Help sizing well circuit
- Thread starter crtemp
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With well pumps, voltage drop is normally a significant factor and your post does not mention distance.
Most well pump manufacturers have data available showing recommended wire sizes based on distance.
Here is one example:
http://www.aquascience.net/submersible-pumps/index.cfm?wiresize=1
Most well pump manufacturers have data available showing recommended wire sizes based on distance.
Here is one example:
http://www.aquascience.net/submersible-pumps/index.cfm?wiresize=1
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I edited my post as once I found a link to one well pump manufacturer I discovered #14 was acceptable for distances further than I though or had experienced.
See that link.
(I have never seen a well wired with 14...but obviously......
)
See that link.
(I have never seen a well wired with 14...but obviously......
)I have never wired one in 14 either. I usually just use #10 thhn. I'm just a residential guy and hardly ever wire wells. Usually the well pump companies take care of it. I am not really familiar with article 430 since it never really pertains to anything I wire, so I decided to read through it and the table I mentioned in my original post didn't seem right so I just wanted to make sure I was reading it correctly. Am I reading the chart you linked correctly in that 14 gauge is good for up to 353 feet? Wow
Does this count on the wire length from the panel to the well head or from the panel to the well head and then down to the pump? If I remember correctly I think there is usually #10 going down to the pump almost always
- Occupation
- Licensed Electrician
Given everything you have described 12 AWG would be just fine. You may be able to use 14 but I wouldn't not for any legal reason, just because
As far as the wire going down to the pump- It may be anything. Well guys tend to be an outlaw bunch when it comes to wiring.
ptonsparky
Tom
- Occupation
- EC - retired
Sizing of the wire can be useful in limiting the startup torque exerted on a drop pipe with a submersible. Voltage drop is not always a bad thing.
kwired
Electron manager
- Location
- NE Nebraska
I come up with 3.25 volts dropped over 75 feet of 14 AWG with a load of 6.9 amps.
You have to remember you will only draw 6.9 amps if the motor is fully loaded and is being supplied with 230 volts after any voltage drop is factored in.
Load on the motor is going to depend on how many GPM it is moving and how much vertical lift is necessary.
Raise the input voltage or change the actual load on the motor and things all change.
3.25 volts drop on 230 is only 1.4% drop. You do need to consider how much conductor and what size there is from the top of well to the pump also. and there is a good chance your actual input voltage is higher than 230, though we often don't consider this, the reality is many times the applied voltage is closer to 240 and the motor rated voltage is 230.
If this is a three wire instead of a two wire pump motor then current is split and voltage drop is not the same either. You will have full current on the common wire but it will split (not necessarily equally) across the two windings and the other two conductors.
You have to remember you will only draw 6.9 amps if the motor is fully loaded and is being supplied with 230 volts after any voltage drop is factored in.
Load on the motor is going to depend on how many GPM it is moving and how much vertical lift is necessary.
Raise the input voltage or change the actual load on the motor and things all change.
3.25 volts drop on 230 is only 1.4% drop. You do need to consider how much conductor and what size there is from the top of well to the pump also. and there is a good chance your actual input voltage is higher than 230, though we often don't consider this, the reality is many times the applied voltage is closer to 240 and the motor rated voltage is 230.
If this is a three wire instead of a two wire pump motor then current is split and voltage drop is not the same either. You will have full current on the common wire but it will split (not necessarily equally) across the two windings and the other two conductors.
ptonsparky
Tom
- Occupation
- EC - retired
I say yes. We use A/C disconnects for most residential type wells.
kwired
Electron manager
- Location
- NE Nebraska
430.102(A) requires a disconnect within sight of the motor controller. If this control box makes/breaks motor current for the purpose of starting/stopping the motor then it is a motor controller.
shortcircuit2
Senior Member
- Location
- South of Bawstin
75 feet from the service panel to the pump motor? Or 75 feet to the control box and storage tank? Around here pumps are 100-600ft deep in the ground...75ft away from the building. I run minimum #12 to the not so deep wells and #10 to the deep wells.
If yours has a metal well casing, make sure to bond/ground it to the EGC of the branch circuit...250.112(M)...probably the only (M) in the NEC...this is so important any many electricians don't ground the casing.
ptonsparky
Tom
- Occupation
- EC - retired
Right. The old standard two pole pressure switch is/was often the controller, not the box with capacitors, potenial relay and thermal overloads.
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