I keep hearing things about rule changes to UL with regards to panels. I think the number was 508/508A.
What's the big change that has so many companies in an uproar?
Full Version: UL 508/508A?
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Apparently there's been a change to the "traditional" wiring color code.. We just submitted a proposal for an add-on panel to an existing job at a Ford plant, and they rejected it because we followed the old, non-UL508A compliant scheme. I guess you can't use brown for +DC and blue for DC common anymore, it's gotta be blue for +DC and white/blue trace for DC com. That's sure gonna play hell with their electricians, having half the job one way and half the other!
QUOTE(gravitar @ Mar 23 2007, 06:42 PM) [snapback]52004[/snapback]
Apparently there's been a change to the "traditional" wiring color code.. We just submitted a proposal for an add-on panel to an existing job at a Ford plant, and they rejected it because we followed the old, non-UL508A compliant scheme. I guess you can't use brown for +DC and blue for DC common anymore, it's gotta be blue for +DC and white/blue trace for DC com. That's sure gonna play hell with their electricians, having half the job one way and half the other!
Pity the electrician who connects the 24A 24V DC of one panel to the 16A 0V of another just because they are both blue.
I have never heard of brown for plus and blue for common before. Except in AC circuits in the E.U. Where does that come from?
QUOTE(GerryM @ Mar 26 2007, 06:41 AM) [snapback]52088[/snapback]
I have never heard of brown for plus and blue for common before. Except in AC circuits in the E.U. Where does that come from?
I'm not sure where it came from, but it is a pretty common wiring convention. Just look at sensor cables.. With a few rare exceptions (thanks, Bimba!), brown is the DC+ and blue is the DC com. I have seen two common wiring practices, using solid blue for both DC+ and common, and using brown for DC+ and blue for DC com. I've seen spools of white/blue trace wire before, but I never realized this was for UL compliance..
Yeah, you're right, I hadn't thought about prox. switches and stuff.
The NFPA 79 has had the blue and blue/white for a while now, that's all I was thinking about.
The NFPA 79 has had the blue and blue/white for a while now, that's all I was thinking about.
before, it used to be black = 0V , red = +24V, and white or purple = Signal. These were the typical colours in lab applicaions too, but somewhere 10 to 15 years ago, they changed to blue, brown, black....
QUOTE(beegee @ Mar 26 2007, 09:21 AM) [snapback]52097[/snapback]
before, it used to be black = 0V , red = +24V, and white or purple = Signal. These were the typical colours in lab applicaions too, but somewhere 10 to 15 years ago, they changed to blue, brown, black....
It seems to me that as I was learning about electronics as a kid, the color scheme you described was typical, or at least acceptable. In some industries, it probably still is. Don't even joke about hooking stuff up like that in an automotive plant though, or you can expect to be escorted to the door!
All Sensors are blue/brown/black and in European sites (even in Automotive) this is the standard for wiring 24VDC signals...
QUOTE(beegee @ Mar 27 2007, 08:46 AM) [snapback]52142[/snapback]
All Sensors are blue/brown/black and in European sites (even in Automotive) this is the standard for wiring 24VDC signals...
Uhm, not all of them. All the in-cabinet wiring I have done in Sweden has been black (400VAC), red (230VAC), darkblue (24VDC), lightblue (0V in three-phase 400V and 230V), yellow+green (ground), orange (foreign voltage). And it was according to whatever standard is valid in Sweden...
I think this should conclude with: "Standards are so good, everyone should have one of their own!"
The most recent changes to UL508A "Industrial Control Panels" occurred on April 25 2006 with the inclusion of supplement SB - "Short Circuit Current Ratings for Industrial Control Panels".
This requires that specific components in the power circuit are evaluated for their SCCR [sometimes referred to as "let through" or "withstand"] based on the guidelines layed out in the SB Supplement AND that the nameplate includes this data. "Short circuit current:_____kA rms symmetrical, _____V maximum".
Once one gets the hang of it, this is a fairly straightforward procedure. Most major component suppliers [AB, Siemens, Schneider etc. etc.] have updated their product documentation to reflect these changes.
What has got most panel builders and electrical engineers [me included] thoroughly confused are:-
1. There is little or NO information available from where the panel will be installed about what level of SCCR one should design to.
2. The SCCR is different for each manufacturing plant and installation is different. Determining the SCCR is expensive and requires specialized equipment [here come the consultants!!]. Who pays for this, the panel builder or the end user.
3. If the SCCR of the panel is less than that at the installation then the panel must be redesigned. Who pays for this.
4. What is a generally accepted rating one should design to that meets the majority of Industrial installations.
A complete CATCH 22 situation if you ask me.
Still have not got a good feel as to what level of SCCR is really required in the real world.
Is 5 kA OK or should one aim for some higher rating. And if so HOW HIGH. 25kA, 50kA ...........
This requires that specific components in the power circuit are evaluated for their SCCR [sometimes referred to as "let through" or "withstand"] based on the guidelines layed out in the SB Supplement AND that the nameplate includes this data. "Short circuit current:_____kA rms symmetrical, _____V maximum".
Once one gets the hang of it, this is a fairly straightforward procedure. Most major component suppliers [AB, Siemens, Schneider etc. etc.] have updated their product documentation to reflect these changes.
What has got most panel builders and electrical engineers [me included] thoroughly confused are:-
1. There is little or NO information available from where the panel will be installed about what level of SCCR one should design to.
2. The SCCR is different for each manufacturing plant and installation is different. Determining the SCCR is expensive and requires specialized equipment [here come the consultants!!]. Who pays for this, the panel builder or the end user.
3. If the SCCR of the panel is less than that at the installation then the panel must be redesigned. Who pays for this.
4. What is a generally accepted rating one should design to that meets the majority of Industrial installations.
A complete CATCH 22 situation if you ask me.
Still have not got a good feel as to what level of SCCR is really required in the real world.
Is 5 kA OK or should one aim for some higher rating. And if so HOW HIGH. 25kA, 50kA ...........
I understand your frustrations.
I think the whole thing comes from the fact alot of installations in the past gave no consideration to short circuit current. So then in the rare event a ground folt or bolted fault occurs the C.B. or other equipment blows up in someone's face. It goes along with all that arc flash stuff in NFPA 70E.
As far as your specific numbered issues. The end user pays for everything in the end, don't they? You just have to identify the SCCR on the label, or ask the end user what they need and then its up to them to figure out the SCCR. Or, perhaps you could offer the service for an extra fee?
I think the whole thing comes from the fact alot of installations in the past gave no consideration to short circuit current. So then in the rare event a ground folt or bolted fault occurs the C.B. or other equipment blows up in someone's face. It goes along with all that arc flash stuff in NFPA 70E.
As far as your specific numbered issues. The end user pays for everything in the end, don't they? You just have to identify the SCCR on the label, or ask the end user what they need and then its up to them to figure out the SCCR. Or, perhaps you could offer the service for an extra fee?
QUOTE(GerryM @ Apr 4 2007, 12:52 PM) [snapback]52563[/snapback]
I understand your frustrations.
I think the whole thing comes from the fact alot of installations in the past gave no consideration to short circuit current. So then in the rare event a ground folt or bolted fault occurs the C.B. or other equipment blows up in someone's face. It goes along with all that arc flash stuff in NFPA 70E.
As far as your specific numbered issues. The end user pays for everything in the end, don't they? You just have to identify the SCCR on the label, or ask the end user what they need and then its up to them to figure out the SCCR. Or, perhaps you could offer the service for an extra fee?
I think the whole thing comes from the fact alot of installations in the past gave no consideration to short circuit current. So then in the rare event a ground folt or bolted fault occurs the C.B. or other equipment blows up in someone's face. It goes along with all that arc flash stuff in NFPA 70E.
As far as your specific numbered issues. The end user pays for everything in the end, don't they? You just have to identify the SCCR on the label, or ask the end user what they need and then its up to them to figure out the SCCR. Or, perhaps you could offer the service for an extra fee?
Have any of you used the Bussman OSCAR software? It is supposed to step you through the procedure of SCCR rating your panel. My boss went to a seminar last week and he thinks we should buy it
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