Control/Dimming Electrical Connection for a Dimmer Rack

Now, please correct me if I am wrong, but I believe that it is against code to just build an adapter to go from a multi-pole connector to multiple single pole connectors without some kind of junction box. Once again, this is something to CONSULT A QUALIFIED ELECTRICIAN on.

Could you please quote the regulations on this? Because I know of at least 2 rental houses (ALPS and High Output) in my area that have provided me with just such an adapter per my request several times. We used a NEMA 14-50R to Cam-Lok adapter for two of our Ballet performances at separate times. It was just a straight NEMA 14-50R to 1/0 Gauge Wire w/ Cam-Lok tails. It looked safe, there was no exposed wire and it had proper strain relief as well. I also know they provide other NEMA to Cam adapters just like this in all sorts of configurations.
 
Could you please quote the regulations on this? Because I know of at least 2 rental houses (ALPS and High Output) in my area that have provided me with just such an adapter per my request several times. We used a NEMA 14-50R to Cam-Lok adapter for two of our Ballet performances at separate times. It was just a straight NEMA 14-50R to 1/0 Gauge Wire w/ Cam-Lok tails. It looked safe, there was no exposed wire and it had proper strain relief as well. I also know they provide other NEMA to Cam adapters just like this in all sorts of configurations.

Again, this is something that could vary from state to state, I haven't done a ton of research on it, so again, please feel free to correct me. What you are not supposed to do is make what is known as a cam-lok splay. If you have a multi-conductor cable you are not supposed to connect one end to a multi-pole connector and then connect the other end of the cable to single pole connectors like cam-loks without some kind of enclosed wiring device like a junction box.

Why? Because multi-conductor cable is intended for use with multi-pole connectors, not single pole connectors. Making an adapter using multi-conductor cable means that you would have to strip away the more robust outer jacket of the cable and when you attach connectors to the softer inner jacket there is much more potential to damage the jacket. Doing this may also cause exposure of the inner jacket to harsher conditions than it is intended for, anything from UV rays to water.

It sounds like the adapters you have been given as parts of rental packages are OK because it sounds like they use single conductor cable from the multipole-connector to the single pole connectors. As long as each conductor is an individual unit with it's own inner and outer jacket it should be OK. I may have been a little too general in my previous post, I was just trying to stress the importance of making sure that the OP got professional help.
 
Ah, yea I can now see where the mix up was. Yes, the adapters I used were not multi-conductor cable but just 4 single-conductor cables feeding into one giant 14-50P Connector. I can definitely see how stripping the outer jacket off a multi-conductor cable and splaying the ends would be hazardous, but no, the one I used was 4 separate 1/0 gauge SOOW conductors going into one 14-50P connector.
 
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Ah, yea I can now see where the mix up was. Yes, the adapters I used were not multi-conductor cable but just 5 single-conductor cables feeding into one giant 14-50P Connector. I can definitely see how stripping the outer jacket off a multi-conductor cable and splaying the ends would be hazardous, but no, the one I used was 5 separate 1/0 gauge SOOW conductors going into one 14-50P connector.
In that case, one must ask the question of whether the strain relief of the 14-50P connector is designed to accept five separate 1/0 gauge SOOW conductors. (And seeing as how the NEMA 14-50 is a 125/250V device,
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wouldn't it only be four conductors?)
 
Sorry to hijack here, Sony, are you in Massachusetts?

I'm from Massachusetts but I go to school in Rhode Island so thats where I am right now.

In that case, one must ask the question of whether the strain relief of the 14-50P connector is designed to accept five separate 1/0 gauge SOOW conductors. (And seeing as how the NEMA 14-50 is a 125/250V device,
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wouldn't it only be four conductors?)

Sorry, you're right it was 4...I'm just so used to working with 3 Phase I just automatically say 5. I edited it thanks, and as for the strain relief...I don't know, they gave me the connector and I used it, it seemed pretty secure at the time. The connector was a monster, it seemed bigger than any other 14-50P connector I've used before and it wasn't deformed at all even with all those cables stuffed in there. Again...I don't know if it was up to code but it looked and felt safe to me.
 
I made one or two of those, and they seem perfectly safe and follow code. Yet i have been to venue's that have these connectors, but then you can ask for their electrician and typically if a disconnect is feeding those, their electrician will be more than happy to tie your tails in instead, and i have been in several places where they have 3 phase in the disconnect, but are only pulling two hot legs out. Also commonly the box is derated down to 50A for the plug, but they will slap in some 100A fuses (of course the wire and breaker feeding the disconnect is rated for at least 100A) and you are on your way.
 
I'm really late to this discussion but I can't stress enough the fact that you are not qualified to do this. The fact that this discussion exists at all makes me nervous. You need a REAL electrician to come hook this up for you. If you attempt to do this on your own the chances are very good that you will damage your dimmers, start a fire, or kill yourself... as in DEAD... Game Over!

It's very possible that your local theater rental house will be happy to rent you what you need to hook your dimmer rack up and come by and hook it all up for you... Nice and safe.

DO NOT ATTEMPT THIS ON YOUR OWN.
 
I have to agree with gafftaper here. HIRE A PROFESSIONAL! I have installed portable racks into disconnects for years (after being taught enough about electricity to do it well), and when I install permenant racks I have a journeyman electrician on staff. Please please please, do not mess with this stuff unless you know EXACTLY what you are doing (and having to ask for advice means that you do not know exactly what you are doing).

Mike

These things are VERY tricky. For example I just recently learned that even at 100% power the sin wave that comes out of SCR dimmers is clipped. You live, you learn, luckily I didn't fry anything in the process.
 
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It looks like a Pass & Seymour 50 amp, 125/250 volt 3 pole 4-wire device; see citywholesaleelectric.com. Grainger has an item like it: part# 4D205
 
I have seen the statement about "the sine wave on a dimmer set to 100% being clipped" twice in recent posts and I am intrigued by this.

I have repaired and adjusted many dimmers of different makes and vintage and I have yet to see a sine wave that is "clipped" on a properly adjusted dimmer. The word "clipped" means that the peak of the positive and negative half cycles has a flat top. Clipping is normally the result of insufficient supply voltage in a circuit or the use of clipping diodes neither of which are normally used in a TRIAC or SCR dimmer. I can see this in a true sine wave dimmer but these are not very common and I have never had the opportunity to repair one so I can't comment.

I routinely adjust dimmers using an oscilloscope which allows me to see the output waveform very clearly - this is much more effective than a true rms meter or worse using a regular DMM and trying guess what the error is due to a non sinusoidal waveform. What you should see on a dimmer output is an error at the zero crossing points i.e at the 0, 180, 360, 720 etc. degree points of the waveform. This distortion is a result of the TRIAc or SCR forward voltage drop and response time. This cannot be described as clipping.

The operation of the dimmer is that as the turn on of the TRIAC or SCRs is delayed by the dimmer setting the sinusoidal output voltage remains at zero and then increases at a rate determined by the rise time of the SCR or TRIAC to the instantaneous voltage corresponding to the phase angle for the dimmer setting. The output then follows the sinusoid curve until it crosses the 180 degree point and the TRIAC/SCR turns off and the output remains at zero until the turn on point is reached. This is definitely not clipping it is called phase controlled dimming.
 
Man, you know, I have never put an oscilliscope on a dimmer so I have no real proof other than the manufacturers (ETC, Strand) and all the installers that I have worked with (Edwin Jones, Texas Scenic, etc) have told me that the waveform coming out of an SCR dimmer is always clipped, even at 100% power. The way I have confirmed this is that when I hook a device that needs "normal" power up to a dimmer (projectors are especially interesting about this and how I learned that this was the case) they will not function even if the dimmer is set to always on.

Mike
 
I think church is correct, the term "clipped" or "clipping" is incorrect. The point is that even at 100% and SCR/SSR dimmer is still switching, causing the waveform chopping that is how SCR/SSR dimmers work. There is a thread somewhere in which I believe STEVETERRY posted oscilloscope images that show this.
 
I think church is correct, the term "clipped" or "clipping" is incorrect. The point is that even at 100% and SCR/SSR dimmer is still switching, causing the waveform chopping that is how SCR/SSR dimmers work. There is a thread somewhere in which I believe STEVETERRY posted oscilloscope images that show this.

Fascinating.

Mike
 
...There is a thread somewhere in which I believe STEVETERRY posted oscilloscope images that show this.
I believe this is the post to which Icewolf is referring. The document attached discusses neutral currents, so isn't quite applicable, but the pictures do illustrate the non-sinusoidal waveform.

"Chopped" is a more definitive term than "clipped."
 
Derek is correct to use the word "chopped" to describe what happens in a TRIAC/SCR dimmer. A good quality dimmer working correctly set at 100% output when fed with a clean supply should produce a sine wave output that has minimal crossover chopping. If you are seeing more than this then you either have an incorrectly adjusted dimmer - for those dimmers where it can be adjusted by pots or the digital control is not performing correcly either because of the design or a firmware error. Do not confuse a distorted sine wave caused by electrical noise on the supply or harmonic components on the neutral with a chopped sine wave caused by the dimmer operation. However this crossover chopping or distortion should be minimal - you have to look for it on the scope. If you are seeing obvious chopping with a dimmer set to 100% then it needs to be investigated.

As the waveform becomes chopped the intensity of the lamps decreases - so if you have significant chopping occuring you will not get the intensity of light from your fixtures.

Just as an aside the ETC, Colortran and Strand dimmers I have worked on all produce good output waveforms as do the old Strand CTM, JTM and STM dimmers designed in the early seventies. Interestingly even the Elation and Behringer products are good.

However having said this the original discussion on this thread was about connecting motors to dimmers. Just because a dimmer provides a good sine wave output does not mean that you should connect anything but a conventional incandescant or halogen lamp to it. If the manufacturer says it is unsuitable for any other type of load then follow the manufacturers guidance. There is more to controlling loads with SCR/TRIACs than the output waveform.
 

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