15 vs. 20 Amp NEMA Plug on Lightronics AS-42D

I'm stumped. According to the specs on this dimmer, the AC Input cables are "two 20 amp line cords for connection to 2 separate 120 VAC grounded services in any phase combination. Total capacity of the AS-42D is 4800 watts."

The picture of the dimmer shows what appears to be 15A straight pin NEMA 5-15P plugs on the ends of the AC cables as opposed to NEMA 5-20P straight pin plug (with one pin offset 90 degrees). How are the dimmers rated for 4800W when using 5-15P NEMA plugs?
 
Yup, sure looks like two NEMA 5-15P plugs to me.

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Portable Dimming - AS42 Series

The key may lie in the "-UB" and "-UT" suffixes. I can think of no other manufacturer that offers "UL-508 Compliant" as an option.
 
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The fine print on most of these types of dimmers is that the CORD is rated for 20A, but the plugs are not. If you need to use the full 4800W, then you must replace the plugs with proper 20A plugs. I don't know about these in particular, but I've seen this in other instruction manuals for similar units.

-Fred
 
each of the four dimmers is only rated for 1.2Kw, see under AS-42 in the photo. thats 10a, thus a 15a outlet is fine and in fact a 20a outlet would be incorrect.
 
Actually, each dimmer is only a 1.2k, but there are 4 dimmers and only 2 power supplies. Each plug supplies the power to 2 of these 1.2k dimmers, thus 20A (at 120v). Fredthe is right here, it's most likely the dimmers and cables are rated for 20A, but you would have to add 5-20P plugs to them to actually use them to there full capacity. I think that I brought this up in a post a while back, and I will say it again. I think that this is an extremely dangerous practice that most, if not all, of the shoebox dimmer manufacturers participate in. Many (most?) users of this type of product will see the 1.2k/dimmer and do it without even realizing that the connector is not rated for the load. I don't even understand why they do it. To save the couple dollars that they would have to spend to get 5-20P? Or, I guess it might be because the 5-15P fits in both the 5-15R and 5-20R while you can't plug a 5-20P into a 5-15R and 20A circuits can be rare in the kind of venues these dimmers are marketed for.

-Tim
 
its not a hazard. the guts (and current carrying capacity) of a 5-15 are exactly the same as a 5-20. The only difference is the blade turned sideways. 5-15 receptacles are legal (as long as its one duplex or more, cant have a single 15a receptacle on a 20a circuit) on a 20 amp circuit. 5-20 receptacles are less common. The only problem is UL wise, anything drawing over 15 amps needs a 5-20 plug, so there is grey area to the legality of it, but safety wise its fine. Its important the user make sure they arent overloading the circuit these are plugged into, but that is important regardless of the plug.
 
I understand that, but it is still dangerous because you can plug it into a 15A circuit when it has a 5-15P. While I know that one should be sure that you are in fact using a 20A circuit, a lot of people (and the percentage of people that fall into this category is far greater with this type of dimmer than say Sensors) don't know to check this and just assume that just because they can plug it in, it's right.

It's just my opinion.

-Tim
 
I understand that, but it is still dangerous because you can plug it into a 15A circuit when it has a 5-15P. While I know that one should be sure that you are in fact using a 20A circuit, a lot of people (and the percentage of people that fall into this category is far greater with this type of dimmer than say Sensors) don't know to check this and just assume that just because they can plug it in, it's right.

It's just my opinion.

-Tim

I see your point, but even with the 5-20 plug, and 5-20 receptacles, someone could plug both power cords from the dimmer into the same receptacle and still overload the circuit. Same goes with 5-15 receptacles on a 15a circuit and smaller dimmers.

This has always been a tough dillema, from dimmer packs to 2K fresnels used by the movie guys.....
 
Dangerous is probably not the correct word. Load a 15 amp circuit with 20 amps and the breaker trips.
 
Dangerous is probably not the correct word. Load a 15 amp circuit with 20 amps and the breaker trips.
Unless it doesn't, at least not until the 14g. wire heats up enough to start a fire. Or it holds during set-up and focus but blows during the show: http://www.controlbooth.com/forums/what-went-wrong/11954-electrical-fire.html . Or some well-intentioned but misguided person keeps resetting it: http://www.controlbooth.com/forums/everything-else/10433-why-ocpds-matter.html .
 
Strangely enough I have seen this pass field inspection here in Ontario many times especially on distros because they are not supposed to be used by the general public but are only intended to be used by people who are trained in their use i.e. know how to calculate the load and stay within the limits. This is why this type of equipment will normally be found with a label that says, Äuthorised users Only". The logic on the outlet is that 15 A and 20 A outlets have exactly the same amount of contact area and insulation so if anything the 15A outlet is significantly over designed.

You can also argue that there is more risk from someone using an extension cable that is undersized after all there is nothing that stops you using a 18AWG cable for a 15A load or even a 20A load. After all no one says that you should only be able to buy 14AWG cord.

We sometimes forget that this is considered professional equipment and it is not intended to be used by people who are untrained. Ever noticed that many of the manufacturers labels carry the notice "not for residential use".

As for the breakers the normal failure mode is it trips early but there is another breaker or fuse further up the line which in a worst case scenario will also trip. However one of the the biggest problems with all of this is I have seen electricians choose breakers and fuses in facilities without realising there is a need to do a Fuse/breaker Time Current Coordination analysis so they can create some scary problems where the higher current breaker can actually trip before a lower current breaker. This happens even though electricians are not allowed to select breaker and fuse sizes and types in anything other than a house. Get this wrong and a short circuit on a single branch can shut down an entire building.
 
I understand that, but it is still dangerous because you can plug it into a 15A circuit when it has a 5-15P. While I know that one should be sure that you are in fact using a 20A circuit, a lot of people (and the percentage of people that fall into this category is far greater with this type of dimmer than say Sensors) don't know to check this and just assume that just because they can plug it in, it's right.

It's just my opinion.

-Tim

This is standard practice on all 1.2k portable packs I've seen and there is nothing unusual about it. I would pretty much say that it's made the way it is so it's flexible, if your not using more then 15amps you can plug it in. If you are you can still plug it in but you would have to make sure the outlet and circuit can handle it (that it has the extra slit in it). It is a greay area but not unusuall however there are alot of people that have no clue about the different outlet and plug for 15 vs. 20amps. But then again you can look at it from another point of view, most standard consumer extension cords aren't even rated for 15amps, but you can still plug it in. It's up to the user to follow the guidelines as there's nothing stoping that extension cord of going up in flames if you put 15amps on it.
 
I understand that, but it is still dangerous because you can plug it into a 15A circuit when it has a 5-15P. While I know that one should be sure that you are in fact using a 20A circuit, a lot of people (and the percentage of people that fall into this category is far greater with this type of dimmer than say Sensors) don't know to check this and just assume that just because they can plug it in, it's right.

It's just my opinion.

-Tim

That's what overcurrent protection is for! You might hate the blackout, but you won't be burning down the building!

ST
 
:neutral:
So the NEMA 5-20P is obsolete. We don't need it. It serves no purpose...

No!!!! It just doesn't apply in this case as the dimmer pack can be run at 20 amps or anywhere in between. It's not like pluging in an apliance that would pretty much always draw the same current. Dimmer packs would vary depending on the load. It makes no sense to put the 5-20P on it. Just like I stated with most extension cords aren't rated for 15Amp but they can obviously be plugged into a 15amp circuit and are UL approved. On a normal 20amp appliance, yes the 5-20P should be used, but there is an exception as this unit can be setup several different ways as far as loads.
 
Thinking that industrial places this dimmer was designed for are already in a traditional scale of compliance at 20A/12ga wire to outlets. That's a industry thing that 15A wiring for industrial use is not sufficient since way back. Others more versed in the code would be able to better able to agree on this even if not find what I remember for the exception of 15A plugs used for 20A power in stage and studio type use.

In other words, where this dimmer is designed to plug into, it is by code assumed that all wiring and overcurrent protection is already rated for it. The use of a 5-15 plug while I also disagree with its use, is however common. Once did some not within code 5-20P to L21-30R adaptors for a show. They were to plug directly into the back of a AC-Distro rack which didn't have such an output - later upgraded and we don't use such things.

Still the adaptor got to the job site and even though the rack had 20A outlets on it and such plugs will have plugged directly into it, some stage hand wasted upteen amount of hours in removing all my commercial grade 5-20 plugs and replacing them with store bought home owner grade 5-15P plugs. Me in being "proper" sent out a plug type no local stage hand was familiar with or took the time in a rush to get the show out and re-wire all the plugs so as to familiarize themselves with it or its connection direct to the AC rack.

Dangerous adaptor to do but breakered at 20A and while if un-plugged and touching a prong one could get shocked, still necessary for the production to do this before I added such an outlet to the rack. Still though it was a question of me doing a proper 5-15P plug, and them pro's with at least ten years in the industry using it not having seen it before thus swapping it out. The 5-20 I use where I can but simply enough ain't trained into the end user sufficiently.

Years ago I also switched all our cable from 14/3 to 12/3 for much the same reason - too many professionals on a jobsite not calculating the load even for an edison cable by way of cable length and draw. Playing with fire those "expert or professional" that would use say a 100' run of say 16/3 to overload with 20A. Nothing will help them even idiot proofing - provide the 5-20P, it will confuse and cause them to remove it. Normal Edison if commercial grade is fine.
 
@ ship

at least they replaced the connectors. I have seen guys take linesman pliers to a 5-20P and turn the sideways blade straight again.
 

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