Control/Dimming Wire Woes/CD80 pack

[Lotos]

So, here I am, at work today... Doing some repair work in a Strand CD-80 Twistlock Dimmer Pack.
(Still waiting on parts for the Stagepin pack... Derek finally pointed me in the right direction for those...)
See here, for what I'm dealing with inside the CD-80

(Related: Does anyone else HATE the new Google Image Search?)

Those ceramic outlets on the pack I'm dealing with are damaged, and the wires are actually scorched... (Mostly damaged white ones... Neutral Conductor)

So, I call my local lighting supplier, order replacement ceramic sockets... Arrive at work today, and sit down to work...

Start replacing the ceramics, which come with wiring... And suddenly realize... "Crap, I have more damaged wire than I do damaged ceramics."
AKA, I don't need to replace the ceramics, just the wires.

Well, okay, I could steal the wiring off the ceramics, or I could buy some more wire... Easy choice, I love a trip to Home Depot anyway

Get to Home Depot... Now I'm looking for (bear with me here)
10AWG CL-1251; Tinned Copper; Extruded XLPE Insulation; 600v 125C

The closest Home Depot carries is 10/2 or 10/3 or 10/4 cable, which would be fine, I can seperate them out from inside the sheath... But no... These are 600v 90C... And the insulation is the wrong type... AKA: It gets hot, will melt, big fire, dimmer pack dies, I lose my job...

Fine, head back to work... Call my local friendly lighting supplier... He can offer me 10AWG wire, that's so old it has no CL listing... Well I sure can't use that... He can order me 250ft of the stuff I do need... But I need maybe 1/2 dozen 6inch linking wires... I thank him, and carry on my search.

Local electrical contractors... Can all offer me 10g SO (600v 90c) wire, or order me what I actually need... Again, a full spool of the stuff... A cost I simply can't justify to my department...

Getting frantic at this point, I speak to the Maintenance Department for the rest of the property. (Theatre Maintenance is done in-department)
He has a host of 10/4 which is no good to me, but he also has a 'magic account' with an electrical contractor.
He tells me "Just call him, let him know what you need, if we have to buy a spool, we have to buy a spool... Since it's my account, I guess I'm eating the cost."

So I call the contractor, let him know I'm looking for the hardest-to-locate wire in the Greater Toronto Area... He chuckles, takes down the specs, and says he'll call me back when he reaches the shop.

2.5 Hours later, now I'm just waiting for my phone to ring...

What a day.

 

[bishopthomas]

This is probably the most frustrating thing in the entire world for me. I absolutely HATE not being able to find simple supplies locally. Calling around trying to find expendables is so frustrating. I hate when I ask if they have something in stock and they reply, "No, but we can order it." So can I, and if I can get it through one of my regular distributors then I'll be paying far less for it, too. Being a small business myself I always try to help out the local guy, but if they don't have it then sorry... I'll pay a little more for the convenience of going to pick it up, but if I have to wait on UPS then I'll just call TMB or shop online. Keep us updated on your search.

(Related: Does anyone else HATE the new Google Image Search?)

I didn't realize there was a new one and briefly demo'd it just now. I think anything would have been an improvement over the old version and like this quite a bit. What issues did you have with it?

Easy choice, I love a trip to Home Depot anyway

Me too! I always peruse the tool aisle and find some kind of new and better tool than what I'm currently using. I was on a quest to find a good ratcheting screwdriver recently. Every time I went anywhere that carried tools I would take a walk down the screwdriver section.

 

[seanandkate]

Might this place be of any help? : SAYAL Electronics - Your Source For New And Surplus Electronic Components - We Buy Your Surplus!
It's one of my go-to places for hard to find stuff. I use the one in Thornhill, but there's one in Mississauga.

 

[mrb]

that is a specialty wire type used in the internal wiring of manufactured devices. You will never find it at home depot, an electrical wholesaler, or a contractor. The USA equivalent is AWM 3173. How much do you need? I might have some laying around I could mail you.

Also on a sidenote, dont take SO cord (or any other cable for that matter) and strip the jacket off to use the inner conductors. The cord is an assembly and the inner conductors are not suitable for standalone use.

 

[STEVETERRY]

So, here I am, at work today... Doing some repair work in a Strand CD-80 Twistlock Dimmer Pack.
(Still waiting on parts for the Stagepin pack... Derek finally pointed me in the right direction for those...)
See here, for what I'm dealing with inside the CD-80
(Related: Does anyone else HATE the new Google Image Search?)

Those ceramic outlets on the pack I'm dealing with are damaged, and the wires are actually scorched... (Mostly damaged white ones... Neutral Conductor)

So, I call my local lighting supplier, order replacement ceramic sockets... Arrive at work today, and sit down to work...

Start replacing the ceramics, which come with wiring... And suddenly realize... "Crap, I have more damaged wire than I do damaged ceramics."
AKA, I don't need to replace the ceramics, just the wires.

Well, okay, I could steal the wiring off the ceramics, or I could buy some more wire... Easy choice, I love a trip to Home Depot anyway

Get to Home Depot... Now I'm looking for (bear with me here)
10AWG CL-1251; Tinned Copper; Extruded XLPE Insulation; 600v 125C

The closest Home Depot carries is 10/2 or 10/3 or 10/4 cable, which would be fine, I can seperate them out from inside the sheath... But no... These are 600v 90C... And the insulation is the wrong type... AKA: It gets hot, will melt, big fire, dimmer pack dies, I lose my job...

Fine, head back to work... Call my local friendly lighting supplier... He can offer me 10AWG wire, that's so old it has no CL listing... Well I sure can't use that... He can order me 250ft of the stuff I do need... But I need maybe 1/2 dozen 6inch linking wires... I thank him, and carry on my search.

Local electrical contractors... Can all offer me 10g SO (600v 90c) wire, or order me what I actually need... Again, a full spool of the stuff... A cost I simply can't justify to my department...

Getting frantic at this point, I speak to the Maintenance Department for the rest of the property. (Theatre Maintenance is done in-department)
He has a host of 10/4 which is no good to me, but he also has a 'magic account' with an electrical contractor.
He tells me "Just call him, let him know what you need, if we have to buy a spool, we have to buy a spool... Since it's my account, I guess I'm eating the cost."

So I call the contractor, let him know I'm looking for the hardest-to-locate wire in the Greater Toronto Area... He chuckles, takes down the specs, and says he'll call me back when he reaches the shop.

2.5 Hours later, now I'm just waiting for my phone to ring...

What a day.

When you get your wire, you may want to consider a different wiring scheme than the creative one in the photo. I see only three neutral conductors servicing 24 outlets, which is why you have burned conductors. I suggest wiring a single neutral conductor to each pair of outlets. Are these 1200W or 2400W dimmers?

ST

 

[jstandfast]

Having a great deal of rental shop time; in charge of a large pile of CD-80 packs, I gotta ally myself with every word of Mr Terrys' post. That wiring configuration in your picture
is a trainwreck that hasn't happened yet........

 

[STEVETERRY]

Having a great deal of rental shop time; in charge of a large pile of CD-80 packs, I gotta ally myself with every word of Mr Terrys' post. That wiring configuration in your picture
is a trainwreck that hasn't happened yet........

Err...the train wreck actually did happen--hence the burned outlets and neutral conductors!

ST

 

[ship]

burned neutral conductors often due to unbalanced load - something to watch and work on. This if not loose terminals also to ensure it's not the case on other racks.

Type MTW wire inside a rack should be sufficient replacement and easier to find. Do not use type SO or other types inside a rack.


On the other hand in buying a spool... if you find this problem once and especially twice, it's probably systemic. Stocking a spool of wire is very useful and isn't going to deteriorate thru the years. I literally have a wall of wire spols and more in use. Very useful.

 

[mrb]

burned neutral conductors often due to unbalanced load - something to watch and work on. This if not loose terminals also to ensure it's not the case on other racks.

Type MTW wire inside a rack should be sufficient replacement and easier to find. Do not use type SO or other types inside a rack.


On the other hand in buying a spool... if you find this problem once and especially twice, it's probably systemic. Stocking a spool of wire is very useful and isn't going to deteriorate thru the years. I literally have a wall of wire spols and more in use. Very useful.

regular MTW (UL 1015) is 105c PVC insulation. The wire he needs to replace is 125c cross linked polyethylene which is much better for higher temp applications such as inside a dimmer. I dont recall seeing PVC wire inside a dimmer....

 

[ship]

Fair enough and time for ETC rep's to chime in for me in bad jujo. SF-2 work ok instead?

 

[jstandfast]

Err...the train wreck actually did happen--hence the burned outlets and neutral conductors!

ST

We differ in terms I think. The posters' photo shows some troubles no doubt,
and certainly a maintenance problem too ( how many more has he got wired like that ?).
By "Trainwreck" i was referencing the next level in the cascade: the resultant fire,injuries,
lawsuits,etc.

 

[Lotos]

Well... I'm now the proud owner of a 76m spool of this stuff... And in the process of replacing burned leads.

Re: The wiring schematic in the photograph... All my packs are wired this way, in fact every CD-80 Pack I've ever opened has been wired this way... I've never actually seen any scorched as bad as the one I had to open (and I'll explain that in a second...).
With due respect to steveterry, and other members... I will be repairing this one to 'Factory Spec' as it were, and maintaining the 'daisychained' Neutrals.

Re: The damage to this particular pack... Our current show has the entire rig operating at 80% for close to two hours straight... Not only is this killer on Gel, but a lot of these dimmers are loaded at 2k... Which was within their spec... When they were manufactured... (This one has a QC tag from August 16th, 1989)
However, when I handed off the patch sheet to my crew after hang was complete, I neglected to spec how the dimmers should be patched... And in an effort to save cable, wherever two fixtures were patched to a single dimmer, the two-fered into a single of the dual female twislocks.
(This is a 12 channel pack, offering 2x 20A Twistlock Female Receptacles per Dimmer)
What this created, above anything else, was heat at the connection points.
Once I paired the 'patch' down, running loads out of both Receptacles, the heat disappeared... The damage was already done however. Interestingly, out of 5 scorched females, only one actually failed.

Anyway, long story short... I finally found an electrical contractor who (a day and a half later) was able to get a spool from his supplier... (Tevelec, located within spitting distance of my theatre...) for less than my RFQ came back from Tevelec directly for. I've got more than I'll ever need or use... But I've got the right wire for the right job.

As for the loading... We very rarely push these packs to their limit, simply due to their age, and our abundance of dimming... We'd paired loads up for this show, simply to keep one pack out of service so we could 'swap' loads around, and do maintenance on the packs individually...

Ironically, the fact that we'd set things up so we COULD do maintenance, causes us to NEED to do more than we'd intended.

Live and learn.

Edit, to be clear: Never with any seriousness did I consider using SO wire inside these packs. The XLPE sheath is there for a reason... In cases of high heat (what this pack underwent) it simply bakes and flakes off... Instead of melting, or worse, burning.

Thanks for all the replies folks! I suppose, in retrospect, this probably should've been posted in Punching Bag... But I thought it might spark some interesting discussion here regarding types of wire, and indeed it has!

 

[Lotos]

Might this place be of any help? : SAYAL Electronics - Your Source For New And Surplus Electronic Components - We Buy Your Surplus!
It's one of my go-to places for hard to find stuff. I use the one in Thornhill, but there's one in Mississauga.

Actually, first place I checked, as they are literally 'right next door' to my space... But alas, not to be found.
I did pick up the spade crimps I needed for another project, while I was there however!

 

[seanandkate]

Actually, first place I checked, as they are literally 'right next door' to my space... But alas, not to be found.
I did pick up the spade crimps I needed for another project, while I was there however!

I can be a seriously dangerous store that way . . .

 

[JD]

Odd... A properly designed pack should be able to handle any and all imbalanced loads without damage. I don't understand how they went into production with that layout.

 

[Lotos]

Odd... A properly designed pack should be able to handle any and all imbalanced loads without damage. I don't understand how they went into production with that layout.

The damage was caused by heat in the external male connector. (The Twofer) causing heat to build up in the female connector in the rack, and char the neutral wire.
Likely dirty connectors, or imperfectly mating connectors...

I'm certain this is the point of damage, as the wire connections further down the line (where they should be taking MORE load, and thus more heat, if the neutral bus was at fault) are fine...

I personally don't see the big issue with the layout...
Of the 8 connectors per-neutral bus, each are shared dual-style on a 2.4k output.
That's only 4x 2.4k circuits per bus...

 

[JD]

If there are 4 2.4k dimmers on each neutral, then (at best) at least one phase leg is represented twice, indicating a potential 40 amps through #10 wire. This also ignores potential neutral over-current that occurs on phase chopped dimmers. None the less, rules change inside a sealed "designed" unit that has approved code coverage. Your post sounded as if you were also seeing conductor damage away from the connectors.

 

[Lotos]

If there are 4 2.4k dimmers on each neutral, then (at best) at least one phase leg is represented twice, indicating a potential 40 amps through #10 wire.

Not so, my apologies, I thought I mentioned this sooner... What is easily apparent to me from the photograph may not be apparent to others less familiar with the CD-80 Interior. (Besides, since this is a stock photo, not of my own rack, assumptions can run wild!) I'm working on a 12x 2.4k Dimmer Pack. Each Phase powers 4 of the 2.4k dimmers.

None the less, rules change inside a sealed "designed" unit that has approved code coverage. Your post sounded as if you were also seeing conductor damage away from the connectors.

Hence my desire to restore things to 'Factory Spec' as it were... Apologies for not being so clear in my opening post... I hadn't quite forseen the discussion becoming this in depth

There are two conductors that are completely missing their insulation... These two were both connected directly to the Neutral of the most damaged outlet. The one that caused me to take this pack out of service initally (after having to forcibly remove the male connector from the socket.) Aside from that the heat damage is localized to the 1/4" or so of insulation adjacent to the screw terminals. (There is also heat damage to be seen on the screw terminals themselves.)

Apologies again for not being quite so clear in the first place But I must say, I'm enjoying the discussion this has (pardon the pun) sparked. I'll try and remember my camera on the way to work tomorrow, so I can snap a picture of the repaired panel, and highlight what occured.

 

[STEVETERRY]

JD is right. Let's do some math here:

12 x 20A dimmers = 240A total

4 x 20A = total load per each of the three neutral conductors

Assume best case that three of the four dimmers are on different phases. In that case 20A (max imbalance load) x 1.30 (non linear load ampacity adjustment)=26A

Now add the fourth dimmer, which is a straight imbalance: 26A + 20A =46A

Now, it is entirely possible that a #10AWG 125C conductor could handle 46A to UL's satisfaction. Here's the problem: the outlet terminations are rated at 60C, and they are used as part of the daisy chain.

While the CD-80 pack is a venerable example of portable dimming, this neutral daisy chaining is an extremely marginal design, and one that can be easily improved by wiring a single neutral conductor to each pair of outlets on a dimmer, as long as you're in there tearing out burned wires and outlets. After all, there's a reason they burned, and I don't buy the male plugs as the culprit.

ST

 

[STEVETERRY]

We differ in terms I think. The posters' photo shows some troubles no doubt,
and certainly a maintenance problem too ( how many more has he got wired like that ?).
By "Trainwreck" i was referencing the next level in the cascade: the resultant fire,injuries,
lawsuits,etc.

Point taken. For me, the trainwreck is the marginal design of the neutral conductors.

ST