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Joined: Oct 2000
Posts: 2,749
Sent from the field:

Here is a picture of a 1600 amp transfer switch that was wired a little too neatly.

How it ever got past an inspector is way beyond me! Luckily the load is no where near capacity and nothing has gotten hot – yet!

[Linked Image]

There are two identical transfer switches side by side wired the same way nearby in San Jose.

One is for HVAC, and the other for the UPS, DC plants and other technical loads. The transfer switches, and switchgear were installed with a permit and inspected by the city.

The site manager tells me that the electrician that installed it now is an instructor at a junior college, and wanted to bring his class to the site to see the installation!

I am presently trying to figure out a way to wire them correctly, and keep the site on line at the same time.


Joe Tedesco, NEC Consultant
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Joined: Jan 2005
Posts: 5,422
Likes: 1
Cat Servant
In a pic so neat, it's hard to see what the fuss is all about. All those black wires kind of blend together, you know!
It it as I suspect- that each phase has its' own conduit?

Joined: Oct 2004
Posts: 806
I agree with reno, it sure looks like each phase has it's own private conduit!!

Too bad such clean workmanship is fouled up by such an error!

As for the AHJ missing it, it's not impossible. As was explained to me, the AHJ (intentionally or otherwise) will tend to make the depth of his/her inspection based on the workmanship of the site. Really neat work would tend to get an inspection not subject to the "fine-tooth comb." Not-so-neat work would make for a deeper inspection to see if there are issues hidden within. Still, one would hope the AHJ in this case is aware of a little thing called induced current!

Gregg, I too am wondering how you could possible correct this and keep the site on-line. When you figure it out, please share (and maybe post "after" pics?) [Linked Image]

My original thought was to correct the genny side first, transfer to genny power then fix the utility side. But one small (sarcastic) flaw with my idea is that the load side connections left alone would make for a phase-to-phase short if left as-is? And of course, how would you correct the load side if it had to stay fed? Hmmmm...

How about making temp hook-up directly from utility side to switchgear, (at 1600 amps no small feat), correcting the transfer switch then re connecting?

Wow. Now I remember why I stick with cinema stuff. [Linked Image]

Stupid should be painful.
Joined: Oct 2004
Posts: 265
Is that supplied by 1600A? That doesnt look like 4 500MCM on each phase to me.

Joined: Feb 2005
Posts: 219
HOLY CRAP!!!!!!!

This looks like a new install.
There is no statuate of limitations on code and this contractor needs to be stopped!

Hopefully he is a Janitor at a JC

[This message has been edited by sierra electrician (edited 06-13-2005).]

Joined: Jun 2005
Posts: 2
Junior Member
Yes, indeed all of the phase conductors go through the same conduit. And to top it off, there are two matching transfer switches both wired this way in the same electrical room. When you are on a roll.... There are also grounding and ground bonding issues, as if that would surprise anyone reading this.

The solution is to bypass one transfer switch by using the other, since the load is still minimal by backfeeding breakers in the distribution panels that are adjacent to the transfer switches. Then pull out wiring as necessary and re-feed new, the correct way.

Joined: Nov 2000
Posts: 2,148
Is that supplied by 1600A? That doesnt look like 4 500MCM on each phase to me.
Four sets of 500kcmil is not enough copper for a 1600A circuit.

Joined: Oct 2004
Posts: 265
Actually, what size would be needed for 1600A? I always thought parallel runs were based on amperage, but I looked it up and its based on cross sectional area (ashamed to admit that all my parallel runs were engineered and I never bothered to look it up =\). I have no idea what cross sectional area is needed for 1600A.

I would assume 600MCM would be enough since the divided rated amperage would be enough, but the cross sectional area for that high of amperage is throwing me off.

[This message has been edited by dmattox (edited 06-14-2005).]

Joined: Sep 2003
Posts: 650
IMHO no need to be quite so harsh on this guy. My read of the pictures (and thus insufficient data) is a fine electrician who had a _serious_ brain fart.

The neat workmanship suggests that sort of pride that comes of wanting to do a good job, and the mistake was one that was missed by the inspector as well. In fact, I'd bet that this installation is reasonably safe because all of the bonded connections are probably made up perfectly, and can thus carry the induced currents without excessive heating. Not to say that this shouldn't be fixed, nor that the original electrician shouldn't be learning a costly lesson...just that this is probably a fine guy who should be more than welcome in this forum, and that this is an expensive mistake that would be appropriate in


Joined: Nov 2000
Posts: 2,148
Parallel ampacity is based on the sum of the individual conductor ampacities, but the ampacity of 500kcmil is 380 amps, not 400.

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