 120 volt coil contactor should be used
instead of a 240 volt coil? Since I did run 4 wires from the house as
I did from the shop I could use a 120 volt coil by using the neutral,
but I don't see the point.
There is no reason to relocate the pressure switch as near as I can
tell. The current pressure switch is inexpensive, reliable, and
available 7 days a week even here on the island. Besides, I already
have an extra new one sitting on the shelf. And I already have wires
in the ground going to the switch, so why not use them? They will just
be switching less current. And from what I can tell, the snap action
type of action used in these switches is so the contacts always make
good contact because they slam together. They even slam right through
spiders and beetles. I dunno why the bugs like to hang out on the
switch contacts. Mebbe it's done on a dare.
Thanks,
Eric