HVAC Nameplate

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raider1 said:
My understanding is that you can either use an ampere rated disconnect in accordance with 440.12(A)(1) OR a HP rated disconnect in accordance with 440.12(A)(2), but you are not required to meet both.

Also a single air handling unit IMHO would not be a combination load and 440.12(B) would not apply.

Chris
Click to expand...

Are you implying that you do not need a HP rated disconnect?

I thought both were required 440.12 (A) does not say ampere or HP rating.
 
430.1 Scope.
This article covers motors, motor branch-circuit and feeder conductors and their protection, motor overload protection, motor control circuits, motor controllers, and motor control centers.

440.1 Scope.
The provisions of this article apply to electric motor-driven air-conditioning and refrigerating equipment and to the branch circuits and controllers for such equipment. It provides for the special considerations necessary for circuits supplying hermetic refrigerant motor-compressors and for any air-conditioning or refrigerating equipment that is supplied from a branch circuit that supplies a hermetic refrigerant motor-compressor.

In both above articles, the disconnecting means is sized at 115%.

Rick
 
augie47 said:
Back to square 1 for a second. The thread is entitled "HVAC" but the OP states air handler. Is some of this load compressor ?
If not, don't we need to be in 424 rather than 440.

Barclayd: Compressor or not ?
Click to expand...

Yes - compressor and fan.
More information available.
Compressor RLA 18.9 amps
Compressor LRA 146.0 amps
Fan FLA 5.8 amps
MCA 29.4
MOCP 45amps
Full Load Amps 24.7
It is a Packaged Unit - another section has the air distribution fans, but that has a separate feed.
db
 
barclayd said:
Yes - compressor and fan.
More information available.
Compressor RLA 18.9 amps
Compressor LRA 146.0 amps
Fan FLA 5.8 amps
MCA 29.4
MOCP 45amps
Full Load Amps 24.7
It is a Packaged Unit - another section has the air distribution fans, but that has a separate feed.
db
Click to expand...

IMO you would need a disconnect sized at

MCA 29.4 x 115% = 33.81 Amps per 440.12 (A) 1

LRA 146 Table 430.251 (B) @ 208 volts = 10 HP per 440.12 (A) 2

So IMO you would need a 60 amp disconnect rated at 10 HP

The disconnect should be able to be opened under locked rotor condition.
 
One-eyed Jack said:
Use the exception to 440.12(a) 1 Non fusible disconnect rated at 10hp. Don't worry about current rating.
Click to expand...

My first inclination was to spec a Heavy Duty 30a NF - 10HP rated.
I might still do that.
This does not seem to be one of the easier articles to interpret.
thanks all
MERRY CHRISTMAS
db
 
The typical 60a non-fused pullout is around $10.

"What, me worry?"
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