UL Rating vs NEMA Rating for Motors 1

[Eng8492]

We are designing a piece of equipment that will have a UL nameplate rating of 24O VAC because this is standard voltage at all of our customers. However, the equipment will contain a motor with a 230VAC on its nameplate because we cannot find a UL-recognized motor at 240VAC.

Past experience shows that UL will not accept UL-Recognized components if they are operated at higher than their nameplate spec with expensive additional testing. So UL will not accept a 230 VAC transformer in a device with a nameplate that says 240 VAC without expensive testing.

Is there some special rule that allows 230VAC motors to be accepted by UL when operated at 240 VAC without expensive testing?

Note- this question has nothing to do with whether a 230VAC motor will operate with 240VAC. Rather its about nameplate ratings and safety agencies.

 

[magoo2]

Motors are typically rated with a nameplate voltage a bit lower than the rated service voltage. However, motors are suitable for operation with a 10% tolerance based on their nameplate voltage.

You can look at ANSI C84.1 which shows the typical service voltages used in North America.

NEMA MG-1 gives you the 10% voltage tolerance for motors.

So, in brief, a 230 volt motor will provide successful operation over the range from 207 to 253 volts.

The UL folks are well aware of this standard practice.

 

[jraef]

There are two different voltage classifications: Distribution (or Service) Voltage and Utilization Voltage. Equipment used for distribution and control must be rated for the Distribution/Service Voltage, end-use equipment, such as motors, is rated at the Utilization Voltage. So 240V is the Distribution Voltage, 230V is the Utilization Voltage. 480V is Distribution, 460V is Utilization. 120V = Distribution, 115V = Utilization, ad nauseum.

The problem is, you are apparently looking at using a UL Recognized (UR) motor, which is only intended to be used as a component in a tested and listed combination with something else. If you bought a UL Listed motor, nobody would care, the motor has ALREADY been tested and listed by UL. So assuming you are going to get the complete assembly UL listed as a whole, regardless of what the nameplate voltage is on the motor, UL is going to require you to test that UR motor as part of the compete assembly. That's why the UR motor is cheaper, there is no amortized testing cost in it. If you are an OEM and you are going to be making thousands of these machines that need an overall UL listing as a specific type of machine (i.e. one that has a UL category like a Packaged Air Compressor), then the UR route will save you some money. If you are building a one-off custom machine, or even if you are an OEM but only making a few, using a more expensive UL Listed motor will ultimately cost you a lot less.

"Will work for (the memory of) salami"

 

[stevenal]

Motors and controls go by the nominal utilization voltage (230), other equipment goes by the nominal system voltage (240). See ANSI C84.1-2006 2.4.1.

 

[magoo2]

There's a 2011 version but the differences won't affect what is being discussed.

 

[Eng8492]

Thanks all for the great information. Never realized that motors would should be a little different than relays tranformers switches etc until I couldn't find any "240 VAC" motors. Great info, thanks.

Regarding listing/recognition.. AFAIK, Listing is for a complete standalone product. Recognized components go into product to a listed product to minimize compliance issues.

 

[Eng8492]

Thanks all for the great information. Never realized that motors would should be a little different than relays tranformers switches etc until I couldn't find any "240 VAC" motors. Great info, thanks.


I dont understand the point about choosing a listed motor. My understanding is that UR (Recognized) is for components that meant to be integrated into a higher level product, and UL-listed is for a final complete product that is sold to an end-user. Use of recognized components significantly reduces the scope of investigation because the product ratings are "trusted". However, in some cases, additional testing of recognized components is required, for example, when seeking UL 61010-1 Safety, test conditions for dielectric withstand are at higher humidities than many specifications for recognized components.

 

[jraef]

You seem have it right, I guess I don't see your problem understanding it. Let's try this.

Let's say you are making a fish evisceration machine. There is no specific UL classification for them, so all you need is a UL listing on the sub components in the machine. You use UL listed motors for the knife and conveyors, a UL listed control panel and a UL listed pump assembly. Done.

But to try to save a few bucks, you buy the pump separately from the motor and buy a UR motor that is Recognized component motor for a pump. Now you have created a scenario wherein your motor must be tested and listed with the pump assembly you are using it with, so you have taken on that testing and listing cost of the recognized motor ON the pump in the operating conditions you specify that the pump mfr had done previously.

If you want to avoid that, you can get a UL listed motor, just like an end user would, and use it as you like, it will not need evaluation by itself used in that machine, because you are NOT selling the pump as a stand alone pump, you are selling a complete machine that USES a pump in it, and the electrical components making it up are all individually UL listed already.

Now let's say you were the pump mfr instead. Your motor choices are: 1) UL listed motor at greater expense and a risk that it you might have to retest it with the pump assembly if it requires its own UL listing as a specific type of pump on its own anyway; 2) UR motor that you definitely have to test with the pump or; 3) custom make your own motor from scratch, essentially an "unevaluated" motor. Of those 3 choices, #3 is the most expensive, because you are taking on the FULL task of designing, testing and submitting it to UL for destructive testing. Choice 2 is the lowest cost alternative as an OEM of a volume product, because the UR motor has been pre-tested and recognized as a component to be used on specific applications and conditions so UL will not require testing of the actual motor itself, only the entire pump assembly. Option 1 is only viable if the higher cost of the listed motor is less than the amortized cost of #2 depending on how many of these pumps you expect to sell. There is still a small chance that an inspector might say he wants the pump tested with that motor, but not a significant risk. But if you are only selling one or a few, it's often worth taking that risk.

"Will work for (the memory of) salami"