Stealing Little Bill's ac unit

[david]

Looking at 430.24 and 440.22
How did the manufacture come up with 18.9 min Circuit ampacity. The compressor Rla 14.1
Fan motor fla 1with a 1/6 hp motor table fla of 2.2

The manufacture took 14.1 rla × 1.25 =17.625.
The manufacture did not use the table fla of 2.2instead took the motor fla of 1fla.looking at 430.24 this confused me at first because the manufacture took the smaller fan motor fla of 1 × 1.25.

1.25 + 17.625 = 18.875
18.9 min Circuit ampacity

Anyhow I found it to be interesting how the manufacture applies article 430.24

As a side note say the compressor motor is 2hp with a rla of 14.1 @ 230 volts the table fla is 12fla

So you have a motor with a fla of 12fla under normal conditions. But because it is a compressor and the motor is being cooled it has a fla of 14.1 being identified as rla.

Ii also found it interesting that the term fla was changed in 1972 to rla for compressor article 440 motors

 

[mtnelect]

This is a common theme ... For Electrical Contractors !
HVAC is a different "Animal" ... Trust me.

 

[Eddie702]

Manufacturers don't use the NEC. They only have to get their units passed by UL or another testing agency. Manufacturers always put fictious HP rating on their motors they overate them. The amperages are usually correct though.

 

[mtnelect]

The one fact that throws everyone off is that ... It's not just a motor, it's a "Hermetic" motor. The "Suction" return cools the motor !

 

[david]

Manufacturers don't use the NEC. They only have to get their units passed by UL or another testing agency. Manufacturers always put fictious HP rating on their motors they overate them. The amperages are usually correct though.

I know the manufactures can do certain things not in accordance with the NEC.
Take a look at article 550. A lot of that article was written for the manufacture to follow.
In this example the manufacture did follow 430.24 except they applied the 125 % to both the largest and smallest motors in the group

 

[ptonsparky]

I would apply 125%. The motors start at the same time.

 

[david]

I would apply 125%. The motors sta
Start at the same time.

The data plates submitted by mtnelect the manufacture only applied the 125% to the largest motor

Both manufactures are in compliance with 430.24, I just find it interesting.

Also 430.
6(B) dosnt use the table fla, instead uses the name plate fla and that's what the manufacture seems to be doing

They all seem to be using the 225% max when it comes to 440.22 175%/225%