Thread: fused main

2 400 amp fuses- 2 sets of 2/0 aluminum service cables- multi tapped in the service lugs.
Looks like it is over fused correct?

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Residential?

2/0 aluminum is rated for 150 amps. In parallel that would be 300 amps.

The question becomes, and you probably would not be able to read what is on the terminals without de-energizing everything, but you might also (should also) find in on the label, are those terminals rated for two conductors?

Some are, most are not.

Thus I would address it as two parallel 2/0 aluminum conductors for a combined rating of 300 amp which are two small for the 400 amp fuses which are installed, while correcting this, verify that the terminals are rated for two conductors, correct as required.

The other problem I see is only one neutral service entrance conductor for the paralleled hot service entrance conductors, there should be two neutrals, one run with each set of paralleled hot conductors. Is there another neutral service entrance conductor? if it is in the lower neutral terminal, where is the neutral for the feeder conductor?

In looking at the larger conductors going vertically on the left, I see four hots (two set paralleled) but only ONE neutral ... that does not bode well for what I think is there.

Are ALL those service entrance in one conduit? Then derating would also need to be done.

That photo just begs more questions than it provides answers to.

Yup. There is more there than the overfuse issue going on there as Jerry mentioned.

I can tell you with certainly that those terminals are NOT rated for two conductors. That is a biggie right there.

The lone neutral conductor is the other.

Is that a 3-phase commercial service?

Originally Posted by Speedy Petey

I can tell you with certainly that those terminals are NOT rated for two conductors. That is a biggie right there.

Peter,

How can you tell "with certainly that those terminals are NOT rated for two conductors"?

Is it because the two conductors are side-by-side instead of one-over-the-other?

Most terminals I've seen rated for two conductors were configured that the conductors fit into the terminal one-over-the-other.

However, the conductors could still have been installed side-by-side when smaller than maximum size conductors.

So ... what is the give away that you know those terminals are not rated for two conductors in each?

Time to gat some "Calibrated eyeballs."

I have not yet seen a lug rated for more than one 'not' wire under a screw; the multiple-wire lugs I've seen either have completely separate holes/screws for each wire, or a clamp that grips each wire separately from the other.

More important, that disconnect does not appear large enough to have a 400 apm rating.

Originally Posted by John Steinke

I have not yet seen a lug rated for more than one 'not' wire under a screw; the multiple-wire lugs I've seen either have completely separate holes/screws for each wire, or a clamp that grips each wire separately from the other.

John,

Same here for a long time, then I saw a photo of one which had an elongated terminal opening (not circular, more like two overlapping circular openings) which was rated for 1-2 conductors, maybe 1/0 or larger in size (don't remember those specifics).

Jerry, just experience I guess. I have seen and wired enough lugs like that to know that is a single wire termination. There is no way that one is rated for two. I'd easily bet money one it.

John, if the disconnect will accept 400A fuses it would have to be rated for at least 400A. There is no way you can physically fit 400A fuses into a 200A disconnect.

Originally Posted by Jerry Peck

John,

Same here for a long time, then I saw a photo of one which had an elongated terminal opening (not circular, more like two overlapping circular openings) which was rated for 1-2 conductors, maybe 1/0 or larger in size (don't remember those specifics).

Perhaps you're remembering these.

- Jim Katen, Oregon

Jim,

Thanks, that looks sort of like what I am remembering, what is the rating on those, I cannot read them in the photos.

Originally Posted by Jerry Peck

Jim,

Thanks, that looks sort of like what I am remembering, what is the rating on those, I cannot read them in the photos.

I am ashamed to say that I never made a note of the rating and I've since forgotten it.

- Jim Katen, Oregon