Water pump timer control

Thread Starter

bajarefugee

Joined Jan 18, 2021
4
Bear with me please.
We are an HOA in Baja Mexico.
We have a well with a 3 HP 220v pump that fills a water tank, float switch controlled, and have gone through three pumps, with repairs, over the last 8 years.

We identified failure due to 2 causes. Brown out conditions (very common here) and excess heat in the pump house during summer.

We are installing High/Low voltage and load protection.

But to deal with high temperature events we want to add a timer to the float switch and only run the pump at night during the high heat months.

The Over/under load device has a timer but it is AC powered. That would throw the timer off during power outages.

I am wanting to add a DC Relay/Timer to the float switch circuit to "jump" it during the day and enable it at night.
It would be powered by a car battery which would be connected to a float charger.
Power is usually out no more than 36 hours so a good battery should not drain.

Is this the simplest solution?

If so how would I wire this timer relay to the float switch?

What should its amperage rating be?

Any other approaches?

Gracias!
 

Tonyr1084

Joined Sep 24, 2015
6,079
Any other approaches?
Welcome to AAC.

Using a photocell you can turn the pump system on at sunset and off at sunrise. Same as you would with a porch light.

As for power failures - if one can last for 36 hours, how many of those hours do you need to run the pump? What voltage is the pump? What horse power or amperage is the pump?

Every year I use a plug in timer to control Christmas lights. For the rest of the year it sits in a box. It has its own internal battery and keeps time while not plugged in. IF it's unplugged too long the battery may drain and lose time. If you're only losing power for short periods of time during the year - say as you have 36 hours, that timer will have no problem keeping time. You can also use that to run the pump at night. Given that the pump doesn't draw more power than the timer switch can handle.

One thing that came to my mind when you were talking about failures of the pump motor - it could be short cycling, meaning it's ON - OFF - ON - OFF - ON - OFF in short cycles like every 2 to 5 minutes. This could be caused by an improperly installed float switch. In most systems of this nature the switch will turn the pump on when the water gets low. Say, nearly empty. But that's adjustable. Then the pump runs until the tank is near full, then shuts off. That too is adjustable.

But to get good answers you're going to need to provide details such as motor voltage and amperage. Horse power may be helpful too. Also, to satisfy my concern about an improper float switch setup, please provide details on that as well. How much does the water level drop before the pump comes on and how long does it take to fill the tank. All pertinent information.
 

Thread Starter

bajarefugee

Joined Jan 18, 2021
4
Thanks for this reply!
I believe we are using the low voltage circuit on the float switch to control the high voltage relay.
So a photocell would work perfectly in the summer.

Our float switch was professionally installed and the water level drops 3 feet before turning the pump on.
It takes 30 minutes to fill (big tank).

The pump is 220v / 3 HP, single phase. I am not sure of the amperage.
 

sghioto

Joined Dec 31, 2017
2,373
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Tonyr1084

Joined Sep 24, 2015
6,079
OK, so you're switching 3Ø (3 phase). When you lose power you're going to need a serious inverter, one with 3Ø and batteries big enough to run the pump long enough to keep water topped off. That's a pretty big order. You might be better off with a generator to run the pump. 3HP - that's no light weight motor.
 

Tonyr1084

Joined Sep 24, 2015
6,079
Sorry. I thought he said:
I am wanting to add a DC Relay/Timer to the float switch circuit to "jump" it during the day and enable it at night.
It would be powered by a car battery which would be connected to a float charger.
Power is usually out no more than 36 hours so a good battery should not drain. (underline by TonyR1084)
Overall, the three things I got from the question is "Pump motors failing due to brown-outs"; "Pump motors failing due to excess heat"; "Powering pump motor during power failures".

I'm not 100% on powering the pump during power failures. Maybe the tank can hold enough water to make it through a few days without running the pump. Perhaps that's another "good" question to ask. How many gallons does the tank hold and how much demand is there on the water tank?
 
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Thread Starter

bajarefugee

Joined Jan 18, 2021
4
Sorry, I should have addressed power outages more clearly. We do not need to power the pump during power outages. In the summer there are only two residents here. Our tank, with the tinacos in each home, holds enough water to last them a week.
 
Why don't you get a battery backed up astronomic timer. They might use a coin cell.

Astronomic means it calculates sunrise and sunset. You generally can do stuff like turn off (disable) 3 hours after sunrise and enable 3 hours after sunset. These times are computed.

For relibility you might consider two pumps that alternate pumping plus your undervoltage lockout. the undervoltage lockout should have a delay for atarting back up.
 

MisterBill2

Joined Jan 23, 2018
9,034
The photoswitch would not have to be one of those open modules. Since the motor is switched by a motor-starter contactor it would be rather simple to use a 3 wire photoswitch to enable power to the float switch. The reason that I suggest the 3-wire type is because the two wire type could have a random delay and not change state until the float switch was demanding that the pump run.
An alternate approach would be to have a thermostat in the pump house to disable the pump when the inside became too hot. The benefit being that it would not need to be disabled during the cooler months.
 

MisterBill2

Joined Jan 23, 2018
9,034
In this case you really only need a set of contacts in series with the float switch.
Certainly correct. But many thermostats are only rated for half an amp at 24 volts. The coil in the motor control contactor probably is mains powered, 120 vts AC, and probably draws an amp. Much less than the motor power but much more than for a gas furnace control.
So my point is that the contact rating of the thermostat must be kept in mind when making the selection. And since the motor starter is already in place, it's requirements should already be understood.
 
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MisterBill2

Joined Jan 23, 2018
9,034
I'm leaning more to a relay module that is controlled by temperature.
"Relay Module" is a very broad term, and not very well defined.
Given that the application is for an installation that feeds a number of homes, it needs to be rather rugged and already enclosed so that it can survive in a pump-house environment. That is the point that I was making.
Probably Automation Direct would have a suitable device at the best price. Allen Bradley would also have a suitable device but at a much higher price.
 
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