Motor not listed in the motor tables

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kevinware

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Louisville, KY
Ok everyone this may be an easy one, but I am an apprentice and I am still learning so go easy on me......

I have a motor with name plate info. as follows:

115 Volts Single phase
7.9 Amps
2/3 horsepower
60 Hz
no service factor listed
40 degrees temp.

My lead man wants me to try and figure out what we need to do to install this motor NEC compliant. It will be installed as a blower motor in a drop ceiling that will draw hot air out of a data center, duty will be continuous.

I looked for at the motor table 430.148 and found no 2/3 horsepower motor. If the motor is not listed how do I come up with good full-load current value to calculate my OCPD with? Can I use the 7.9 amps? Or just reaching, can I use the 1/3 horsepower rating and multiply by two?

Thanks Kevin
 
Re: Motor not listed in the motor tables

The problem I'm having is the 2/3hp rating. It is definitely not a NEMA standard. I'd like to know if the motor has any other info on the nameplate; specifically if it is possibly a UL recognized motor (backward "UR" symbol) or if it mentions that is is a NEMA or IEC based design.
 
Re: Motor not listed in the motor tables

Is this an actual motor (i.e., have you read the nameplate), or is it a made-up situation intended to assist with your training?

Multiplying the 1/3 HP value by 2 would not be appropriate. It would give you an answer that is higher than you need. That would be safe, but would give you an unnecessarily large wire.

I am not certain if you would be allowed to interpolate in this situation. 430.6(A)(1) allows interpolation if you have the nameplate amps but do not have a nameplate HP. That is why I asked if you have seen the nameplate.

I did a quick interpolation, just to see how it would turn out. Here is my process:
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  • <font size="2" face="Verdana, Helvetica, sans-serif">The table shows 9.8 amps for a 1/2 HP and 13.8 amps for a 3/4 HP. That is a difference of 4 amps, over a difference of 0.25 HP.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">A 2/3 HP is between 1/2 and 3/4. In fact, it is 0.17 HP higher than the 0.50 (i.e., the 1/2) HP.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Take the 0.17 (the HP difference between the 1/2 and the 2/3), divide it by 0.25 (the HP difference between the 1/2 and the 3/4).</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Multiply this by 4 (the amps difference between the 1/2 and the 3/4).</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Add this to the 9.8 (the amps for the 1/2 HP).</font>
<font size="2" face="Verdana, Helvetica, sans-serif">I get a result of 12.5 amps. I just don?t know if you can use it.
 
Re: Motor not listed in the motor tables

Yes Bob, this motor is UL listed, it does have a backward "RU" on the name plate. I will try to re-create the name plate:

Volts 115 Hz 60 Amps 7.9
RPM 1550 SP PH1 cap
Ins. CL AMB degrees HP 2/3

I believe the modle number of the motor is:
HE2J081N

Thanks,
Kevin
 
Re: Motor not listed in the motor tables

Actually the motor is not "listed," it is a "recognized component." That means it must be used as part of a specific "assembly" for which it is recognized; in this case, probably the blower.

The blower assembly installation instructions, or the "label" on the overall assembly, should specifiy the minimum conductor size and overcurrent protection.
 
Re: Motor not listed in the motor tables

If it is a blower, and not just a motor, I believe that 430.6(A)(1) Exception 3 might apply. It says if an appliance is rated both in hp and amps, you are to use the amps for sizing wire, disconnect, and OCPD.
 
Re: Motor not listed in the motor tables

Ok Rbalex,
The manufacturer of the blower assembly is Penn Ventilation Co. Model # Z12HTDA. I looked them up on the web and found them (imagine that). I downloaded a operation instructions & Parts manual and found this entry:

Electrical Connections:
1. Connect motor per nameplate to correct power supply.

2.Install all wiring, protection and grounding in accordance with NEC and OSHA.

3.Follow all local electrical and saftey codes, as well as the NEC and OSHA.

4.In order to prevent motor failure when speed controller is used unit must be started on High speed before turning to low.

So with reading this is it safe to say that number 1. is telling me I can use the name plate rating amps of 7.9 to size my overload, wire, OCPD?

Thanks,
Kevin
 
Re: Motor not listed in the motor tables

Kevin,

jtester has cited the correct Code Section.[430.6(A)(1) Ex 3] and you have arrived at the correct application - use the motor full-load current (7.9A) for all calcs.

Bob
 
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