Hello, I have a two wire well pump out at a cabin. We recently put in a new pressure tank with a new pressure switch. When it was powered up, the pressure switch keeps turning on and off rapidly. Being its only a two wire motor could the biac switch be bad or maybe the motor itself. When they hooked up the pressure switch, the 120v power source was hooked up backwards and after the breaker tripped they reversed it and it held. I dont know if this damaged the pressure switch but that could be part of the problem. I wasn’t there when all of this was done but I’m supposed to head there sometime and check it out so I’m wondering what to look for. I dont think hooking up a pressure switch with the leads reversed would cause the breaker to trip but I don’t know what exactly they did. Any help would be of great help with this mess. What sucks is this place is 2 hours away from home and in an isolated area.
Not a lot of info to go on here but I can try to help you out.
Your instinct is correct the wires being reversed should not create that issue.
Wiring it backwards wouldn’t damage the pressure switch, but it turning off rapid fire would. and damage wound be plainly viable on the contacts, just see if they look charred
Put in a new pressure tank and switch? Did it have these things before? Was the pump running correctly prior to any change? If the motor was wired for 120 I wouldn’t expect any damage from the polarization being reversed it should run either way.
What is the deal with the pump? What type of pump? I’m going to assume the pump is in the house(not in the well) was it wired for 110v? The default on the motors is 220v you have to change a jumper for them to run on 110v. Is it a shallow well pump, ie one pipe going to the well and one to the house or a deep well jet 2 pipes going to the well and one to the house?
Where is the pressure switch tied into, tank tee, pump housing, somewhere else?
Well data?
make and model of pump would help greatly in leading people to help you.
the pressure switch could be in the wrong location on the pump.
what do you mean by being hooked up backwards?
was the pump primed and started according to instructions?
more details would help people make sense of this.
I am not a plumber, but I once had a pump rapidly turn off and on and that was because the air cushion in the pressure tank was gone. Bleeding the lines and restoring the air cushion solved the problem, and using a rubber bladder-type tank instead of an air cushion prevented it from recurring.
First thing to figure out why was the pump turning on and off rapidaly?
Was the pressure in the system increasing to the set point before the pump shut off? And how much did the pressure drop before restarting.
If the pressure difference is low then I would question the switch or wiring.
If you are getting a good shut off pressure with proper differential before restarting the the system is in question. That is the pump starts the pressure increases then shuts off. Then the pressure rapidaly drops and the pump restarts.
Things to check: expansion tank, check of foot valve.
A hole in the foot valve caused my pump to run continuously.
Hard to tell for sure at a distance, but it sounds like what Musicat suggested. The condition is known as “waterlogged”. Most pressure tanks have an ordinary air filler valve (just like the ones on tires) located somewhere on the tank. Drain about half the water out of the tank and fill the space with an air compressor to about 20 PSI. (I’m guessing at the correct pressure; check the manual). If this is indeed the problem, it should put things right.
SS
new pressure tanks will have an air bladder inside. if the bladder has the proper pressure then you are good. the air that gives the pressure and the water don’t mix. good for a long time.
old pressure tanks had no barrier between the air and water, they do get waterlogged. the air would gradually dissolve into the water and the air would disappear. a symptom of this would having low water pressure and having the pump going on and off frequently while using the water. to remedy you would turn off the pump off and drain liquid from the tank (have the air valve open) and pressurize.
It’s hard to understand that, if it’s normal 120V AC power. AC means alternating current, so the electrons alternate moving back & forth either direction along the wires – unlike DC or batteries, there is no specific plus and minus wire.
Electrical wiring has a hot (black) and a neutral (white) wire, but that is mainly a safety issue – the neutral wire is also connected to ground. Most electrical appliances will work fine with the wires reversed; it’s just more of a safety risk. For example, on light sockets, the neutral wire is connected to the outside screw of the socket, while the hot wire goes to the small button in the bottom center of the socket – there’s less chance of someone touching that live part accidentally.
I had the same problem with my old well. Someone had to go into “the pit” every 3 months or so and bleed the tank. It was a real hassle because it was in a pit lined with concrete blocks out in the yard. Then one year a groundhog decided it would make a dandy groundhog house and it scooped about 3 feet of sand into the bottom of the pit. Thank goodness the pump finally crapped out completely and I had to have a new well dug because the old one wasn’t in compliance.
I don’t know the make and model of the pump…its not in the house. As far as the well its a 220v well. The 120 was the pressure switch, but I don’t think most pressure switches require power to them, other than the power they are controlling. I think I’ll run out and take a look and see what kind of info I can get. Well was operating fine before they replaced the pressure tank…the switch isn’t turning on for a while then off…its going on/off/on/off with no more than a second in between. So if that helps at all let me know what you guys think, otherwise I will get back to this posting this weekend. Thanks!
The pressure switch turns the pump on and off. In every pump I’ve seen, it switches the pump on and off with the voltage supplied it, rather than a relay that switches another voltage.
And upon review, I see that it is “two wire”. That is 120v.
220V is 2 wire with two hot wires. 120V is 2 wire with a hot and a neutral. 3 wires could be 220V/120V or 2 120V or other things.
need more details.
Two “hot” wires and ground makes three. 
I’ve not seen a 220v device that works with two wires.
a grounding wire doesn’t get included when talking wire count most often, it is there for the technical aspect of volume. wire count are current conducting wires. grounding wires aren’t required for operation (by far most of the time) just for safety. a 220V motor will operate with only two hot wires.
Do you have a cite? I’ve never seen that.
Thanks.
Sorry I do not have a sight just the books in the bookcase and years of experience. A ground wire should not carry any current and should not be a part of the circuit. Either on a 120, 208, 220, or a 277 vac motor circuit.
I’ll confirm John’s statement that a ground is not necessary for operation. I’ve handled hundreds of 220v motors that did not use grounds. It wasn’t till about 15 years ago that submersible pumps required a ground wire. Many of the pumps prior to then where put in without a ground wire and wires between the house and well don’t have a ground wire. When changing out those pumps sometimes it isn’t practical to run new wiring between the house and the well so the ground from the pump is only bolted to the well so even on a new pump you’d only have 2 wires in the house.
Counting wires is never a good plan for determining voltage. Read motor plates and use volt meters. Some common examples.
2 wires can be
120v no ground
220v no ground
277v no ground
480v no ground
3 wires can be
120v w/ground
220v w/ground
220v w/starting coil no ground
220v w/ground
277v w/ground
480v w/ground
480v w/starting coil no ground etc
Then you have a number of 4 wire configurations.
I stand corrected, but you don’t ground the case of the motor?
Yes you ground the non current carring metal parts of the motor, that way if there is any leakage current it will have a safe path and not through someone touching the motor.