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Old 09-12-2007, 05:45 AM   #16
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magnetic starters for compressors


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Originally Posted by Norcal View Post
IEC controls are just more to fill our landfills, throwaway junk. NEMA is a lot easier to specify, all you need is to know the voltage, HP, # of phases. BTW most NEMA starters come w/ adjustable O/L relays with the exception of Cutler-Hammer "Freedom Series" starters and their "heater packs". Siemens/Furnas ESP 100 and SQ D Motor Logic are a couple of examples.

Good results are useally not possible when somebody tries to put 10 Lbs. of manure in a 5 lb. bag.
In case you don't know Norcal, the rest of the world uses IEC switch/controlgear. Also, the rest of the world is metricised, something that the US must (sooner or later) change to.

I'd never heard of or seen a 'magnetic switch' until I joined this forum.

As far as magnetic switches being easier to specify, if you can't convert old fashioned horsepower to modern Watts, you shouldn't be playing with these devices. The effort involved in doing this simple conversion is three fifths of five eigths of bugger all.

EDIT:
Thermal overload relays that can be connected to contactors are generally adjusted to 125% of the FLA (running current) of the motor.

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Old 09-12-2007, 08:59 AM   #17
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I am quite aware of most of the world being metric, the only things I love about IEC devices is that they mount on DIN rail and the adjustable O/L relays, other than that they are a waste of natural resources, miniaturizing components means trade offs, you do not get more reliablity w/ smaller packaging, do I use them? yes they have their place but a NEMA device is superior to IEC in quality and reliablity.


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Old 09-12-2007, 11:39 AM   #18
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Norcal,
Back in the old days electricians loathed IEC. Some still do. They pointed to the contact. Tiny contact compared to large NEMA contact for currrent sake. I was one of them.
But then some IEC manufacturers decided that they would design their contactors/starters that can be rebuilt.
I don't throw out IEC contactors anymore. I save the bad ones and refurbish them in my spare time.
You can get replacement coils and contact sets just as easy as the NEMA.
Try this web site. www.wegelectric.com. Go to their "E-Catalog" and take a look at what is available.

Why would I spend over $1500 for a NEMA 5 starter when I can get one for $500.

Of course if you prefer the NEMA then no one will change your mind. But to say that IEC is inferior would not be a true statement.

Benshaw makes a # 5 NEMA starter with adjustable OLR for around $750. No more Square D for me. To expensive.

Take a look at duty cycle also. I have seen some IEC with 1 million electrical cycles at 3 million mechanical cycles. Now thats pretty darn good.

Last edited by J. V.; 09-12-2007 at 11:45 AM.
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Old 09-12-2007, 01:44 PM   #19
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Why would the rest of the world think we have to go metric? We already are in many areas, just look at the auto- industry gotta have a mechanics set of US standards and a mechanics set of metric. What a Joy!!! Our science community is metric, has been for years and years. Me for one.... you can keep the metric system out of our electricial industry. And don't forget the good ole USA has done pretty freakin well for itself without the intrusion of the metric system into every aspect of our lives. When I get gas in my truck I happen to like paying for gallons and you can put those liters where the sun doesn't shine. And hey next time we have a world tragedy (like an earthquake) lets keep our out of date American dollars at home. You see I have an opinion about the metric system. 35 years ago I heard the same statement "the USA is going to have to go to the metric system sooner or later" and we still haven't. The only people that push the metric system are politicians or people who have been sucked in by the metric syndrome. I like the American standard unit, it has served me just fine and I refuse to conform to other peoples arrogance about how much better things are with the metric system. Every time I have to go out to my truck to get one freakin metric tool to get a panel apart I think of the metric system and politicians and the French ( the exception being Jacques Cousteau... wasn't he really American? )

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Old 09-14-2007, 11:47 AM   #20
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Hi, can someone tell me the purpose for a magnetic switch or starter for a compressor? Doe's it help in reducing wear on the motor? is it really needed? I plan on getting a 220v 1 ph. 2 stage and want it to last longer then me. Thanks Jim
I'm not sure if anybody answered your question.....the answer is that magnetic starters are controllers designed to provide motor overload protection.

These starters are installed in addition to the controllers on the compressor. However, there is a reason that all manufacturers instruct buyers of their products to use licensed/certified electricians to install the electrical power, it can kill in a heartbeat.
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Old 09-14-2007, 12:39 PM   #21
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Originally Posted by buffalonymann View Post
I'm not sure if anybody answered your question.....the answer is that magnetic starters are controllers designed to provide motor overload protection.

These starters are installed in addition to the controllers on the compressor. However, there is a reason that all manufacturers instruct buyers of their products to use licensed/certified electricians to install the electrical power, it can kill in a heartbeat.
Actually Buffalonyman, you have addressed the real issue here, which I (for one) have failed to do.

But further to your post, I believe that the OP asked about '2 stage' starting. In this case, I believe that he is talking about star/delta starting. Generally this method is only used for:

a] high starting current loads (large motors).
b] loads that require less mechanical shock at starting.

In the case of 2 stage starting, an IEC star/delta arrangement is recommended, which automatically incorporates an adjustable thermal overload. The overload must be set at 125% of the FLA (running current) of the motor.
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Old 09-14-2007, 12:47 PM   #22
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Actually Buffalonyman, you have addressed the real issue here, which I (for one) have failed to do.

But further to your post, I believe that the OP asked about '2 stage' starting. In this case, I believe that he is talking about star/delta starting. Generally this method is only used for:

a] high starting current loads (large motors).
b] loads that require less mechanical shock at starting.

In the case of 2 stage starting, an IEC star/delta arrangement is recommended, which automatically incorporates an adjustable thermal overload. The overload must be set at 125% of the FLA (running current) of the motor.
He did mention its for sale at lowes, and is 220v 1ph. star/delta is a 3-phase connection. Further, these connections are made in the motors.

2 stage compressor is explained here... http://www.popularmechanics.com/home...31.html?page=2
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Old 09-14-2007, 01:47 PM   #23
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He did mention its for sale at lowes, and is 220v 1ph. star/delta is a 3-phase connection. Further, these connections are made in the motors.
Actually, if the motor is three phase, the connection can be made externally.
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Old 09-14-2007, 11:32 PM   #24
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All the compressors I have seen at big box stores such as Lowes, Home Depot,and others are single phase, I won't say they do not sell 3 compressors but would be quite rare.
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Old 09-14-2007, 11:53 PM   #25
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Also most light duty air compressor useally are less than 5 hp and they have pretty werid rating vs of real motors rating is

most air compressors are rated by CFM @ 90 or 125 or 175 PSIG depending on the manufacter and type it used

very rare to see a true 3 motors used in the resdental useage unless they have 3 supply on hand or RPC [ rotary phase convter ]

merci , marc
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Old 09-15-2007, 09:45 AM   #26
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Actually, if the motor is three phase, the connection can be made externally.

I didn't mean to imply they cannot, it is possible to purchase a 3-ph motor with the leads unconnected. I've connceted 3, 6, and 12 lead motors

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