What size OCD?

[tom baker]

Re: What size OCD?

Its sixed per the ul listing as an appliance so it can be rated at 100% of the branch circuit, is it rated at 120V or 125V?

 

[bill addiss]

Re: What size OCD?

An 1875 watt hair dryer is about 103% of a 15 amp circuit

Bob,

For some reason these Hairdryers specify 125v.
1875/125 = 15 amps on the nose. I think they're finally at their limit now.

I'm not a fan of these hairdryers at all.

Bill

 

[templdl]

Re: What size OCD?

Since you brought that up have you notice that vacuum cleaners for the home that are usually used on a 15a circuit seemed to have peaked out at 12a. That's 15a x 80%=12a

 

[bill addiss]

Re: What size OCD?

Hmm,

I think Hairdryers have maxed out, but then again ...


Bill

 

[tom baker]

Re: What size OCD?

I'll use that in my classes when I discuss the maximum load on a branch circuit

 

[tom baker]

Re: What size OCD?

Homework Assignment:
Go to a big box hardware store. Look at the "5 hp" air compressors, with a 15 amp cord cap.
Note that the nameplate does not list FLA, it may say "special". Note that the NEC table value for a 5 hp 1 ph air compressor is 56 amps.
Is this a 5 hp air compressor? Maybe at locked rotor current. It is the maximum size motor to be able to run on 15 ampere branch circuit.
What sells air compressors? HP....
For a real 5 hp air compressor look in a Graingers catalog.

 

[gwz2]

Re: What size OCD?

Just today, copied the nameplate data from an Air Compressor.
Several decals on the unit noted 7 HP.

The Name plate data did not list HP. It did list voltage as 230V 1 PH 17.3 Amps. plus other data.

I do not have the 2003 UL White book at home to check against the 2002 UL White book.

Under (AALZ), which is at front of the numbered pages, and under "Sizing and Ratings" it notes that "Marked ratings of utilization equipment include ampere, wattage or volt-ampers ratings. Motor-operated utilization equipment may also be marked with horsepower rating. The actual marked ratings( other than horsepower rating ) and other markings or instructions, if any, are to be used to select branch circuit conductors, branch circuit overcurrent protection, control devices and disconnecting means."

So, don't install per the HP size, but per the amps or the watt or VA ratings.

T430.148 for a 230V, 17.3A would be consided as 3 HP +/-.

How deceitful these product promoters can be!

Several years ago, a similar installation for an Air Compressor. With-out looking-up the incident, I believe it had the same nameplate data as this unit today. The installer had used Number 10 AWG ( Cu ) on a 35 to 40 foot Branch Circuit. The owner called me back about a year later to tell me that the manufacturer, after burning-up two motors, told him to read the instructions, which I do not remember being on site at time of inspection. The owner had the instructions saying that Number 8 AWG ( copper ) must be used if branch circuit greater than 25 feet. The installer was contacted and I did not hear anything more.

gwz2

[ November 14, 2003, 06:36 PM: Message edited by: gwz2 ]

 

[tom baker]

Re: What size OCD?

gwz2, thanks for the quote from the UL White Book. Every electrican should have one, it really is part of the NEC, as Charlie has pointed out.
7 HP? I have never seen a 7 hp motor
Your comment about using the VA for determing the branch circuit size is correct for the NEC, as the NEC allows the motor VA rating to be used where it is marked in both hp and VA. This was a 1999 NEC change, as inspectors were requiring large branch circuits for "2 HP" garage door openers, that are not 2 hp.

 

[templdl]

Re: What size OCD?

With some of those HP rating one would think they are smoking those funny cigarets. And how about those shop vacs and portable electric tools with ridiculous hp ratings.... Although not a sure way to compare the power of this type of equipment the amperage rating lable of the device may be a somewhat better way to compare and apply.
That's why NEMA rated motors provide some sort of standardization for application and comparison. At least from what I can tell from the NEC they have classified motors in part by their HP, such as art 430-32, multispeed motors, Wye-Start delta-run, part-winding, etc, the actual circuit sizing and protection is based upon ampacity.

 

[Guest]

Re: What size OCD?

Here's a pretty good explanation of how the Hoover folks sugar coat amperage:

Efficiency Rating
There are two completely different ways to rate the efficiency of a vacuum cleaner. The most important way of stating the efficiency has to do with rating how well a vacuum cleaner filters the air to remove dust and allergens. The HEPA and ULPA specifications use this type of rating. The other way of viewing the efficiency rating has to do with stating the cleaning effectiveness relative to the amount of power being used to produce it. A great deal of confusion exists as a result of an efficiency and performance rating which The Hoover Company uses as described in our article on Efficiency and Performance Ratings .

Power of the Vacuum Cleaner Suction Motor

 

[iwire]

Re: What size OCD?

I do not know if we can compare the motors in small appliances like drills, some compressors, vacuum cleaners etc. with the motors in the NEC tables.

I may be wrong and show me the light if I am but aren't those charts for induction motors.

The small appliances use universal or series motors with brushes.

These pack more power in a small package.

I think another thing to consider is when we get a motor that says 5 hp it means 5 hp all day long most times.

The appliance motors usually say X hp peak.

So yes they can produce that hp for short durations but will soon smoke if pushed that hard continuously.

Here is a 1 hp universal motor with a FLA at 120 volt of 12.1 amps.

Info here


Here is a 1 hp induction motor with a FLA at 120 volt of 15.0 amps.

Info here

Look here and maybe here for more info.

 

[hillbilly]

Re: What size OCD?

Nice illustration. If that weight was 550lbs. and that horse could walk forward at a velocity of 1 foot per second he would be delivering 1 constant horsepower.
steve

 

[big john]

Re: What size OCD?

It's nice to see the concept of appliance ratings discussed here (even if it is off topic

-John

[ November 16, 2003, 12:21 PM: Message edited by: big john ]

 

[templdl]

Re: What size OCD?

What would be nice to see is a standard that these vacuum cleaner, small power tool, etc. manufacturers to use in order to advertise these HP ratings. At least NEMA is a standard. Straying away from that standard you get the Taiwan motor HP that are commonly found on woodworking machines and dust collectors for example, i.e. the same dust collector using a 2hp non-NEMA motor, 2HP based upon what?, often may be found with a 1-1/2HP NEMA motor. Is 2HP better than the lesser 1-1/2HP?
And those air compressors HP ratings for the home work shop, that another story.

 

[gwz2]

Re: What size OCD?

Once, a Rep for a pool filter recycling pump told me when I asked why the 2-1/8th HP motor only required 12 amps, replied " If the customer wants a Cadillac, we'll sell him a Cadillac, but the pump only requires a 3/4 HP motor to deliver the rated flow."


I guess that HORSEPOWER SELLS !!!

gwz2

 

[tonyi]

Re: What size OCD?

Its the same scam with computers. Consumers buy high mhz numbers thinking more mhz is always faster (not true). Higher RPM drives must perform better than lower RPM right? (not if they've reduced the platter and head count to keep the price down!)