[mr.T]

I don't know what type of well pump I have as thr previous homeowner didn't give any
records. But it's on a 30A double pole breaker and I see that it's run with 12G wire. Should this actually be a 20A breaker? I found online that most pumps 3/4 HP and below would need a 20A breaker.

 

[dcwired]

There is no way to know without knowing for sure what the pump size is, however 20 amp is typical for #12 wire. Try a 20 amp breaker to see if it holds. 20 amp @ 240 volts is a lot.

 

[rjniles]

Hard wired motors have different rules for breaker and conductor sizing. Without seeing the motor nameplate or model number there is not way to be sure.
The overload protection shall be sized according to the motor nameplate current rating [430.6(A), 430.32(A)(1), and 430.55].

 

[MTVhike]

My well is on a 30A, double pole breaker. 10Ga wire.

 

[viper]

We make estimations in the field by doing a current test on the wires. It is not fool proof but pulling the pump is not always practical. If you have a 3 wire pump, you will have a "start box" with a capacitor in it, and those are usually sized for the pump, so that is another way to determine.

But in ANY case, it is a 100% no-no to have 12ga wire on a 30A breaker! I personally don't like to see pumps on any breaker that is larger than needed. That means if you have a 3/4 pump, it is likely I would install a 15A breaker with the 12ga wire. Why? Because I stand a better chance of saving the pump if something happens. Breakers don't trip for no reason.

A 1HP pump will still hover at around 10A current at 240V, so you would have to have a big gurl pump for a a 30A breaker. We have a 1.5HP HVLP pump running on a 20A circuit happily at this moment.

 

[seharper]

I don't know what type of well pump I have as thr previous homeowner didn't give any
records. But it's on a 30A double pole breaker and I see that it's run with 12G wire. Should this actually be a 20A breaker? I found online that most pumps 3/4 HP and below would need a 20A breaker.

It depends. A breaker is looking for 3 kinds of fault.

• overload
• a hot-neutral short
• a "bolted" hot-ground fault (i.e. short to ground)

If the circuit powers primarily a motor load (you would think so, golly!), and the pump motor has overload protection on the motor, then you can rely on the motor's overload protection and the breaker does not need to do that job. A somewhat larger breaker (within reason) will still detect shorts and bolted faults reasonably well.

In that case, the motor rules, NEC Article 430, allow you to enlarge the breaker somewhat to prevent "nuisance trips" from motor startup surge. You have to look at the motor nameplate or instructions, which would state the maximum breaker allowed. If that doesn't state, Article 430 has a formula.

 

[viper]

It depends. A breaker is looking for 3 kinds of fault.

• overload
• a hot-neutral short
• a "bolted" hot-ground fault (i.e. short to ground)

If the circuit powers primarily a motor load (you would think so, golly!), and the pump motor has overload protection on the motor, then you can rely on the motor's overload protection and the breaker does not need to do that job. A somewhat larger breaker (within reason) will still detect shorts and bolted faults reasonably well.

In that case, the motor rules, NEC Article 430, allow you to enlarge the breaker somewhat to prevent "nuisance trips" from motor startup surge. You have to look at the motor nameplate or instructions, which would state the maximum breaker allowed. If that doesn't state, Article 430 has a formula.

Harper, I said what I said, simply based on 25y experience worth with these. I think I've seen it all. People install larger breakers because they have a 500ft run to the pump PLUS the down hole cable, or their plumbing is plugged.

IDK, but is nearly all residentials we do, 20A covers them.

 

[anderep]

My 3hp well pump is in 30 amp breaker. Be carefull measuring current on motors, if capacitors are old your power factor can be crap leading you to the wrong conclusion. Running amp are 14-15, and starting amps 60-70 amps.

 

[mr.T]

We make estimations in the field by doing a current test on the wires. It is not fool proof but pulling the pump is not always practical. If you have a 3 wire pump, you will have a "start box" with a capacitor in it, and those are usually sized for the pump, so that is another way to determine.

But in ANY case, it is a 100% no-no to have 12ga wire on a 30A breaker! I personally don't like to see pumps on any breaker that is larger than needed. That means if you have a 3/4 pump, it is likely I would install a 15A breaker with the 12ga wire. Why? Because I stand a better chance of saving the pump if something happens. Breakers don't trip for no reason.

A 1HP pump will still hover at around 10A current at 240V, so you would have to have a big gurl pump for a a 30A breaker. We have a 1.5HP HVLP pump running on a 20A circuit happily at this moment.

On top of that, when I changed out the pressure switch a couple of years ago it was on 14ga wire. And a couple of other circuits had 20A breakers with 14ga wire, which leads me to not trust anything was done correctly. I think I will change it to 20A and see if it ever trips.

 

[tstex]

My well, which is much shallower, and it was mentioned previously, depends on the depth of your well, and thus how many feet you have to go down to prevent voltage drops. the conductors to most well houses serve both the well pump and pressure switch.

Wells are also something that you do not want to fail on marginal overloads. Therefore, sizing up is much better than sizing "what you might think is just the right capacity". I am pretty sure my well is a DP 30amp w 10 ga/ I will check and let you know the next time I am at my ranch,

 

[rjniles]

On top of that, when I changed out the pressure switch a couple of years ago it was on 14ga wire. And a couple of other circuits had 20A breakers with 14ga wire, which leads me to not trust anything was done correctly. I think I will change it to 20A and see if it ever trips.

Personally I would leave well enough alone. KISS, if it ain't broke........

 

[viper]

My well, which is much shallower, and it was mentioned previously, depends on the depth of your well, and thus how many feet you have to go down to prevent voltage drops. the conductors to most well houses serve both the well pump and pressure switch.

Wells are also something that you do not want to fail on marginal overloads. Therefore, sizing up is much better than sizing "what you might think is just the right capacity". I am pretty sure my well is a DP 30amp w 10 ga/ I will check and let you know the next time I am at my ranch,

You seem to be confusing a few things. It is 100% prudent and proper to install 10ga wire due to a long distance shot and voltage drop, but that is not going to change the amperage needs of the pump, so doing it the right way is many times 10ga wire with a 20A breaker. Actually, I prefer a motor start or fuses to further protect the pump.

A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more.

A pump should never "overload". There should never be an event that causes that. Giving them more amps does not make them feel better, it just ensures if one tries to sand lock, the whole thing is going to burn up, vs possibly tripping a breaker and saving it.

 

[viper]

Confirm if you have a 2 wire or 3 wire pump. Follow the wire from the breaker to the well head. On a 3 wire, there would exist a small meter box about 6x10" and 3" thick.

I always recommend to people to learn and know as much as possible about their well and gear. Why? Because when it breaks is not the time to learn things and that information accelerates a repair. Case and point, we had to do a repair for a property where we installed the previous pump 10y earlier. We had all the specs on the install, and showed up with the same pump just to ensure we could "make it rain" on one trip.

Many times there is something quite shady about an install that all has to be fixed during a repair.

 

[tstex]

You seem to be confusing a few things. It is 100% prudent and proper to install 10ga wire due to a long distance shot and voltage drop, but that is not going to change the amperage needs of the pump, so doing it the right way is many times 10ga wire with a 20A breaker. Actually, I prefer a motor start or fuses to further protect the pump.

A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more.

A pump should never "overload". There should never be an event that causes that. Giving them more amps does not make them feel better, it just ensures if one tries to sand lock, the whole thing is going to burn up, vs possibly tripping a breaker and saving it.

Viper said: "A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more."

vip, I think you might be confused, but not in a bad way...not sure where you are from or how your well is configured, but pls see the video below - this is how my well is configured....maybe you are referring to a pressure relief valve, not a pressures switch

 

[viper]

Viper said: "A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more."

vip, I think you might be confused, but not in a bad way...not sure where you are from or how your well is configured, but pls see the video below - this is how my well is configured....maybe you are referring to a pressure relief valve, not a pressures switch


A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more.

I didn't watch the video. I don't need to. That is a pressure switch, and it is ONLY a switch! Which means it consumes no power.. Sorry if my explanation was confusing. Yes, you certainly run wires to it, but it consumes zero power. It is 100% mechanical. There is a rubber diaphragm in the bottom with a spring and 1/4" pipe nipple that is notorious for plugging up and people throw them away when a a 5min cleanout will fix them.

 

[rjniles]

Viper said: "A pressure switch pulls no power...none! It is a mechanical device that operates based on water pressure, and nothing more."

vip, I think you might be confused, but not in a bad way...not sure where you are from or how your well is configured, but pls see the video below - this is how my well is configured....maybe you are referring to a pressure relief valve, not a pressures switch

Viper is 100% correct. The pressure switch uses no power. It is like the switch on the wall that controls your ceiling light, the switch merely closes the circuit to the light. The light uses power the switch does not. With a well pressure switch, the pressure in the storage tank opens and closes the pressure switch

 

[tstex]

point taken - but my focus of the conversation was where the wiring comes in and the voltage needs of the of the load to side pump and the line side from the CB...

 

[betelgeuse]

But in ANY case, it is a 100% no-no to have 12ga wire on a 30A breaker!

Not when dealing with motors. A single phase can have a breaker up to 250% of the motor current without increasing the wire size. A 3HP motor uses #12 wire and can have up to a 35A breaker (according to the SqD Motor Data Calculator)

 

[viper]

Not when dealing with motors. A single phase can have a breaker up to 250% of the motor current without increasing the wire size. A 3HP motor uses #12 wire and can have up to a 35A breaker (according to the SqD Motor Data Calculator)

Could you cite code on that? It was my understanding that IRC overrides std NEC.

 

[Frank Lavorngia]

My well is on a 30A, double pole breaker. 10Ga wire.

They likely used #10 because of the distance. I do on almost all wells. Then I install the #10 on a 20 amp breaker.