Am I looking at the correct chart when sizing wire for a well pump? I'm looking at 430.248 and using the 230 volt column. The well in question is 5 horsepower. Would I be correct in using a 10-2 NM-B as the chart claims that the full load current is 28 amps? The well contractor is saying that it needs to be a minimum 8-2 NM-B. I'm not sure where he is getting his calculation from. This is at a residential home with a 200 amp single phase panel.
well horsepower ratings
- Thread starter crtemp
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Keep in mind your minimum conductor ampacity would need to be 125% of that 28 amps, which is 35 amps.
NM cable must be used at 60 C ampacity but can use 90C ampacity as the starting point for ampacity adjustments (if it is NM-B)
If you have a conductor that can be used at 75C ampacity then 10 AWG would be acceptable.
Also keep in mind well guys often use a chart that factors in voltage drop.
NM cable must be used at 60 C ampacity but can use 90C ampacity as the starting point for ampacity adjustments (if it is NM-B)
If you have a conductor that can be used at 75C ampacity then 10 AWG would be acceptable.
Also keep in mind well guys often use a chart that factors in voltage drop.
JFletcher
Senior Member
- Location
- Williamsburg, VA
I'd run #8, or possibly #6 if the well is far away (total distance to pump, not just straight line to the well cap). If in doubt, exceed code.
UF is limited to 60*C iirc.
UF is limited to 60*C iirc.
- Occupation
- Licensed Electrician
What are you gaining by exceeding code? Your already oversized to max amps possible per HP by the charts in 430 instead of the actual FLA, then your conductors are upsized another 125% on top of that, plus the voltage drop tolerance already engineered into motors.
Dzboyce
Senior Member
- Location
- Royal City, WA
- Occupation
- Washington 03 Electrician & plumber
Pump installers size wire from the Franklin AIM manual. It's wire sizing charts allow for voltage drop. Remember your wire length can be 100's of feet long to the motor. The NEC charts don't allow for voltage drop. That is a separate calculation.
http://www.franklinwater.com/media/110562/M1311_60_Hz_AIM_12-14-WEB.pdf
Page 11 has the wire charts for single phase motors. Maximum lengths listed are for service entrance to motor total allowable length.
for example using your 5 hp 230 volt single phase motor as an example,using the 60 degree chart. The smallest wire that can be used is #10 for a maximum length of 180 feet. However the 180 feet is in bold print. That means this size wire must be individual conductors, in fee sir or water, not in magnetic enclosures, conduit, or direct buried. #8 wire can be used for a maximum of 280 feet. #6 has a maximum length of 450 feet, service entrance to motor.
The wire charts must be followed for warranty on the pump motor.
http://www.franklinwater.com/media/110562/M1311_60_Hz_AIM_12-14-WEB.pdf
Page 11 has the wire charts for single phase motors. Maximum lengths listed are for service entrance to motor total allowable length.
for example using your 5 hp 230 volt single phase motor as an example,using the 60 degree chart. The smallest wire that can be used is #10 for a maximum length of 180 feet. However the 180 feet is in bold print. That means this size wire must be individual conductors, in fee sir or water, not in magnetic enclosures, conduit, or direct buried. #8 wire can be used for a maximum of 280 feet. #6 has a maximum length of 450 feet, service entrance to motor.
The wire charts must be followed for warranty on the pump motor.
JFletcher
Senior Member
- Location
- Williamsburg, VA
When I first started, I nor the gentleman I worked for was licensed. Exceeding code, which is the minimum install allowed, is never a bad idea. I still subscribe to the idea of "if in doubt, exceed code".
We do not know how far the OP's install is.
This well in question is 1000 feet deep. The only wire I am contracted to install is from the panel to the exterior of the home which is only about a 30' run. It's another 60' from the house to the well head. Would I have to up size the wire that I pull to allow for voltage drop or just does only the wire that is 1000' need to up'd?
Dzboyce
Senior Member
- Location
- Royal City, WA
- Occupation
- Washington 03 Electrician & plumber
I just noticed that you are in Washington state. That means that the pump installer is also a licensed electrician. You need to install what he says he needs.
This is is why I usually install my wiring for the pump all the way to the breaker panel, and install the proper breaker myself.
If he's using a single phase motor, the circuit will need a 60 amp breaker. There's a very high probability that the pump installer will be installing a 3 phase motor with a vfd, converting the incoming single phase to 3 phase. Depending on the brand, you might need to install a 40 amp or a 50 amp breaker.
This is is why I usually install my wiring for the pump all the way to the breaker panel, and install the proper breaker myself.
If he's using a single phase motor, the circuit will need a 60 amp breaker. There's a very high probability that the pump installer will be installing a 3 phase motor with a vfd, converting the incoming single phase to 3 phase. Depending on the brand, you might need to install a 40 amp or a 50 amp breaker.
He said he wanted a 40 amp breaker and 4 gauge wire ran from the house to the well head, but again I'm not contracted to do that part. For this particular builder I only install the indoor wiring and it is up to the home owner to do anything outside of the house (service wire, well wiring, septic system, etc)
Dzboyce
Senior Member
- Location
- Royal City, WA
- Occupation
- Washington 03 Electrician & plumber
Has the pump installer said where he's going to install the pump control box? He's also got a pressure tank and other gear to install. That equipment needs to be protected from freezing.
He should be pulling his own electrical permit for his work also. He might only have an 03A license and be restricted to a branch circuit supplied by others. Still needs his separate permit though.
He should be pulling his own electrical permit for his work also. He might only have an 03A license and be restricted to a branch circuit supplied by others. Still needs his separate permit though.
I don't think he can wire it himself because he was trying to get me to do it but the job is a couple hours away and I don't have time to do it anyway. He will have to hire someone else.
As for the pressure tank and control box I believe they are building a small well house at the well head.
Dzboyce
Senior Member
- Location
- Royal City, WA
- Occupation
- Washington 03 Electrician & plumber
If there's a pump house your branch circuit needs to go to a sub panel in the pump house. Now you've got a 4 wire circuit your two conductors, a neutral and a ground wire. The pump house has to have an exterior light over the man door, an interior light, a 110 volt outlet, a heat source, plus the pump circuit. And the pump house will require two ground rods. All inspected by L&I.
For that pump house with a 5 hp pump, I'd be running #4 thhn from the main panel to the sub panel in the pump house.
For that pump house with a 5 hp pump, I'd be running #4 thhn from the main panel to the sub panel in the pump house.
Ya I know but again, all I'm contracted to do is run the power for the well and stub it outside. If they need anything beyond that is the owners issue. I was mostly just curious to make sure I am running the correct size wire which I didn't. I didn't see the 125% rule for motors so it would have needed a 8 gauge wire. But even that is not my fault as I am only contracted to run a 30 amp circuit which I did. I came to find out the well depth a month after the house was wired.
JFletcher
Senior Member
- Location
- Williamsburg, VA
1 conductors per phase utilizing a #2 Copper conductor will limit the voltage drop to 4.26% or less when supplying 28.0 amps for 1000 feet on a 240 volt system.
For Engineering Information Only:
95.0 Amps Rated ampacity of selected conductor
0.1808 Ohms Resistance (Ohms per 1000 feet)
0.045 Ohms Reactance (Ohms per 1000 feet)
12.0 volts maximum allowable voltage drop at 5%
10.211. Actual voltage drop loss at 4.26% for the circuit
0.9 Power Factor
from Southwire dot com voltage drop calculator.
For Engineering Information Only:
95.0 Amps Rated ampacity of selected conductor
0.1808 Ohms Resistance (Ohms per 1000 feet)
0.045 Ohms Reactance (Ohms per 1000 feet)
12.0 volts maximum allowable voltage drop at 5%
10.211. Actual voltage drop loss at 4.26% for the circuit
0.9 Power Factor
from Southwire dot com voltage drop calculator.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The real answer is what voltage drop is tolerable and where?
I myself have little issue with minimal size for the first 30 feet then upsizing for VD for the next 1000 feet. The drop on the first 30 feet won't be that significant. Now that it has been mentioned there is a well house though - I would expect other loads besides just the well pump to be a factor as well.
Barbqranch
Senior Member
- Location
- Arcata, CA
- Occupation
- Plant maintenance electrician Semi-retired
Just because the well is 1000 feet deep doesn't mean the pump is down at the bottom. My 200 foot well (expensive dry hole in the ground at 180 feet) has a static water level around 10 feet below grade, and my pump will only pump it down to around 100 feet in the summer. The well driller should know the local water conditions.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Your pump is down around that 100' mark then, they gave you another 100' for when the water table drops or in drought conditions to lower the pump.
Even a perfect positive displacement pump can only pull ~25' under STP (standard temperature and pressure).
1000' well wouldnt be drilled if they had water at 500', right?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
But a jet pump mounted at the surface can still pump water from a multi-hundred foot well once it has been primed.
I'm just curious who contracted you originally to install the 30 amp circuit for the well?
Is this something you spelled out originally or did someone specifically ask for a 30 amp circuit?
Either way, if you've got that in writing one way or the other it would be an adder to upgrade it to what the well people require and it shouldn't be an issue.
I don't know why you'd want to step out on your own and undersize the feeder that they are asking for.
Seems you would be assuming the responsibility of the well equipment once you did that and with a 1000' well your pockets had better be "pretty deep" to take that responsibility on.
JAP>
Barbqranch
Senior Member
- Location
- Arcata, CA
- Occupation
- Plant maintenance electrician Semi-retired
The water in the 1000 foot layer may be under quite a bit of pressure, such that the static water level is quite a bit higher. Think of an artesion well, which has water pouring out of the well casing after it is drilled.
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