Solution for existing pump electrical problem.

[kinnison]

My house was built 35 years ago with a 1hp Franklin Electric submersible. It has operated flawlessly but no pump lasts forever and I desire more GPM for irrigation. Here's the rub: This pump is on a 240 volt 20 amp breaker. According to what I read, the pump cicuit should have 30 amp to allow for startup current. I am not sure how it slipped past an inspector. The pump has not tripped the breakers in the 22 years we have lived here. I would choose to go to a higher horsepower pump but I should not be running even the pump that I have. The AC to the pump is buried and 150' long. A major pain to dig it all up to run heavier gauge wire.
So, the only solution I see is to put a 3/4hp pump down in the well. This well is near 500' deep although I don't think the current pump is that far down. A 3/4hp pump will produce a very meager flow from those depths. Can I use booster pump in line between the submersible and the existing pair of pressure tanks? IOW will a booster pump's suction aid the submersible pump in getting the needed GPM?

 

[Valveman]

My book shows a 1HP only needs a 25 amp breaker. 20 amps is close enough if you use a 3 wire motor with a control box. Might trip on a 2 wire motor. If you need more water and pressure you don't want to go with a lower horsepower. A 5GPM, 3/4HP won't even pump from 500'. Most likely the well is 500' deep, the pump is set at maybe 300', and the actual water level is probably only 50' deep or so. That means a 10 GPM, 1HP might be the best fit. But it would be best to know how deep and what GPM series the old pump is before selecting a new pump.

One thing with going to a larger pump is that cycling becomes more of a problem, but simply adding a Cycle Stop Valve can solve all of that.

 

[Sponsor]

 

[bigb56]

Motor rules, including well pumps, don't follow the small conductor rules in the NEC, they are excepted. Normally the pump manufacturer will stipulate the minimum circuit ampacity and the maximum fuse or circuit breaker allowed. This could result in #12 or even #14 wire being used on a 25 or 30 amp breaker and still be perfectly safe and legal. The breaker protects against short circuit and the motor has overload protection built in. The larger breaker is needed for startup current and in some (most) cases can be up to 250% of the load running current.

The other consideration regarding wire size though is voltage drop on long runs. At 150 feet you should do a voltage drop calculation on the pump you are considering to verify that the present wiring is enough to limit the VD to an acceptable level.

Here's some additional info: https://viox.com/what-size-breaker-for-well-pump/

 

[bigb56]

Here is a wire size chart by Franklin AIM. What size is the 150 foot run, and what size are the wires going down the 500 feet to the pump? This will get us in the ballpark of how big you can go.

Keep in mind you can upsize the 500 foot section with the new pump and even if it doesn't match the 150 foot section it will still reduce the voltage drop in the entire circuit.

Let's get that figured out first and go from there. Also, if you have any larger pumps in mind post them here.

 

[kinnison]

It is incredible to receive such a large quanity of excellent information so quickly! I thank each of the responders for the taking time to respond. I understand now what further data is needed. My first thought is that I will work out the math on VD (assuming upsizing on the well wiring) and see if I can sqeak a 1.5 hp 3wire pump down there. Given the (almost enough) I'm getting on an elderly 1hp pump, I think a new 1.5hp might do the trick. Some data I won't know until I pull the old pump and see how far down it was. As an aside, we have never run the well dry even though it doesn't rain here from mid-May till mid-September. Thanks again and to the Forum.