3

This is in Guatemala, in a semi-rural area, so there are no codes as such to be followed. Also local electricians are mainly DIYers like me, so I haven't gotten much consistent help there.

I have the power connected to a meter on a post by the property edge, this was done by the power company and has the earth (copper bar) and neutral connected inside a small box in the post. There is a 50 amp breaker on the hot wire. From this post, there is a 22 meter run of #6 cable to the house, neutral and hot wires only. This is going underground, and can't be changed easily. At the house there is a panel with slots for four breakers only, which will do as it's a small weekend house.

I plan to connect a copper bar earth at the house, my question is should the earth bar be connected to the neutral bar? The panel has an aluminium jumper to connect the two, if I should. I have read that in the US sub panels must not have the earth & neutral connected, I'm not sure if this counts as a sub panel or not.

It's a single 120v supply, i.e. two wires only, but I want to put earthed sockets in the house. The earth from the house panel will be 20 meters away from the earth at the power supply post, if that makes a difference.

Thank you for your attention.

Improve this question
9
  • 1
    I am going to weigh in even though I'm not an expert. I think you want to bond the house ground to the neutral bar in your panel. The reason is you want a low resistance connection of the earth (ground) conductor in the house so that if the ground wire would become hot, a high current would flow and would trip the breaker immediately. If you did not bond the ground and neutral, you would depend on enough current flowing through the ground back to the meter to trip the breaker. The resistance of this ground path might be high enough to limit the current below the limit of the breaker.
    – Jim Stewart
    Commented Apr 16, 2018 at 21:05
  • 1
    Is the transformer on that pole? @isherwood neutral is grounded in two places, the other being the transformer.
    – Harper - Reinstate Monica
    Commented Apr 16, 2018 at 21:38
  • What make and model is the breaker at the pole, and what make and model is the panel at the house?
    – ThreePhaseEel
    Commented Apr 16, 2018 at 22:35
  • To Jim Stewart: I was thinking along the same lines, but not sure.
    – Mike B
    Commented Apr 16, 2018 at 23:13
  • To Harper, I don't think the transformer is near the pole, there are two wires coming off the mains into my meter then inside the post where the breaker is, plus an earth wire coming in and connecting with the neutral at the meter. The power company connected these up like that.
    – Mike B
    Commented Apr 16, 2018 at 23:15

2 Answers 2

Reset to default
2

Better idea -- move that 50A breaker to the box, and put a non-fused safety switch at the pole

What you can do instead of having the redundant neutral/ground bonds at the pole and the house is:

  • Have the utility cut the power
  • Move the 50A breaker to the box on the house as it'll be the house main breaker. Remove the box from the pole.
  • Put a 2 pole, non-fused, outdoor type (NEMA 3R enclosure) safety switch (UL98 listed, with a minimum fault current rating of 10,000A and a minimum working current rating of 50A) in place of the box on the pole that had the 50A breaker there. Siemens, GE, Square-D, and Eaton all make quite suitable units, although they won't exactly be cheap.
  • Land the hots on one pole of the safety switch, and the neutrals on the neutral/grounding block in the safety switch. Torque all connections to spec, and make sure that any grounding electrode wires at the pole that went into the old box go into the neutral/grounding block on the safety switch. You will need to make sure this block is bonded to the enclosure as well.
  • Put a "METER DISCONNECT -- NOT SERVICE EQUIPMENT" label on the safety switch (inside cover is good, but don't put it over the existing labeling there).
  • Have the utility turn the power back on

This is a hot sequence meter disconnect as per NEC 230.82(3), and provides the best of both worlds:

  • You can cut off power to your house completely at the pole, allowing you to work on the box on the house safely
  • The neutral-ground bond, though, can still live at the house, allowing that to be the main panel, and allowing you to safely use the existing ungrounded feed from the pole.
Improve this answer
0

I finally got to the point of connecting up some sockets, and what I did was connect the earth and neutral bars with the jumper, then connect everything up, and checked the plugs with a plug-in circuit tester and everything came up good first shot, so the suggestions above were correct, and the two bus bars are connected.

Improve this answer
6
  • This doesn't address the situation of where that neutral-earth bond should be -- right now, I suspect you have a duplicative bond in your system, which is NFG. See my answer for a (not terribly cheap, but workable) way out of the situation without re-running cables, though.
    – ThreePhaseEel
    Commented Jun 6, 2018 at 2:29
  • @ThreePhaseEel There is no parallel ground path, so the main hazards associated with multiple earth-neutral bonds is gone. What OP wants to do would be compliant under NZ codes, so IMHO isn't an extremely serious issue, merely a nice-to-have - and sockets/power at the meter location would also be nice, potentially.
    – SomeoneSomewhereSupportsMonica
    Commented Jun 6, 2018 at 2:36
  • @SomeoneSomewhere -- the fault impedance for that main breaker to work against is awful though -- I suspect the main reason what you're talking about (which is basically a TT configuration) is allowed in NZ codes is because the main is a RCD in that setup.
    – ThreePhaseEel
    Commented Jun 6, 2018 at 3:20
  • Nope, no TT, no main RCD. I'm suggesting that you treat the meterbox as the main switchboard (MEN link, main switch etc.), then take a two-core to the house, and treat it as an outbuilding with a phase conductor and PEN conductor. So a separate earthing system in the house, with its own MEN link. No RCD (beyond those required for individual circuits).
    – SomeoneSomewhereSupportsMonica
    Commented Jun 6, 2018 at 3:30
  • @SomeoneSomewhere -- ah, then TN-C feed -- this is considered obsolete in the NEC.
    – ThreePhaseEel
    Commented Jun 6, 2018 at 20:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.