Small Well Pump Wiring

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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
I wanted to get some input from the members here that have experience in wiring small residential wells. Most of the projects I work on are served by municipal water systems but occasionally I work on jobs in the hills that require wells. On these projects we usually run a feeder to a small panel near the well and the well/pump contractor takes it from there.

I?m working on a project now that is totally off the grid (no electric, gas, phone or water services). We pulled a feed and installed a panel next to the well along with 3 GFCI protected receptacles for the UV filters. The plumbing contractor has a pump person on staff who is supposed to complete the rest of the wiring. One of the regular plumbers visited the job site a couple of weeks ago and installed the UV filters in the 3 storage tanks but didn?t install the float switches or do any of the wiring for the well pump. The Forman for the GC called the plumbing contractor and was told that his pump guy is very busy so just have the electrician finish the wiring.

I talked to the owner of the plumbing contractor and told him I at least want them to install the floats. I also asked if they were going to supply any type of pump controller or contactor. He said that no additional equipment was required since the contactor was part of the small pump control box that was already connected directly to the cable coming from the pump.

From what I have seen this box is usually just a capacitor for the pump. I went up the hill and took a look and sure enough the box is just a small relay and capacitor. It has 4 terminals that connect directly to the well pump cable and 2 terminals (L1 & L2) for the supply. The relay is just used to control the capacitor.

According to the label placed on the ?capacitor box? the FLA of the well pump is 7.8 amps @ 240 volts. I have no idea what the switch rating is of typical floats but is it normal to just have them switch the well pump motor load off directly without any type of contactor? Also do small well pumps typically require any type of external overload protection? I?m thinking even if the floats can handle the 8 amp motor load it would be better to have them control a contactor that controls the pump. If the pump requires external overload protection I would need to use a magnetic starter instead of a simple contactor. How do you guys normally deal with this type of installation?
 
Float switches are used frequently for small pumps. Especially when used to fill tanks. The box that comes with pumps frequently was not the controller in the past. It had potential relays, a capacitor and a thermal overload but did not start/stop the well. That was the pressure/float switch duty.
 
Most of the wells I see are pressure switch controlled but the few well float switches I have
seen were rated around 1 HP and 15 amps.
 
curt swartz said:
According to the label placed on the ?capacitor box? the FLA of the well pump is 7.8 amps @ 240 volts. I have no idea what the switch rating is of typical floats but is it normal to just have them switch the well pump motor load off directly without any type of contactor?
Click to expand...
Most float switches are 15A so they can handle the load.

Also do small well pumps typically require any type of external overload protection?
Click to expand...
No.

I?m thinking even if the floats can handle the 8 amp motor load it would be better to have them control a contactor that controls the pump. If the pump requires external overload protection I would need to use a magnetic starter instead of a simple contactor. How do you guys normally deal with this type of installation?
Click to expand...
We make well control boxes in our shop. It has a small 24V transformer and a contactor with a 24V coil so the floats or a pressure switch runs off of 24V. If it is a deep well or a long run from the house to the well a rectifier gets added and a DC contactor is used so there is no capacitance holding the contactor in once the switch is opened.

Even if I don't use one of our boxes I'll often use a contactor and let the floats control the coil the theory being the contacts in the floats will last longer.
 
augie47 said:
Most of the wells I see are pressure switch controlled but the few well float switches I have
seen were rated around 1 HP and 15 amps.
Click to expand...
You can even have both at the same time, sort of......It is common here to have a well that can't keep up with the demand so a cistern is installed. The well pump is controlled by float switches in the cistern and the cistern pump is controlled by a pressure switch.
 
Thanks for the replies. It sounds like the owner of the plumbing company was correct in stating that no other controls are required. I kind of like the idea of adding a contactor to limit the load on the float switch and it would also break both legs going to the motor instead of just one. Considering the electrical for this house is approaching $500,000 I don?t think a $35 contactor will break the bank.


Dave, you mention the capacitance of the wire holding the contactor in brings up a second question. The well, and holding tanks are right next to each other so the wiring between them is very short so don?t foresee any issues. There is also going to be a second float switch that needs to be connected to a normally open solenoid valve in the main house. This second float switch needs to supply power to the valve if the tank water gets down to about 66% so the domestic water shuts down. The remainder of the water must only be available for the fire sprinklers. The distance between the well and main house is about 1,000?. I was wondering if having 1,000? of wire would cause the solenoid valve to open since the load is so small. I was thinking maybe putting some kind of dummy load in parallel with the solenoid valve would be necessary or a good idea. Any thoughts
 
curt swartz said:
Thanks for the replies. It sounds like the owner of the plumbing company was correct in stating that no other controls are required. I kind of like the idea of adding a contactor to limit the load on the float switch and it would also break both legs going to the motor instead of just one. Considering the electrical for this house is approaching $500,000 I don?t think a $35 contactor will break the bank.


Dave, you mention the capacitance of the wire holding the contactor in brings up a second question. The well, and holding tanks are right next to each other so the wiring between them is very short so don?t foresee any issues. There is also going to be a second float switch that needs to be connected to a normally open solenoid valve in the main house. This second float switch needs to supply power to the valve if the tank water gets down to about 66% so the domestic water shuts down. The remainder of the water must only be available for the fire sprinklers. The distance between the well and main house is about 1,000?. I was wondering if having 1,000? of wire would cause the solenoid valve to open since the load is so small. I was thinking maybe putting some kind of dummy load in parallel with the solenoid valve would be necessary or a good idea. Any thoughts
Click to expand...
Shouldn't be a problem since the valve is normally open but it would be a nice design to put an indicator light alerting the home owner that the valve is closed......presto! You change your dummy load to a smart one and brag on yourself to the HO telling him how cool you set him up so he can easily see when his water is low.
 
curt swartz said:
Thanks for the replies. It sounds like the owner of the plumbing company was correct in stating that no other controls are required. I kind of like the idea of adding a contactor to limit the load on the float switch and it would also break both legs going to the motor instead of just one. Considering the electrical for this house is approaching $500,000 I don?t think a $35 contactor will break the bank.
Click to expand...

I think you are overthinking this. Adding a contactor only adds more equipment to fail.

If the float switch is rated for the pump I would just use it and there is no reason to break both lines.

Any small wells I have wired or seen switched direct, no contactor.
 
ActionDave said:
Shouldn't be a problem since the valve is normally open but it would be a nice design to put an indicator light alerting the home owner that the valve is closed......presto! You change your dummy load to a smart one and brag on yourself to the HO telling him how cool you set him up so he can easily see when his water is low.
Click to expand...

That is actually what I was thinking about doing. The valve is in a large mechanical room. I could a red incicator light which would add load to the the circuit and let the homeowner know why their water is off.
 
iwire said:
I think you are overthinking this. Adding a contactor only adds more equipment to fail.

If the float switch is rated for the pump I would just use it and there is no reason to break both lines.

Any small wells I have wired or seen switched direct, no contactor.
Click to expand...

That sounds like me! :)

I don't have the floats to look at the rating so wasn't sure they could handle the load. Since you guys say they should be able to handle the motor load I will probably just go that way.

The GC's Foreman wants the pump connected ASAP. He is getting tired of dragging a 300 pound generator up the hill to refill the tanks. Without the floats he can just flip the breaker on for a few hours. The plumber can install the floats at later time.
 
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