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SDL
04-16-2009, 09:10 AM
In the US what is the relationship between UL lised products and Nema, Is UL an assurance that Nema has been followed or are they two unrelated seperate codes?

Steve Larner

oldtiffie
04-16-2009, 09:26 AM
Steve,

UL (Underwriters laboratories) seems to be to do with safety etc. and things relating to risk and insurance.

http://www.ul.com/global/eng/pages/

http://www.google.com.au/search?hl=en&q=UL&btnG=Google+Search&meta=&aq=f&oq=

Where-as NEMA is a US site for standards for things electical etc.
http://www.nema.org/

http://www.google.com.au/search?hl=en&q=NEMA&btnG=Search&meta=

Do you mean NIST (US National Institute of Standards and Technology) for engineering and other standards and certification etc.
http://www.nist.gov/index.html

http://www.google.com.au/search?hl=en&q=NIST&btnG=Search&meta=

The NIST equivalent in Australia is NATA - the National Association of Testing Authorities.

http://www.nata.asn.au/

http://www.google.com.au/search?hl=en&q=NATA&btnG=Search&meta=

J Tiers
04-16-2009, 09:37 AM
UL is as mentioned a safety organization. They are an NRTL per the IEC. Other NRTLs include ETL, and CSA. (NRTL=Nationally Recognized Testing Laboratory)

They write regulations, and test to them. Well, any more, they more or less rubber-stamp the european regulations, but........

If a piece of equipment is UL recognized, or tested to UL standards by a different NRTL, that satisfies the OSHA requirement for an item to be tested for safety.

NEMA is a separate industry organization. They also write standards, but they are somewhat "internal". There is no directly associated "NRTL".

NEMA standards may be written into OSHA, UL, FM, etc regulations, and are then enforceable.

wierdscience
04-16-2009, 09:50 AM
UL is also not a part of the US government,they are a private organization that represents insurance underwriters among other customers.Product testing is they're forte.

They are so good at what they do the Chinese counterfeiters usually include the UL label on they're product even though it may burst into flames on first use:)

SDL
04-16-2009, 04:31 PM
UL is as mentioned a safety organization. They are an NRTL per the IEC. Other NRTLs include ETL, and CSA. (NRTL=Nationally Recognized Testing Laboratory)

If a piece of equipment is UL recognized, or tested to UL standards by a different NRTL, that satisfies the OSHA requirement for an item to be tested for safety.

NEMA is a separate industry organization. They also write standards, but they are somewhat "internal". There is no directly associated "NRTL".

NEMA standards may be written into OSHA, UL, FM, etc regulations, and are then enforceable.

OK I understand how UL has its sets of rules we design Control Panels to UL 508 that are UL listed and we have the random 4 inspections per year, but you see specs that require compliance with UL, typically UL 508 but also require Nema rated components and we have never looked at NEMA other than cabinet protection ratings, how do the two fit together.


Typically if a customer specifies UL 508 does that mean they have to accept an ETL marking to the 508 specification? I have known customers in Canada not accept the UL as its not ULc and insist on a CSA inspection.

Steve Larner

J Tiers
04-16-2009, 08:31 PM
As I understand it, if any NRTL tests to a standard, and passes the product, it is agreed that it passes.

Wierd's comment is a case in point..... Although there are counterfeit UL products such as he mentions, there are also products inspected to UL in china by the chinese version of UL. UL accepts the chinese tests to UL as valid and a number is issued. (the validity of those tests is, IMO from some inside knowledge, open to question in some cases)

We had our products tested to the CE requirements by a US NRTL, at the same time as the UL tests were performed. That is accepted as proof of compliance, in the absence of evidence to the contrary.

And, OSHA as I understand it also accepts any NRTL testing to the UL standards.

The distinction may arise if the testing was done to a standard DIFFERENT from the national standard. For instance, testing to UL only may not satisfy CSA. In that case, the product may be required to be tested to the relevant national standard.

But any NRTL should be able to do it without a question.

As for NEMA, there is an interconnection, in that NEMA standards are written into other regulations. But that does not preclude an IEC contactor, for instance, which is NOT NEMA/UL at its nominal rating, being used, so long as it is derated to a suitable NEMA rating. That may involve a 40A IEC contactor being used in a 20A NEMA/UL application, for instance. Most companies give a UL rating and the myriads of specialty IEC ratings, both.

The NEMA ratings take into account things like being able to interrupt locked rotor current of an X HP motor, where IEC simply gives a current rating for some application, and leaves it up to you to determine suitability. You can put the NEMA part into any X HP situation without worrying, while the much lighter-built IEC part will need some "design".

rdfeil
04-17-2009, 01:04 AM
The above information is correct, but just for clarification...
NEMA and UL are exclusive of each other. A product can be NEMA rated and not UL listed (rated) or a product can be UL listen and not NEMA.

UL is a safety rating organization ONLY. They test products for safety issues related to their use and application.

NEMA (National Electrical Manufacturers Association) is primarily a mechanical/electrical durability rating, in this context.

Generally a NEMA rated device will be heaver duty at a given rating than an IEC or CSA rated device. Please don't get me wrong, IEC and CSA are also good rating agency's.

If a device is used within its published ratings (NEMA, IEC, CSA etc.)it will meet UL safety ratings (it may need to be tested to prove it but it will pass).

As far as a customer requiring a UL-508 certification, they are the customer and if they are willing to pay for it they get what they want. I build custom control panels and use ETL as the certification, the cost is less than 20% of UL and is accepted within the USA the same as UL by all state and federal inspectors. I had one job that the engineer specified UL-508 and I asked if ETL was acceptable. The engineer said NO! I asked why and he said he had never heard of it and the inspectors would not accept anything but UL-508. After I told the customer what UL would add to the job (+-10K :eek: ) they asked if there was any way to appease the engineer. I said I would try.... After presenting the engineer with a letter from the Washington State Labor and Industries inspector general stating that ETL was accepted the same as UL-508 the engineer apologized and said thanks for the heads up :D .

I hope this helps a little.
Robin

lazlo
04-17-2009, 10:58 AM
Generally a NEMA rated device will be heaver duty at a given rating than an IEC or CSA rated device.

Wow, I'm surprised the European crowd, especially John, didn't blow a gasket over that comment :D

SDL
04-17-2009, 11:36 AM
Wow, I'm surprised the European crowd, especially John, didn't blow a gasket over that comment :D

No problem if we want a 5kW motor we fit one that will do 5kW of work you fit one that will do for 7kW (with a badge saying 5kW) and then say how good it is that you can push it up to 7kW:D

Steve Larner

PS Hows April on the calender?

rdfeil
04-18-2009, 01:15 AM
Lazlo,
I really meant no disrespect for other rating agencies ;) , but I think Steve really got it right. We, in the USA have NEMA ratings, which really means that we pay more for a product to do a certain job, while the product could actually be half the size and cost :D . Look at out electric motors. Some have a service factor as high as 1.25 which means that a 10 HP motor can easily do 12.5 HP of work all day long as long as it is kept within its temperature ratings. Once in an emergency I installed (temporarily) a NEMA 4 (100 HP @ 480 volt 3 phase) contactor to run a 250 HP motor. Worked fine for a week and when I finally got the right replacement and was able to open up the undersized one, to look at how much damage I did, I could not see any!
I also work on a lot of equipment imported from Europe, Holland and Italy specifically. The electric control components are ALL IEC rated and applied properly by their ratings. I have not noticed any higher failure rate in this equipment than good old USA equipment, both are on par with each other. So with that said, If I offended any of out European or Canadian members I am very sorry :o as that was not in any way my intension.

Lazlo, thanks for pointing out that my comment could be taken in a bad way. I will try to be more diligent in explaining myself in the future.
BAD BAD Robin......

Sorry to some and Thanks to all,
Robin

J Tiers
04-18-2009, 01:37 AM
Actually, the IEC ratings ARE different, and an IEC contactor to fit a particular application won't be half the size and cost, unless you accept possible damage from forseeable overloading.

NEMA ratings are made so that you just match up the ratings of the contactors and motors, no sweat.

And there is no law that says a motor MUST be made to an SF of 1.15...... there are plenty of SF 1.0, and even duty-cycle rated motors. It's all in what you want.

The IEC ratings tend to be very specific, and IEC contactors tend to be "definite purpose", meaning essentially that they are made for operation between certain limits, which are design specific. "That" 5kw motor and "this" contactor. A different 5kW motor might require a different contactor.

I was specifying some Cutler-Hammer contactors, from their IEC series, and found there are at least 25 ratings categories.... You pick what you are doing, and that gives you the category. then you find the size which gives the rating you need in that category...... I don't have the listing in front of me, but there were several categories for lighting, and one for connecting capacitor banks, among others. It can be very confusing.

The NEMA parts are more "general application". Pretty much any 5 HP motor and any contactor rated for 5 HP at the voltage of interest can be used together and no problems result.

It's a different philosophy of ratings and a different approach to design. Europeans often tend to try to use minimal materials, accepting lower life, or possible problems later.

That's one reason for the big fuss over power line harmonics in the EC. The neutral wires in europe were often undersized, counting on balance between phases to minimize the neutral current resulting from single phase loads. So they cannot take the higher currents caused by harmonics (harmonics don't balance like 50Hz power current).

lazlo
04-18-2009, 01:38 AM
thanks for pointing out that my comment could be taken in a bad way.

I was just teasing Robin -- John makes his living repairing IEC motors, so I was surprised he didn't take the bait :D

IEC motors are pretty rare in the 'States. I've only seen one, and it was on MickeyD's Hurco, and he transplanted it to a Lagun he was selling.

rdfeil
04-18-2009, 01:59 AM
Lazlo,

I figured you were teasing, but the point is very real. I could have easily offended someone and that wasn't the intent. If I wanted to offend I would have started talking about LUCAS electrical..........................

Go ahead flame on :D

Robin

RancherBill
04-18-2009, 05:50 PM
My take on NEMA is that it relates to the physical characteristics of the product only.

The physical in terms of interoperability between all the manufacturers. Nema specs things like motor mounts, screw sizes spacing etc. It also specs intended usage. For example, for regular use or 'explosion proof' usage.

Thus you can design a project, define your specs and find products that meet your physical requirements (size, heat,blah blah blah). It should all fit together without having to worry about the mechanical or usage characteristics.

You then build it and then send it to UL to see if your design is safe for it's intended usage.

J Tiers
04-19-2009, 12:13 AM
This may be helpful in understanding the differences in NEMA and IEC:

http://ecmweb.com/mag/electric_differentiating_nema_iecstyle/

The point is made that the two differ considerably

IEC starter and contactors tend to be:

Special purpose
smaller
cheaper
disposable, not repairable
require "design work" to apply correctly to each specific application, even including motor duty cycle, etc.

NEMA starters and contactors tend to be

General purpose
more substantial
more expensive
repairable, not disposable
can be applied simply without in-depth knowlege of the specific and limited application