Water Pressure Pump Switch contact damage

[radioFlash]

The water pressure pump switch on my water well is dying after about a year or so of service. The switch turns on when the pressure drops below 40 PSI and turns off when it reaches 60 PSI. The contacts are getting damaged from arcing when the switch turns on and off. This results in the switch either failing to engage when the pressure drops or getting stuck on when the contacts weld themselves together.

I'd rather not have to replace the switch every year. What's the best way to deal with this? I've been thinking about replacing the mechanical switch with an SSR-is that the best option?

The pump is rated at 2 HP / 230 V / 10.7 Amps.The pressure switch is a Square D 9013FSG which is rated for 2HP at 230V.
** Correction: The pump is wired for 120V and is drawing 20 A when on

Attached are photos of the pump and switch.

[Messtechniker]

What you need is a snubber. Suitable rated RC in series across the arcing contacts.

[Gyro]

I agree on the snubbers as a long term life enhancement, but sadly those contacts are at (beyond) end of life - there's no way that you will get them back to nice flat contact faces, they are too splattered and they will continue to stick until replaced.

Hopefully you can purchase replacements separately.

[radioFlash]

Thanks for the suggestions. I've already replaced the switch and was looking for an improved long term solution-the snubber idea looks like it should do it.

How do you determine an appropriate R and C value? Would a Quencharc device from Cornell Dbuilier rated for 250VAC / .1 uF / 150 Ohm be reasonable?
This is the datasheet:
https://www.cde.com/resources/catalogs/Q-QRL.pdf

[NiHaoMike]

Could you get a switch rated for a lot more than 2HP, or failing that, use the switch to operate a contactor? The snubber will help (a lot) on opening but make matters a little worse on closing. An exception to that would be a "diode clamp" with a bridge rectifier across the contacts going to a capacitor, then some kind of load to discharge the capacitor. That load could be switched on only when the contactor is closed, in order to eliminate standby power usage.

[Gyro]

0.1uF/150R certainly looks in the right region for a contact snubber. The proof will be in the implementation though - if you can observe and compare the contacts switching with and without the snubbers fitted, the difference will be very obvious if they are working.

Fit one directly across each contact pair rather than a single one across the motor.

[MarkF]

You have bigger problems then burnt contacts on the pressure switch.
Find out what the real problem is.
My pressure switch has been working flawlessly for 25 years.

Is the pump starting/stopping too often?

Is the air pressure in the tank correct?
  Most have an air bladder.  Maybe it broke and the air pressure is incorrect.

Maybe there is a problem with the foot-valve and the pump bounces ON/OFF when it should just stop.

Have you noticed the pump running more often than it should?

Is the pump motor pulling more current than it should?


Edit:  You may also have a loose wire connection some where causing low voltage and higher current than normal and over heating.  Check all the connections from the main breaker box to the pump.

[TheMG]

The arcing damage on those contacts is much more than normal wear and tear, especially after only one year!

Have you measured the current that the motor is drawing to make sure it's within the motor's rating?

Also, how often is it cycling? When no water is being used, the pump should never run at all. If it does, you either have a leak somewhere or a bad check valve. When you run a faucet the pump should cycle no more than twice per minute, if it cycles more than that, you either have a defective pressure tank, not enough or too much charge in the bladder, or an inadequately sized tank.

[james_s]

I agree that something is not right. The well at our cabin was installed in 1973 and the original pressure switch is still working. Granted it doesn't get much use since it's turned off when nobody is there.

[radioFlash]

Those are good points.
* I just checked, and I was mistaken, the pump is running at 120 V not 230 V and is drawing 20A which is what the pump is rated for at 120 V. However, I think this puts it over the rating for the pump switch which is rated at 1.5 HP on 120V. I will see if I can find a switch rated for 2 HP at 120V.
* Based on your suggestion, I checked the the cut on/off points and adjusted them to reduce cycling. I think it is cycling normally. The pressure tank and pump were replaced three years ago. I will need to investigate if there is a leak. Thanks.

The arcing damage on those contacts is much more than normal wear and tear, especially after only one year!

Have you measured the current that the motor is drawing to make sure it's within the motor's rating?

Also, how often is it cycling? When no water is being used, the pump should never run at all. If it does, you either have a leak somewhere or a bad check valve. When you run a faucet the pump should cycle no more than twice per minute, if it cycles more than that, you either have a defective pressure tank, not enough or too much charge in the bladder, or an inadequately sized tank.

[MarkF]

The pressure switch rating is:
  Horsepower Rating (1-Phase) 1.5HP@115VAC - 2HP@230VAC

You have a 2HP motor.
However from your picture, it looks like it could be wired for 240VAC.
That would meet the spec for the switch.

It would require a new 2-pole breaker in the main breaker box and switching the connections at the pump.

[floobydust]

Those contacts look really chewed up, I wonder if there is another problem.
Like mushy power or a weak start capacitor. 2HP on 115VAC is at the limit, better to use 230VAC at that power level for lower current.

A snubber or MOV will work to prevent contact arcing but will not help if motor current is high.
You can get packaged surge protectors from your electrical supplier. Square D, Intermatic and many other companies make them but some are stupid overpriced.

[james_s]

I would definitely change to 240V if available, that will significantly reduce losses in the wiring and the motor will run a bit cooler without the supply voltage sagging.

I would also consider using a contactor to switch the power to the motor and have the pressure switch controlling power to the contactor coil. You can sometimes find nice industrial contactors for not much money on ebay.

[MarkF]

Interesting:

   Factory wired for 230VAC  (Some one changed it when installed)

[andy3055]

I tend to agree with most of the info above. Here is a link for a good site: https://www.hunker.com/12002953/how-to-troubleshoot-a-square-d-pumptrol

1. Make sure your switch is properly sized for the pump motor. Go for the higher rating if possible.

2. Make sure the cut-in and cut-out pressures are as specified and adjusted properly as in the literature of the switch and there is no "bouncing" of the contacts when cutting in/out. The contacts being so badly pitted confirms that you do not have a fast make/break at this switch.

3. Suggestion to use a contactor is very good. The idea is to make/break the contact as fast as possible to minimize the arcing. A contactor will do this better than a pressure switch directly in the circuit. Suggestion for a snubber is also a great idea.

In the end, you will have to experiment and observe which option gives the best arc suppression.

[TheMG]

I would definitely re-wire for 240V if possible. Half the current and won't be exceeding the rating of the switch anymore. I think a pressure switch with a higher rating is going to be difficult to find, as contactors are normally used for switching large loads.

[james_s]

It was probably replacing an older, smaller pump that was already 120V so they just wired the new one for 120V and left the circuit alone. I haven't seen your installation and am not familiar with your local electrical codes so either do your homework or hire a licensed electrician but you *should* be able to simply replace the breaker with a double pole type and use 240V on the existing wiring. One very important detail though is that the circuit MUST be dedicated, you have to be absolutely certain there are not other 120V loads on it. 120V is adequate for around 1HP to 1.5HP in a pinch but 2HP really is getting into 240V territory.

[radioFlash]

Rewiring it for 240 is possible, but the current wiring for the shed looks like it needs to be redone-it is a horror right now.  There's a 3 conductor cable to the shed (2 live and a neutral) bringing in 240. The well pump uses 240, but the pressure pump, light, and outlet are tied to one of the live wires and to neutral for 120. There's a cutoff switch/fuse box for the well pump (left) and another for the pressure pump(right).

I think I should put in a proper sub panel.

[floobydust]

I don't see the ground wires connected in the fuse panel, or anywhere really, which kind of makes me run away. It doesn't look safe.

A sub-panel is cheap, aside from the cost of new breakers. If you know the wire gauge and breaker on the main panel, you can see if this is worth it.

[james_s]

Judging by the plug fuses and cloth covered cable I'd guess the place is old enough that there may not have ever been a ground. In that case I would probably bond it all to the well casing unless there's a good reason that isn't done.

[andy3055]

Looking at those pictures makes me think you should not be mucking around in that shed until you rewire the whole place! This whole thing is growing day by day as you post new info. Apart from solving the contact problem, you need to think of a permanent solution for the complete installation at some stage. As a short term thing, you could convert the pump to run on 240 volts as suggested before and take other steps as listed by everyone to make things work. But eventually when you do up the place, you may end up having to change things around again. So, just do what needs to be done to get by for now and make sure any parts/equipment you buy can still be used later-unless they are not too expensive. Plan carefully so that you will not spend unnecessarily later.

[TheMG]

Yikes!

Looks like the wire nuts in that junction box have gotten hot. What's with that other junction box with the crimp butt splices? No apparent grounding either.

Honestly, if it were me, I'd rip everything out and re-wire from scratch, to modern codes.

[james_s]

Those are the old 3M wire nuts, they haven't gotten hot, they're covered in a flexible rubber material instead of hard plastic. They work fine although I don't recommend reusing them as once the wire insert and covering has deformed they don't tend to grip the wires well if you try to reinstall.

[jmelson]

Those are good points.
* I just checked, and I was mistaken, the pump is running at 120 V not 230 V and is drawing 20A which is what the pump is rated for at 120 V. However, I think this puts it over the rating for the pump switch which is rated at 1.5 HP on 120V. I will see if I can find a switch rated for 2 HP at 120V.

Can you get 240 V out to the well?  I think that it will be easier on the motor and your whole house electrical system to have it run off 240 V.
(Unless you like having all the lights in the house dim every time the pump starts.)  With the motor set for 240 V, you could use a 240 V 50 A
SSR to control it.  You need to oversize the SSR to accommodate the starting surge.

Jon

[james_s]

I wouldn't use a SSR for this application, they have significantly higher losses than a mechanical contactor and when they fail they usually fail shorted on. SSRs are good for applications that switch frequently like PID based heating controllers, a well pump should not be switching all that frequently.