Motor rating tag

[Logwilli]

I have an air compressor with an electric motor. The motor’s metal specification tag riveted to it reads 5.5 Hp and below that it specifies 120V, 15amp. It also has a 15amp plug. I am just a structural engineer, but even I believe this cannot be correct. Does this look suspicious to any of you electrical engineers?

 

[resqcapt19]

They use the fictitious "peak horsepower" in place of the actual horse power on things like cord and plug connected air compressors and central vacuum power units for marketing purposes is why we have Exception #3 to 430.6(A). This is a very common practice for that type of equipment.

Exception No. 3:
For a listed motor-operated appliance that is marked with both motor horsepower and full-load current, the motor full-load current marked on the nameplate of the appliance shall be used instead of the horsepower rating on the appliance nameplate to determine the ampacity of branch-circuit conductors in addition to the current ratings of the following:
(1) Disconnecting means
(2) Motor controllers
(3) Short-circuit and ground-fault protective devices
(4) Separate overload protective devices

 

[waross]

HP/CV
Yes, Steam Horsepower.
But a boiler HP is equal to about 13 Imperial HP.
Boiler HP was originally calculated on the heating surface in a boiler.
Boiler efficiency has increased by a factor of about 13 over the years.
Citroën 2CV, = 2 Steam Horsepower or 2 taxable horsepower. About 26 Imperial HP. (2CV4 = 4 wheel drive)

Boiler Capacities - The Engineering ToolBox
1 horsepower (boiler) = 434107 foot-pound-force/min = 13.1548 horsepower (mech) = 13.1495 horsepower (electric) = 13.3372 horsepower (metric) = 13.1487 horsepower (water) = 9809.5 joule/sec = 9.8095 kilowatt

5.5 CV is over 70 Imp. HP. From a 120V/15A supply we must be into over unity here.
(Yes, I know, over time CV has morphed into an abbreviation for a translation of Imperial HP.)
Further digression:
Michelin introduced and first commercialised the revolutionary new radial tyre design with the introduction of the 2CV.
Engine

​

375 cc H2 air-cooled 9 hp (7 kW).

​

425 cc H2 air-cooled 12 hp (9 kW).

​

435 cc H2 air-cooled 24 hp (18 kW).

​

602 cc H2 air-cooled 29 hp (22 kW)
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

My French teacher told us that the Citroën "Deux Chevaux" car meant "2 Horses" because the engine was so gutless.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

That's probably an honest mistake. grin
Quoting from the Citroën web site would have only got you in trouble.
That's the way it was back then.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!