IEC starters work fine as long as you use them within their ratings. We tend to abuse our equipment here in the US and if you want to do that the IEC device will not take the same abuse as the NEMA device.
Don
Moderator
IEC starters work fine as long as you use them within their ratings. We tend to abuse our equipment here in the US and if you want to do that the IEC device will not take the same abuse as the NEMA device.
Don
Don, Illinois
Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
(All code citations are 2017 unless otherwise noted)
Moderator
I work for Siemens in the US and we make all 3 types of contactors; NEMA, IEC and Definite Purpose. To reiterate what others have been saying, I usually sum it up for people like this:
NEMA starters were/are designed to take the absolute worst thing you can throw at them and survive with a reasonable amount of serviceable life that will likely exceed the equipment that it is controlling. The reasoning behind it was that auto makers would typically change out a complete production line in no more than 4 years, usually around 3 (now it's 5 or sure, but times have changed). That meant that they had to build a completely new line in parallel with the old one prior to the switchover, so to save their capital investment dollars they demanded starters that could be easily re-used without a lot of engineering effort every time. Engineers were expensive, electricians were cheap. That ended up being the NEMA design we love today because you can confidently re-use a NEMA starter for anything else in your plant without getting an engineer involved.
IEC starters were designed during the pre-WWII heydays of European expansion when engineering was a trade rather than a profession. So in Germany and France and England (who joined IEC much later actually), there were people with engineering expertise on every street corner, needing work. In fact, many governments in Europe after WWI had labor laws that essentially mandated that companies employ more people than were really necessary. So to save money on components (especially when most of their raw materials were imported), they used all that available engineering brainpower to decide on the exact amount of contactor necessary for each and every application; no more. They would "rationalize" every installation and process whereby they knew how many operations it was likely to see, how many times per hour or minute, starting current, likely voltage drop, etc. etc. etc. ad nauseum. The end result was that to properly select a contactor, it might take an engineer 1-2 hours on each machine application. If you had a machine with 4 or 5 motors in different uses, that added up to be a lot more engineering time than anyone would ever spend in the US. IEC contactors were also selected based on the expected life of the machine; there was no intent to re-use them somewhere else because you would still have an engineer rationalize it all over again anyway, so the contactor cost was relatively irrelevant. The "throw away" concept crept in in the late 70s only when automated production lines made them too inexpensive to bother fixing, but it should be noted that only the smallest of contactors are considered too cheap to fix. All large IEC contactors have replaceable contacts (at least those from reputable sources). IEC contactors today are still designed with that engineering intensive mentality in mind, although the selection process is a lot more streamlined now.
Definite Purpose contactors are a US concept that somewhat mirrors the IEC mentality, but is reserved for high volume OEM applications and requires even more engineering time because you must investigate and justify every tiny detailed aspect on your own, including short circuit calculations, wear time vs warranty of your end product etc. etc. So if you are designing a machine once and will make it thousands of times without redesigning it, DP made sense because the engineering expense was amortized by volume. DP contactors are terrible choices for one-off applications however because the ratings on the labels are even more application specific than IEC ratings are, so it's really easy to misapply them and end up with damaged equipment or a fire.
Last edited by Jraef; 04-10-07 at 01:15 AM.
Senior Member
I take my hat off Kingpb, excellent post. I was unaware of the diference between IEEE and IEC 60909 for ss calcs in their group.
Call me old-school but I alway was of the opinion that IEC was complete junk. I have pitched hundreds of IEC starters ond Ol's in my day. Part of the reason was probably misapplication, But you cant deny that they are more fragile than NEMA starters and relays. The coils are are fragile too. Even when properly sized you cant beat the old NEMA starters, I have yet to see one melted. Changing out a pair of contacts is easier than a whole starter anyday.
John,
Senior Member
We have used tens, maybe hundreds of thousands of IEC starters and contactors. The failure rate when properly applied is no worse then NEMA starters. We do not use them for plugging applications, but those are pretty uncommon anyway.
Bob
Senior Member
You guys are a gold mine... thanks. Here's specifically what I'm faced w/:
I designed a control panel for a little 3HP process (blender) motor. I've got a few bells and whistles thrown in to meet the owners program - cool. I take the drawing (schematic) to the guy that built their last panel and he starts talking about IEC "stuff" being used in the last panel he built for the same client.
In the commercial world, I always used NEMA equipment if for no other reason than suppliers understood it, whereas IEC was a different language. I saw fellow designers/project managers spending all sorts of effort on getting the IEC parts and pieces right while my NEMA stuff just showed up and worked.
That was a few years ago... I took a break from the electrical world and now I'm back and IEC is all over the place. The project I'm working on needs to be done and the owner already has IEC equipment. In the name of ease of maintenance, I'd like to give them fewer parts/pieces to stock, but not at the expense of safety/reliability.
This particular application sees these small motors running only a couple times a day for +- (60) seconds each time - very infrequent use.
Senior Member
IMHO, no problem here with IEC. Is the mixer a high or low inertia load? Does the mixer start full or empty? If high inertia or fully loaded start, carefully evaluate starting time and possible class 20 overloads; otherwise, just go with it. Are you using fuses or one of those darn MCP thingys for instantaneous protection? Have you ensured your panel can handle available SCC? (concern applies with both NEMA and IEC) We always marked our panels with the maximum SCC the source could have; with just 3HP, you'll probably be fed with long enough #12 which will inherently keep you decently low, but I've been almost adjacent to the main 13,200:480 fed with 4/0 ... a different story.Originally Posted by 831
Senior Member
Apparently, you did not understand that there is NO comparison to IEC short circuit ratings and IEEE short circuit ratings. So, based on that, what IEC short circuit rating of the equipment are you going to use? Have you performed an IEC60909 calculation to determine this? If there is not a dual rating on the "IEC" equipment, which I assume there is not, otherwise you would not be calling it an IEC starter, then you are possibly using a piece of equipment, not properly rated for the application.
IEC KA ratings DO NOT equal IEEE KA ratings...............................
I can not say it any plainer then that.
"Just because you're paranoid, doesn't mean they're not out to get you"
Moderator
True, but you make it sound like it is impossible for an IEC device to have to have two different sets of short circuit ratings.
Square D circuit breakers carry both UL Listed and IEC ratings on their nameplates as do Telemecanique contactors. This way a single device can be applied worldwide.
Just because you can, doesn't mean you should.
Junior Member
We've had significantly more incidents of trouble call repairs related to burned IEC contactors than the NEMA equivilant. All things considered, I've used a rule of thumb of replacing with one size up.
Senior Member
We have not had any significant number of IEC contactors fail, but we mostly use fairly small ones, 30 hp and under, typically. maybe there is more of an issue with larger sizes.
IEC contactors do seem, at least anecdotally, to be more susceptible to failure due to electrical system issues (like short circuits). Stuff that might not kill a NEMA starter may well destroy an IEC starter. I am not sure increasing the size changes anything if that is what damaged it in the first place.
There does seem to be more of an issue with undersizing IEC starters for some reason though. I have seen more than one case where IEC starters were undersized. I can't recall seeing that with a NEMA starter. I suspect someone used the amp rating of the contactor to size it rather than the HP rating. Since most motors, especially smaller ones, are not normally fully loaded, you may well get away with this approach, but it is not advisable.
Bob
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