EGC pigtail in pump control box?
Next in the saga of wiring a pump control box:
The metal control box chassis has TWO green screws which must be for the EGC. Question is, should I pigtail a EGC wire via a wire nut joining the line and load EGCs so there’s a continuous EGC connection between line side and load side with the pigtail grounding the box via ONE of the green screws…OR…is fastening the EGC coming from the pump to one green screw, and the EGC to the pressure switch to the other green screw sufficient?
In the pressure switch, seems like it’s designed to be done the second way (no pigtail), since there’s very little room in the pressure switch housing for a pigtail, and TWO green screws are provided there as well.
I’ve only ever wired recepticles and switches with plastic boxes, where I always provide continuous EGC and also pigtail to the green screws on the outlet or switch. So the general question is, are metal boxes considered a sufficient EGC path?
Replies
First. I am not familiar with the term "EGC". GEC rings a bell as Grounding Electrode Conductor but that is a specific length of conductor between the meter, or first point of disconnects ground bar, and the grounding electrode, ground rod/s. I assume this is another term for a ground.
Most pressure switches have two ground screws. The steel base plate acts as a common two-slot lug. In most cases grounding through these two screws is perfectly adequate. As I understand it the plate and screw combination is certainly capable of handling the current. The fine thread screws have a lot of surface area in contact with the steel and the steel plate has a large cross section. In most cases I use them in this manner.
There is a condition that I will spend extra time and pigtail the connection in the pressure switch. That is when the pressure switch is in a location or situation likely to cause corrosion of the steel plate. Pumps in swimming pool or chlorinated water systems that are in the same building tend to cause metals to degrade over time. The same goes for fertilizers or manure, they need not contact the metal. The fumes alone will cause corrosion. If the steel gives up around or between the screws the connection will be lost.
In this situation I pigtail the connections with a good quality wire nut filled with a bit of Nolox to prevent corrosion of the spring. I also apply some Nolox to the screw hole before installing the screw and smear some of it on top of it when tight. The area is protected from rain or splash by the plastic cover so a bit of grease will last a long time. Should the steel base plate corrode away the connection will remain sound to the last. Yes, it is a bit tight in there but it is doable. Keep it neat and do yourself a favor. Keep some extra slack on all wires in the pump controller box so you have something to work with when the unit needs replacing.
4lorn,
Hey, cut johnnyd some slack...I knew he meant GEC, it's just that he's dyslexic.
I used to be also, until I got treatment. Now I'm K.O.!
Cliff
Glad to hear your K.O.
I thought I had cut johnnyd some slack. Even if he had used the abbreviation GEC it would still be wrong. A GEC, Grounding Electrode Conductor, connects directly to the grounding electrode, ground ring, Uffer ground, ground rod, etcetera. A GEC is a very specific and particular piece of wire that performs a narrow but very important function.
Not wanting to too directly point his inappropriate use of a term of art I tried, perhaps unsuccessfully, to limit it to a statement of basic definitions it an an attempt to make sure we where talking about the same thing. I had to make clear that I thought he was concerned with a simple ground connection so that he could discount my advice if I had misunderstood his post.
Other than that did you think I gave well reasoned and sound advice? Would you use some other method? If so what would you advise?
On that first post--where johnnyd uses "egc"--I took it to mean equipment grounding conductor. I've seen that acronym used before, and I think it's a generally accepted way--and a technically correct way--of referring to the ground wire (short of spelling out "equipment grounding conductor").
4lorn, your explanation of the GEC is, as usual, technically impeccable. No arguement from me there.
Cliff
Edited 4/26/2003 11:09:36 PM ET by CAP
Yep...that's what I meant, Equipment Grounding Conductor. Only trouble is, after wiring both pressure switch and control box...no water. When I connect the circuit via a disconnect "within sight of" the control box, I get the relay click and a slight hum (from the capacitor?), but no water. The well contractor said he will be out this week to trouble shoot...in the mean time, any suggetions for trouble shooting on my own?