| Electrical semantics [message #59554] |
Fri, 09 October 2009 17:48  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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When I do advance work for rock shows and corporate business shows I have to advance the power. For our portable distros I need 120/208 3ph (3 hots, N and G) from say 100A-400A depending on the show and I refer to this as a 5 wire system. If someone were to say they had a 4 wire system I would think that would be 3 hots and a ground with no neutral for running 3 ph motors etc. with no 120V component. The only other thing it could be is single phase with 2 hots, N and G to call it 4 wire. One theater I am talking to is specing the 3 hots, N and G as a 4 wire system apparently not counting the ground. I say this should be called a 5 wire system as 5 wire feeder cable is used and I have always called it 5 wire. Am I correct?
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Electrical semantics [message #59562 is a reply to message #59554] |
Fri, 09 October 2009 18:44  |
tmaki
Messages: 200
Registered: September 2005
Karma: 0
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Senior Member |
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John R. Lebetski wrote:
>
> When I do advance work for rock shows and corporate business shows I have to advance the power.
> For our portable distros I need 120/208 3ph (3 hots, N and G) from say 100A-400A
> depending on the show and I refer to this as a 5 wire system. If someone were to say they had a
> 4 wire system I would think that would be 3 hots and a ground with no neutral
> The only other thing it could be is single phase with 2 hots, N and G to call it 4 wire.
Kind of like the GMC... :-)
> One theater I am talking to is specing the 3 hots, N and G as a 4 wire system apparently
> not counting the ground. I say this should be called a 5 wire system as 5 wire feeder cable
> is used and I have always called it 5 wire. Am I correct?
I'd say so. Depending on who sent you the spec, they might
just assume that you assume G. If you're going in with
Cam-Locs, ask them how many females and what colors. If you
have to clamp onto the bars, there's no telling. Or just ask
to talk to the house electrician, but you already know that.
It always amazes me how much front office people don't know
about their theatres. Spec sheets are often way out of date.
It's always such a luxury to personally check it out. Not
too easy if it's way out of town. If I can't see it or be
assured of a spec, I just load the truck heavier to cover
the unexpected.
Good luck.
Toby Maki
'73 Glacier 230
Riverside, CA
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| Re: Electrical semantics [message #59569 is a reply to message #59554] |
Fri, 09 October 2009 19:50 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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I'd agree with you. 5-wire, but many older places, and those who don't care much about safety, use Ground as a Neutral...
some folks use a transformer to step down 208 to 120 and tie one leg of the load to Gnd. this will give you an effective 120 with a neutral, but the neutral load is through the transformer to the hot legs, which leaves the gnd as a gnd. Your transformer load side is now effectively the source panel.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Electrical semantics [message #59610 is a reply to message #59554] |
Sat, 10 October 2009 08:43 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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JohnL455 on Fri, 09 October 2009 18:48 not quoted.
John,
As another that gets into situations that are strange, allow me to first commiserate and then offer some possible assistance. Common parlance (note allow for regional variation) now assumes (you remember what we say about that) that a machine or safety ground is included.
Our coaches are what is now called 3-wire 240. The neutral splits the 240 into 2 -120s. The safety ground is not mentioned. The new cable I just got to make a coach extension cable is labeled as 3-conductor, but it contains 4 wires. It is 3ea - 6AWG conductors and an 8AWG ground.
What is usually referred to as 240-3 Phase is 3-phase as delta and the neutral is splitting one leg, so hot to neural is 120-167-120. This is what is usually in 240v machine shops. Interesting is that lights are manufactured for the 167 leg.
What is often called just 208 or 120/208 is 3-phase "Y" with 120 to neutral on each of three legs, this is often used in stores and theaters where they don't need much 3-phase but need a lot of 120 and need to keep the 3 phases of the supplied power balanced. It is 208 hot to hot and can run most 240v 3ph motors.
The confusion saver is the NEMA (National Electrical Manufactures Association) has established a convention that made all the local nomenclature disappear. All connectors are simply described.
A grounding wall plug or outlet is 5-15 (5 indicates 120v service, 15 is the design current) followed by a P or S for Plug or Socket.
The coach (GMC) plug is a 14-50 (14 means it is 240v 3wire (see above) and capable of 50 amps. So, 14-50 (p or s) is all you need to know to get a correct connector.
There is the L version - too. These are called locking plugs or twist locks as opposed to straight bladed connectors with a locking ring. L5-30S is the socket on most 3Kw portable generators. If you want to connect to that you get a cable with a L5-30P on the end (very common in marinas).
There are tables of these - with lots of pictures - on the web. I got a big one from Hubbell years ago and it is on my shop wall. I only remember the ones I use regularly.
The common connector referred to as a cam-lock is used on single wire heavy cables - like for welding. Where the connectors push together and get locked with a fractional turn. These are not yet a NEMA standard, but the most common is called a Cam-Lok based on the Crouse-Hinds (now Cooper) and....
Yes, this would make any 3ph a 5-wire connection. After all, each 1/2~3/4 in wire is connected separately.
Then there is theater. . .
If by cam lock, you really where meaning twist-lock (a single connector with arched pins that locks together). They use lots of these. There used to be many manufacturer specific connectors, but with the advent of the NEMA standard most of them have disappeared (Thank God). They also use several other connectors that are common to theater only and though they may be UL type accepted, they are not a NEMA standard part - Good Luck with those. Fortunately they are rarely seen these days as primary power outlets.
Well, I'm tired of writing about about this, so unless someone has a question, I'll sit down and work on my coffee.
Matt
Disclaimer for non-USA readers:
I do not know if all this applies in Canada. I'm sure it does not apply across any ocean.
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Electrical semantics [message #59614 is a reply to message #59610] |
Sat, 10 October 2009 10:47 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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120/240 volt 60 cycle is pretty much a Western Hemisphere phenomenon with a few exceptions like Taiwan, Philippines, Korea, and parts of Japan, as some of the Pacific islands. Even within the Western Hemisphere there are some differences like 50 cycle in Chile and 127 volts service in Mexico.
Within the above areas not all of the distribution and plugs are not the same. I have never run into any differences in Canada but there I was primarily a user / equipment provider and not an installer / power provider.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Electrical semantics [message #59657 is a reply to message #59554] |
Sat, 10 October 2009 18:42 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Matt thanks for all the detail, which is great reinforcement. I just want to know if I should call 120/208 3PH w ground a '5 wire system' since there are 5 wires. We use 5 E series Cams on the distros and they have L21-30, L14-30 L5-30 and 5-20 recepts on them. Feeder is from 0000 down to thinner 2ga depending on the size of the distro.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Electrical semantics [message #59701 is a reply to message #59657] |
Sat, 10 October 2009 22:48 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| JohnL455 wrote on Sat, 10 October 2009 19:42 |
Matt thanks for all the detail, which is great reinforcement. I just want to know if I should call 120/208 3PH w ground a '5 wire system' since there are 5 wires. We use 5 E series Cams on the distros and they have L21-30, L14-30 L5-30 and 5-20 recepts on them. Feeder is from 0000 down to thinner 2ga depending on the size of the distro.
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Man,
I'm glad I'm not buying the copper for that.
They are camlocks - Huh? Well, that is pretty much the only disconnect for 4/0.
I guess you could call it 5-wire 120, because the other 5-wire is not all 120 to neutral.
That's what 21 is? I've seen an L21-xx, but I don't even remember where or when. Pretty distinctive with the pin in the center.
As 15-xx is a 4-wire for 240v3ph and there does not seem to be a NEMA designation for the 240V delta version, I guess it is pretty safe to call the type 21 a 5-wire.
That's my slant.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Electrical semantics [message #59769 is a reply to message #59554] |
Sun, 11 October 2009 15:06 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Yes the L21 has all 3 legs and N and G with the G on the center round (slightly longer to mate first) and N on the keyed prong where G would typically be. When installing you have to cut the green slightly shorter as that cavity is higher up on the connector body and make sure, as always, you are putting the connector on the correct end of the wire so the handedness is correct and you don't have to cross conductors or it's a real mess.
John Lebetski
Woodstock, IL
77 Eleganza II
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