@edifi @Amiers @FMEng @JD I've sorted at least 3 similar installations, on top of installations, added to previous installations in my area. Typically they've been installed by contractors, modified / improved by a second contractor years later, then expanded / improved by a third contractor. 'nough said.
Here's a common error I've uncovered in all 3 installations.
Often contractors have kept
track of the hot lines but lost
track of the neutrals.
I'll detail one example while the other installs in different buildings / nearby cities / by totally different contractors came down to the same root cause.
The installation I'll detail was a follows:
The group began with three 8
dimmer portable dimmer packs housed in a room adjacent to their booth.
The outputs of the packs were all 15 Amp 120 Volt parallel blade /
U-Ground industrial quality household connectors.
Female duplexes on the
dimmer packs and a row of male
tails neatly installed from individual cable grips hanging in a row from a length of covered trough.
Out in their
theatre, 8 circuits (#'d 1 - 8) hung as female
tails from a trough behind their
proscenium. A second group of 8 circuits (#'d 9 - 16) hung from a trough located as their 1st
FOH. The third group of 8 circuits (#'d 17 - 24) hung from a trough located as their 2nd
FOH.
So far, so good. All neatly installed, proper strain reliefs, covers closed, nice big yellow and black Brady labels. It all worked, nothing flickered and nobody got shocked.
Next step:
Two wall mounted 12 x 2.4 Kw installation racks were bolted to a back
stage wall with their outputs routed via
conduit to three locations back
stage. One 12
dimmer rack powered 12 additional
tails added within the existing 1 st electrics trough behind the
proscenium. The second 12
dimmer rack was routed via
conduit to a pair of 6
circuit boxes approximately 18" above
deck height on the
stage (rear) side of their
proscenium with one located SR and the other SL.
Next step: Someone decided the group should graduate from household parallel blade connectors to 20 Amp "old style" Twist-Locks. The group made this leap in the mid 1960's.
In the
dimmer room, they stayed with parallel blade
U-ground connectors as that matched their original 24 dimmers.
Out in their
theatre, they changed all of their connectors to the 1960's Twist-locks and changed all of the male connectors on their instruments from parallel blades to twists disturbing their
asbestos tails in the process.
Around about this
point, two problems began to
reveal themselves.
1; If all circuits were in use, things pretty much continued to work as anticipated.
2; If some circuits were unused and left hanging unplugged in their
dimmer room, two problems were noted:
a; Some circuits known to work were now no longer working; their males were plugged into dimmers known to be working but instruments known to be functional were no longer working.
b; Technicians were often receiving shocks from unused male connectors hanging disconnected from dimmers in their original
dimmer room.
CUTTING TO THE
CHASE:
Over the course of the 'upgrades / improvements' installers had kept careful
track of all hot conductors with regard to correctly numbering them BUT they'd lost
track of which specific white
wire was which figuring 'they're all neutrals, how can you go wrong'.
If / when ALL of your neutrals are terminating on your
neutral bar, odds are in your favor.
If / when you inadvertently have a
dimmer feeding out to an
incandescent lamp, passing through its 500
Watt filament and returning on the incorrect
neutral which is hanging, un-patched, on the wall of your
dimmer room you've got a live source on an un-mated male
connector just waiting to catch the attention of an innocent bystander.
Losing
track of the specific neutrals proved to be the root of the problems in all three installations I personally delved into sorting:
Different
connector types.
Different buildings.
Different cities.
Different contractors.
Different dimmers:
Strand,
ETC and Score Systems.
I'm not suggesting this is the problem in this case, only pointing out it's one possibility and quite time consuming to sort after the fact.
Toodleoo!
Ron Hebbard.
