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I have setup on building where panel is feed from meter through disconnect. The wire is #8.

There are two legs and a ground coming from meter. There is a ground wire running to metal case of disconnect. But there is only two wires running entering conduit with NO neutral.

These wires run 70 feet into building to subpanel which is 1950 era.

Questions:"

How is this type of system able to work?"

What is theory of this old type of panel?

Do I need to run a neutral wire from disconnect to panel? (I want to upgrade.)

Diconnect at Meter

Panel Inside Building

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  • It looks like the panel only feeds line-to-line (240v) loads, no neutral is needed. If it is powering 120v circuits then it is flowing current on the conduit. – NoSparksPlease Dec 13 '20 at 19:11
  • What loads does this subpanel feed, where does the double-tap from the subpanel lugs go, and what size is the condut going out to the subpanel? – ThreePhaseEel Dec 13 '20 at 20:31
  • Also, can you get us a clear shot of the front of the meter please? That might offer a few clues here – ThreePhaseEel Dec 13 '20 at 20:31
  • Not actually related to the question but what is going on with the fuse socket on the bottom left of the second image? Is it a melted penny or copper foil in place of a proper fuse? – mikes Dec 13 '20 at 20:47
  • @mikes bottom left has a fuse in it, bottom right has (nonconductive, I presume) rubbish in it – ThreePhaseEel Dec 13 '20 at 20:51
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No neutrals.

My first reaction is "they played "fast and loose" with the differnce between neutral and ground. Neutral is not ground. However, I don't see any neutrals at all in the photographed fuse box. It looks like this panel is for 240V loads only. (baseboard heaters would be my wild guess; can't be a range or dryer, those need neutral). Water heater maybe.

As long as all loads are 240V only, I'm OK with the 2-fuse disconnect since 240V-only loads don't need both legs to trip out on a failure. However split-phase loads (a 120V subpanel, washer, dryer, MWBCs) do need common trip to avoid a variety of badnesses. So if you plan to add circuits that use neutral, you really need to change that master disconnect/fuse box out to a breaker. The usual manufacturers make a variety of "breaker disconnects" (basically a 2-space service panel) or you could fit a small main panel there and have some extra breaker spaces. However it'd need to have a distinct main breaker.

Here's how it ought to be done.

Safety Ground, or its legal name is "the Equipment Grounding Conductor", must originate at the first disconnect switch from the meter. The takeaway here is that the power company does not supply ground, and so you don't bring ground from meter to disconnect.

Actually, you bring it the other way; the meter pan is grounded from the main disconnect; but that happens via the metal conduit. Done and dusted.

The meter to disconnect wiring is correct.

The "Grounding Electrode System" is the wiring from your main disconnect to the ground rods or water pipe or Ufer that actually provide the contact with the earth. The GES should come into this disconnect box. This is also the one place in the system where it should be tied to neutral.

Beyond this main disconnect, both hots and neutral must be carried as insulated wires to the "main" subpanel, which is a subpanel because it is downline of this point.

By modern Code, ground and neutral must be carried separately from here to there.

Archaic Code allowed the subpanel to be grounded to the neutral wire. The neutral wire could even be bare, as it typically was with pole lines. However, the neutral wire would never, ever be carried as the metal of a conduit pipe! That was illegal the day it was installed.

More notes

Note how your feeder to the first subpanel "daisy chains" - it is then carried onward with more #8 wire to anther subpanel. That is fine, but you need neutral there too.

Note that your existing #8 wire is TW type, which is limited to 60C per Table 310.15(B)(16). That means your #8 is only good to 40A. If that wire were THWN, it's good to 90C so the limiting factor becomes the lugs on the fuse boxes. If their labeling is intact and blesses 75C operation, then it's worth changing the wire to THWN so you can up-fuse from 40A to 50A.

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  • Okay .. I have run a neutral wire from meter to panel and everything is working good on my system . Now My next question is about bonding neutral to ground. Do I do this at meter or at the panel some 70 feet from meter. And how do I bond at either place. – Herb1960 Mar 30 at 19:35
  • @Herb1960 Like I say, the neutral-ground bond is at the first disconnect past the meter. That appears to be right next to the meter, so there you go. Ground bonds and ground rods there. Ground wires from there on. If the other end of the run is a separate building, ground rods also in addition to the ground wire. – Harper - Reinstate Monica Mar 30 at 19:56
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It kinda looks like the way it's wired if it's fed with 240 volts then 240 volts will be on each of the 3 circuits. They may have fed 120 volts to that fuse box and fused both the hot and neutral.

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  • I appreciate all y'alls feedback. – Herb1960 Dec 14 '20 at 21:34
  • I appreciate all y'alls feedback. I have added a couple of pics showing meter and labeled panel.So it appears that they are using conduit neutral source. The outlets in space were the old two prong fashion with no ground.So to bring it up to code, I need to run another wire for my neutral. And change panel. It is not obvious in my pic, but the A/C blower comes off the main lugs down to a small breaker in separate enclosure. But Flex cable comes out of panel and runs to lights. So I know the metal conduit was used in the past as the neutral connection. But that is outlawed now. Correct? – Herb1960 Dec 14 '20 at 22:55
  • To continue, If metal shielding is used as the neutral wire, hiw did it get to neutral prong of receptacle. Just an thought. – Herb1960 Dec 14 '20 at 22:57

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