Do I need to pull the pump?

[Toby Hanson]

Hello everyone,

I have a Flotec 3/4 HP three-wire pump and control box. It's 90' down in a 100' six-inch well. It quit pumping water on Monday. I checked the fuses in the service disconnect and one of them was blown. I replaced the fuse and it pumped for a couple more hours and then the fuse blew along with the starting capacitor. I replaced the fuse and capacitor again and the capacitor blew again yesterday. I got another control box today and installed it and measured the amperage on each of the wires going to the pump before the capacitor blew. After it blew I checked the resistance on each of the wires going down to the pump. Here's the data:

Resistance
Red-Yellow: 12.2 ohms; range should be 11.1-13.6
Red-Black: 15.2 ohms; range should be 2.7-3.3
Yellow-Black: 4 ohms; 13.8-16.9

Resistance to Ground
Red-Ground: 0 ohms
Yellow-Ground: 0 ohms
Black-Ground: 0 ohms

Amperage
Red: 4.3A
Black: 8.1A
Yellow: 0.2A
Green: 11.8A

I expected the current on the red wire to drop once the relay opened to take the capacitor out of the circuit but it never did. Based on the readings, I think the pump needs to be pulled out and replaced but I want to make sure before I dedicate a day to pulling and replacing the pump.

 

[Reach4]

Resistance
Red-Yellow: 12.2 ohms; range should be 11.1-13.6
Red-Black: 15.2 ohms; range should be 2.7-3.3
Yellow-Black: 4 ohms; 13.8-16.9

Check the documentation for your "range should be" resistances that you wrote down again. Your as-measured resistances look about right, allowing for some wire resistances.

 

[Sponsor]

 

[Toby Hanson]

Check the documentation for your "range should be" resistances that you wrote down again. Your as-measured resistances look about right, allowing for some wire resistances.

The only documentation I have for this system is the values printed on the inside of the control box. The Red-Black resistance is higher than the specified range and the Yellow-Black resistance is lower than the specified range. I'm also concerned about the lack of resistance to ground. That makes me think the motor is shorted to ground. I'm no expert on electric motors but I think the reading to ground should be out-of-limit.

 

[Texas Wellman]

Yep. Shorted to ground. Pull'er out. And please don't use a crap pump like flotech.

 

[Reach4]

The only documentation I have for this system is the values printed on the inside of the control box.

Do both the new and old box show the same values printed inside? How about a photo of the resistance table for one of the boxes.

The Red-Black resistance is higher than the specified range and the Yellow-Black resistance is lower than the specified range. I'm also concerned about the lack of resistance to ground. That makes me think the motor is shorted to ground. I'm no expert on electric motors but I think the reading to ground should be out-of-limit.

Good point on the resistance to ground. That does not make sense. I was thinking that the meter maybe was showing infinite resistance (out-of-limit) and you had just written 0. If red, blue, and yellow were all 0 ohms to ground, you would expect each of them to be 0 with respect to each other.

Do you have another meter for the yellow-to-ground resistance measurement?

 

[Toby Hanson]

Yep. Shorted to ground. Pull'er out. And please don't use a crap pump like flotech.

What pump do you recommend?

 

[Toby Hanson]

Do both the new and old box show the same values printed inside? How about a photo of the resistance table for one of the boxes.

Here's a pic of the resistance table for the new box. The numbers are within a tenth of an ohm of the values for the old box.

https://i.imgur.com/8YzpXM1.jpg

 

[Reach4]

Here's a pic of the resistance table for the new box. The numbers are within a tenth of an ohm of the values for the old box.

Resistance
Red-Yellow: 12.2 ohms; range should be 11.1-13.6 11.8-13.0
Red-Black: 15.2 ohms; range should be 2.7-3.3 14.4-16.6
Yellow-Black: 4 ohms; 13.8-16.9 2.6-3.6

 

[Craigpump]

Grundfos, put new pump cable in while you're at it. Be sure to use a stainless steel male X insert at the pump if you're using poly pipe.

 

[Valveman]

When you have 100% short to ground, there is no reason to check any further.

 

[Reach4]

When you have 100% short to ground, there is no reason to check any further.

With 100% short on all 3 wires to ground, there is no way to get those wire-to-wire resistance numbers that he measured. Something is off on his resistance to ground test. Now maybe there is a 1000 ohm short to ground (which calls for pulling the pump) and he has the meter in the 20 megohm range so it reads zero. But I cannot see him reading zero if he adjusts his meter. If that was what is going on, fine. But I think it is worth re-checking that aspect.

 

[Toby Hanson]

With 100% short on all 3 wires to ground, there is no way to get those wire-to-wire resistance numbers that he measured. Something is off on his resistance to ground test. Now maybe there is a 1000 ohm short to ground (which calls for pulling the pump) and he has the meter in the 20 megohm range so it reads zero. But I cannot see him reading zero if he adjusts his meter. If that was what is going on, fine. But I think it is worth re-checking that aspect.

I rechecked the resistance measurements this morning with a different meter. They were the same. Both meters were auto-ranging and read in ohms, not mega or kilo. The numbers didn't make sense to me, either, but I ended up replacing the pump anyway. Just for the sake of comparison, after installing the new pump I read the resistance on each of the pairs of wires and then the resistance to ground from each of them. The resistance for all the pairs of wires was within spec and the resistance to ground from each of them was infinite, which is exactly what I would expect with a brand new pump.

I couldn't get a Grundfos on short notice so I bought the best pump I could find, a Sta-Rite. I hope it does well.

Thanks for all of your responses!

 

[Amy Lee Goodwin]

Hello everyone,

I have a Flotec 3/4 HP three-wire pump and control box. It's 90' down in a 100' six-inch well. It quit pumping water on Monday. I checked the fuses in the service disconnect and one of them was blown. I replaced the fuse and it pumped for a couple more hours and then the fuse blew along with the starting capacitor. I replaced the fuse and capacitor again and the capacitor blew again yesterday. I got another control box today and installed it and measured the amperage on each of the wires going to the pump before the capacitor blew. After it blew I checked the resistance on each of the wires going down to the pump. Here's the data:

Resistance
Red-Yellow: 12.2 ohms; range should be 11.1-13.6
Red-Black: 15.2 ohms; range should be 2.7-3.3
Yellow-Black: 4 ohms; 13.8-16.9

Resistance to Ground
Red-Ground: 0 ohms
Yellow-Ground: 0 ohms
Black-Ground: 0 ohms

Amperage
Red: 4.3A
Black: 8.1A
Yellow: 0.2A
Green: 11.8A

I expected the current on the red wire to drop once the relay opened to take the capacitor out of the circuit but it never did. Based on the readings, I think the pump needs to be pulled out and replaced but I want to make sure before I dedicate a day to pulling and replacing the pump.