Bjarney's message caught my eye, and I wanted to add to it.
With the screwy "two-row" bus arrangement in Zinsco plug-in
panelboards—that was fine for 120/240V 3-wire systems, but for
3ø, the bus bars literally had to be "braided" to match 3ø up with
the needed two rows of bus stubs. If you ever saw one, it was
unforgettably weird looking. What a mess.
And, along the lines of Mamills' reply regarding the 3Ø Zinsco Bus:
Bjarney (and others): I remember seeing several of those Zinsco
load centers about 30 years ago being installed in a church. It
really was a weird bussing arrangement... three busses, covered
with some type of thermoplastic insulation, I guess - black, red,
and blue, that looked like it was literally woven into place. If
memory serves me, the breaker jaws only had to be set in one
position (they are removable in order to tap one or the other buss
in a 1 phase setup, of course) in order to pick up each of the
three phases.
I have dealt with quite a few of 3Ø Zinsco Subpanels with the mentioned type of Plug-On Bus Kit.
A "Weaved" and "Color-Coded" Bus is the best description that could be made!
The way the Breaker's termination stab(s) are positioned to terminate across opposite Phase Bus tabs was done by physically unscrewing the termination on the frame, then flipping it backwards from its current position.
Even more of an oddity was the 3Ø Split (or Dual) Bus type Subpanels. These had two seperate Bus Kits inside of one Enclosure (they were both the same type of "Weaved And Color-Coded" Bus Kits).
This resulted in a Zinsco Subpanel which had the similar "Left-Right" Breaker Spaces of other Panelboard types.
As known, the normal Zinsco layout has one "row" of breaker spaces - and if you number the circuits, they would go in step - "1", "2", "3", "4", etc. All on "One Side" (actually, there's only one row, so there is no real "Side" to reference!).
On the before mentioned Panel, the dual bus kits resulted in "Left: Odd, Right: Even" circuit numbering of spaces - similar to the "Normal" breaker space layouts of other brands.
(BTW: There were other makes of Panelboard Bus Kits with a single row setup. Square D's "XO" Panels are one such brand).
As to the rant about the Zinsco Plug-On Bus termination, I have thought the same as Bjarney!
Mike — You nailed the description exactly. “Q-frame” was the
one—I forgot about those triple-cheesy ‘swing-around’ bus clips.
If aluminum bussing ever had a hope for switchgear, Zinsco did
their level best as a prime example of how NEVER do it. They may
have well been in cahoots with a few fire-insurance carriers for
the extra premiums.
Have dealt with SOOOOOOOO many fried terminations on misc. 225 Amp - 400 Amp sized Zinsco MCCB Frames, which were Plug-On.
Not all Manufacturers Plug-On frames are Immune! - Replaced lots of other brands too, just seemed to be a much higher percentage of Zinsco's (also, they were in Commercial Enviroments..the Zinscos and the others).
One particularly irritating event was during an Active Bank Branch remodel (Keep the Bank in full operation, remodel the entire building "around them").
Switch gear for both systems was Zinsco, and used Plug-On Busses.
(older area and building - services fed from a 4 wire Delta. One 3Ø service section, one 1Ø service section)
1Ø Gear Section had two - 200/2 frames, along with a few smaller ones. The 200/2's fed heavily loaded Subpanels.
During the preliminary stages of the remodel, odd behavior was observed in the operation of the existing Indoor Lighting - Transient dimming, fixtures going off then on; along with Motors running sluggish (bathroom exhaust fans).
Contactors of the EMS Control Panel I had installed previously were also effected - and were randomly opening and closing rapidly.
All these loads were on the same Subpanel.
Since we needed to keep the Branch in full operation (we worked the crucial remodel stuff during the branches "Off-Hours"...AKA Night Work!), and the problem had become increasingly worse over a 4 day period, it was agreed that I would shoot trouble on this ASAP.
Checked the entire Subpanel, found nothing wrong! (Subpanels just happened to be right next to the gear, too!).
Suddenly as I was replacing the Dead-Front, the lights started freaking out again - and the Subfeed Breaker was buzzing like crazy!
A simple Inspection of the breaker revealed the problem!
Next Evening after the branch was closed, I replaced the breaker + cleaned up the bus kit.
When I tried to unloosen the lugs for the Subfeed Conductors, the entire frame disintegrated in front of me!
Had things back up in about 1½ Hours.
No problems on that Subpanel after that.
Next one to fail was the Subpanel with the Computer Equipment on it!!!
About 10 days after the first scenario was rectified, it hit again - this time the problem was causing a greater deal of bad stuff!
Again, transient losses of power were experienced on...of course, ½ the computers each time! The server equipment was on UPS, which the power loss alarm could be heard once in a while.
The other affected Subfeed frame was located at the Upper Right of the bus kit, and this one was at the Lower Left.
I troubleshot the situation - except this time, began at the Gear.
Sure enough, the exact same thing was happening here, and the frame also disintegrated upon loosening the lugs.
Prior to final commissioning, both bus kits on both Gear sections were replaced, along with the remaining existing frames. (Bank's Const. & Dev. staff weren't hesitant in the least to authorize this C/O!!!)
They had sent numerous techs out prior to the remodel to fix the problem (staff calls for service), along with sending out IBM to verify things on the machines.
Can only imagine the money lossed on this!
Losses from the service calls, the IBM support calls, the loss of data, all that stuff!
Having dealt with these types of situations really drives home the idea of NOT using Plug-On devices in Designing of Electrical Systems for Commercial Enviroments!!!
Hope this story is enlightening and interresting!
Scott35