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Is my submersible pump nearly finished?
I need some help and advice with troubleshooting a water supply problem.
Background: approximately 270 foot drilled well. Submersible pump replaced about eight years ago. Original pump was about 25 years old. We have a standard submersible well pump system including new pressure switch with low-pressure cutoff, 20-gallon pressure tank, and check valve inside house. Not sure of the brand or details of the submersible pump or if there are other check valves in the system. Pump is wired for 240V. Location is New Hampshire.
Starting about a month ago, we started to lose water supply. Initial troubleshooting was hampered by a failed pressure gauge, so the gauge was replaced and, because it was an inexpensive first step and the age and condition of the original was unknown, the pressure switch was also replaced.
Here is what's happening: when using water, the system will draw down to the 30 PSI cut-on setting and the pump will start. However, before reaching the 50 PSI cut-off, the pump will stop pumping (it runs for about 40 seconds). After about two minutes, the pump will start again and will usually reach the cut-off pressure. Sometimes it takes multiple cycles like this to reach cut-off if there's been a large demand for water, like to fill the washing machine. With each subsequent cycle, the pump runs for a little less time and stays off a little longer.
It sounds to me like a failing pump but I'd like other opinions before I replace it. Could something else be failing? If it's the pump, why has it not failed completely? I've cannot find any other descriptions of a similar failure scenario online.
I've made my situation a bit more troublesome by installing a pressure switch with a low pressure cutoff. Now it's possible for the system to occasionally draw down to the point that the switch needs to be reset.
Any opinions or advice are welcome. Since we're not totally without domestic water, I'm waiting for the weather to warm up a bit before I consider pulling up the pump myself just to see what I can see and get some more details about the existing pump.
Thanks for reading.
-Dan Hall
Sounds like the overheat switch inside the pump is tripping. They reset after a few minutes typically.
Until you find the cause, try turning down the pressure, perhaps 25 to 40.
A quick diagnostic is to check the running amps and compare it to the motor specs. Then check the wires for leakage to ground. Sounds like the pump is getting tired.
Do a search for Franklin electrics AIM manual. It explains all.
http://www.franklinelectric.com.au/aim.aspx
Does the pump have separate start and run wiring with a control box topside or just a 2-wire? BV probably pegged it right that the thermal overload on the motor may be tripping. There is always the possibility that a high resistance contact or splice is to blame.
If it has a control box, try a new capacitor.
A bad cap. will cause the same symptoms you describe.
"I shall never surrender or retreat" -Col. William Travis
You didn't say- does the pressure switch click on and off when the pump cycles on and off, or is it that the pressure switch definitely stays on while the pump seems to stop and then restart?
The difference will be a completely different diagnosis.
Thanks all for all the helpful and informative responses!
ballvalve, an overheat switch tripping within the pump sounds logical. As I mentioned, the pump stays on for a shorter time and off for a longer time when there’s more demand, so it makes sense. I don’t know what the motor specs are until I pull the pump, but I’ll plan on measuring the resistance of the two wires to ground. I'll also lower the pressure tomorrow to ~22-42 (the differential on the switch I have is fixed at 20) to hopefully buy some more time with the pump.
FYI, for a few years of the pump’s fairly short life so far, it’s been used to do a lot of lawn and garden watering, so it may have been overstressed.
No LLigetfa and Waterwelldude, the pump doesn’t have a control box; just a 2-wire pump with pressure switch. In fact, exactly two wires to the pressure switch and two from there out through the basement wall. Would that mean the pump’s probably got a separate ground wire within and to the casing? I guess I’ll know when I look down there.
And cacher_chick, that’s a great question. I do not believe the pressure switch is toggling off when the pump stops before reaching cut-off, but I’ll verify tomorrow.
I agree that it sounds like an overloading pump. FWIW our office is only 2 towns from Raymond.
Okay, I've got some measurements.
The resistance from each pump load wire to ground is about 3.8M Ohms. The resistance across the load wires is about 6 Ohms when the pump is "online" and from 7M Ohms rising to 10M Ohms when the pump has seemingly tripped its thermal protection switch.
When the pump stops before reaching the cut-off pressure, the pressure switch contacts are still closed.
More evidence pointing to a tired pump, I'd say. Because if there was a high resistance contact or splice in the load wiring, wouldn't the circuit breaker trip due to overcurrent? What would cause the pump to thermally cutout - worn pump bearings?
How can I measure the load current? Do I need an clamp-on probe for my DMM?
Thanks again for any advice offered. I think I'm going to start educating myself on replacement submersible pumps and loosen my wallet. ;-)
A clamp-on current meter is the right tool-I don't leave home without one. In lieu of that 2 "tricks":
A) see if the cellar lights brighten when the OL opens
B) you can watch the electric meter but it can be tricky to coordinate that with the pump operation
You can test, test, and test some more but it's a 2 wire pump so..... It's either the pump or your wire to the pump and in either case the pump needs to come out of the hole.
A high resistance would act to limit current. 270 feet of wire down the well plus whatever to the house will also act as a current limiter.Originally Posted by danielrhall
I mentioned the possibility after my neighbor who BTW was an electrician, misdiagnosed his pump problem that was drawing high current. In his case one leg was drawing twice the current of the other leg, so half the amps were going to ground. He thought the motor winding was shorting to ground but it turned out to be a bad heat shrink job leaking to ground. Lucky for him it was a cheap repair bill ($10 for a splice kit).
A clamp-on is what you need and you need to test both sides individually.
I found the receipt for the pump.
The invoice says "5GS05" which seems to be a Goulds 5 GPM submersible. Since it's a 2-wire pump, based on their literature, it is likely a 5GS05422 which is a Goulds GS Stainless Steel Series, 4", 2 Wire, 5GPM, 1/2HP, 230V.
Bought on 05/24/04 from a local well and pump company, who installed it. Also 260' of 12-wire. Paid a lot for both! ;-)
It's rated at 3.7 amps, so perhaps I can measure the series current with my DMM for a short period of time. But you're right Tom Sawyer, it's coming out of the hole regardless.
Thanks again to all for the information. I'm way more educated on this subject than I was just 24 hours ago. And speaking of... if I'm going to insist on continuing to water the lawn and garden with my current system, is a cycle stop valve a wise investment?
-Dan
According to the specs from Goulds, a 1/2 HP 2-wire, 240V should draw 6 amps starting, and 5 amps continuous. I have the 10GS05 with separate start wire and control box.
Pumps are made for 24/7 continuous running. It is cycling on and off that kills them. Seven years is the average life of a submersible pump when used with a “properly sized pressure tank”, and allowed to cycle on and off. Your watering habits have been predicted in advance. Pump manufacturers know just how many times you will cycle your pump in seven years, and they put just enough quality into the pump to make it only last seven years.
This tells me that you are use to the pump cycling on and off when you use water. And like most people you thought this was the way a pump should normally be working. Some people even tell me they thought the pump needed to rest part of the time.
Without a CSV, you need to run enough water to keep the pump from cycling, EVERYTIME you run water. Probably means you need to run 3 or 4 sprinklers at a time instead of 1 or 2. Eliminate cycling when watering the garden or yard, and you will triple the life of your pump. A CSV will allow you to run 1 sprinkler at a time if you want without cycling the pump to death. Since your pump was prematurely destroyed by cycling, a CSV would be a no-brainer. A CSV just means you never need to worry if you have enough sprinklers running to prevent destroying the pump.
I have heard this 7 year average several times in several other places but I don't believe it. I've been servicing and installing submersible pumps for over 30 years now and we keep pretty good records. I would say the average is closer to 15 years with many, including my own, having been down the hole for over 25 years. I'd like to hear from other pump tech's here and see what they think average life is.
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