No ground wire

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I can understand the physics of current carrying conductors being run in close proximity to mitigate electric fields. But don't see why a normally non current carrying conductor, who's only purpose is to open the OCPD in the event of a fault would have to be in close proximity.
 
Sea Nile said:
I can understand the physics of current carrying conductors being run in close proximity to mitigate electric fields. But don't see why a normally non current carrying conductor, who's only purpose is to open the OCPD in the event of a fault would have to be in close proximity.
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Because where AC current flows in conductors that are physically separated from each other the impedance goes up as a result of inductive reactance. This increased impedance restricts the flow of fault current and can result in a much longer clearing time for the OCPD. Often placing the trip time into the short time or even long time part of the trip curve instead of being in the instantaneous part of the curve where it should be.
As I recall, there is a table in the IEEE Green Book, that shows a 12" separation doubles the impedance of the fault return path.
 
LarryFine said:
Because the well casing qualifies as an electrode.
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Given the 600' from the power source, I don't see the well casing as being a required grounding electrode.
250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system ...
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don_resqcapt19 said:
where AC current flows in conductors that are physically separated from each other the impedance goes up as a result of inductive reactance. This increased impedance restricts the flow of fault current and can result in a much longer clearing time for the OCPD.
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Good stuff, would a solution be to put a fused disconnect at the pump house with a smaller fuse than you would normally use?
 
Based on my experience with customers and well pumps, my 1st question would be "do you have 3 phase power at the source ?" :)
There is an amazing amount of misunderstanding on phases and voltage by folks not in our field.
If 3 phase is available, then don's Post 28 sums it up.
 
augie47 said:
Based on my experience with customers and well pumps, my 1st question would be "do you have 3 phase power at the source ?" :)
There is an amazing amount of misunderstanding on phases and voltage by folks not in our field.
If 3 phase is available, then don's Post 28 sums it up.
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There is quite a few three phase well pumps anymore run by a VFD with single phase input
 
I seem to remember Mike having a graphic that showed a EGC strapped to the outside of a conduit. Really seems the same as retrofit of a EGC to an older two wire system to allow 3 prong devices.
 
jimport said:
I seem to remember Mike having a graphic that showed a EGC strapped to the outside of a conduit. Really seems the same as retrofit of a EGC to an older two wire system to allow 3 prong devices.
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I believe there is length limitations where the EGC is permitted to be outside the raceway and mostly is for flexible conduits. Not sure why it was ever permitted other than maybe for use with segments of flexible metal conduits where a bonding jumper is required around the flex but no EGC was pulled inside raceway.

The impedance issues still exist with running a separate EGC to old two wire wiring methods. Circuit length is often short enough it isn't too big of an issue. You still can't run a new install of two wire and route an EGC separately, it is just one option for dealing with something existing.
 
Dennis Alwon said:
Why does the customer want a 3 phase pump?
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Yeah, I wonder if this is a case of a customer wanting something fancy and expensive for some perceived but invalid reason. I am generally not a fan of constant pressure/ variable speed water systems. It's more expensive and more stuff to fail. Many pressure tanks are undersized and this can lead to cycling or noticeably variable water pressure. Usually just providing a proper or even oversized pressure tank is all one needs.
 
jimport said:
I seem to remember Mike having a graphic that showed a EGC strapped to the outside of a conduit. Really seems the same as retrofit of a EGC to an older two wire system to allow 3 prong devices.
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1662312493478.png

303.(B)(2) Grounding and Bonding Conductors.

Equipment grounding conductors shall be permitted to be installed outside a raceway or cable assembly where in accordance with the provisions of 250.130(C) for certain existing installations or in accordance with 250.134, Exception No. 2, for dc circuits. Equipment bonding conductors shall be permitted to be installed on the outside of raceways in accordance with 250.102(E).
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This is for bonding jumpers

1662312534030.png
 
It bears repeating that the 300.3(B) graphic only applies to ferrous raceways, as 300.3(B)(3) would allow the EGC outside the raceway or cable for nonferrous wiring methods. The graphic could use updating to reflect that.

Cheers, Wayne
 
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