Sizing OCP With Limited Name Plate Info

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Little Bill

Little Bill

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I have been asked to help another electrician hook up a piece of equipment but the name plate doesn't have all the info I think I need. The equipment is a cooling unit for a container, I call it a "reefer" unit. The voltage required is 460V 3Ø and the only other info on the plate is LRA:77A.
I don't know how to determine the FLA with just that info. I can figure the OCP if I could get the FLA. Another thing is the voltage on-site is 240V/120V 3Ø. So I know it will require a transformer but can't order one until I can get the missing info. Is there a way to figure what's needed with this little info?

The equipment is used and the customer didn't get any info. I tried to look up the unit but didn't come up with anything.
 
There's gotta be some other info, like MCA/MOC. Otherwise, someone needs to call the manufacturer.
 
Little Bill said:
I have been asked to help another electrician hook up a piece of equipment but the name plate doesn't have all the info I think I need. The equipment is a cooling unit for a container, I call it a "reefer" unit. The voltage required is 460V 3Ø and the only other info on the plate is LRA:77A.
I don't know how to determine the FLA with just that info. I can figure the OCP if I could get the FLA. Another thing is the voltage on-site is 240V/120V 3Ø. So I know it will require a transformer but can't order one until I can get the missing info. Is there a way to figure what's needed with this little info?

The equipment is used and the customer didn't get any info. I tried to look up the unit but didn't come up with anything.
Click to expand...

The nearest I can find is a Carrier Transicold semi-hermetic compressor with an LRA of 71 amps @ 208/230V voltage.The rated load amps is in the range of 12.4/19.3 amps! Here
 
topgone said:
The nearest I can find is a Carrier Transicold semi-hermetic compressor with an LRA of 71 amps @ 208/230V voltage.The rated load amps is in the range of 12.4/19.3 amps! Here
Click to expand...

Thanks! That's more info than I could come up with. I know it's not exact but maybe I can at least get a load calculation for the POCO. Then maybe I can contact the mfg to see if they can help.
 
synchro said:
I found the following service manual from Carlyle, who supplies compressors to Carrier. I don't know if it's the same as the one you mentioned, but on pg. 103 they show model DA0600 with:

Voltage 460V
MCC 27.8A
RLA 19.9A
LRA 77A

https://www.google.com/url?sa=t&sour...​​​​

Model BA0600 on pg. 105 has the same electrical parameters.
Click to expand...

What is MCC?

Never mind, it is in the legend at the bottom:slaphead:
MCC=Max Continuous Current
 
Little Bill said:
What is MCC?

Never mind, it is in the legend at the bottom:slaphead:
MCC=Max Continuous Current
Click to expand...

Is MCC the same as MOCP?
If that's the case then looks like the wire size for 19.9A would be #12 and max breaker on 27.8A would be either 25 or 30A. I don't know if you're allowed the "next size up" on motors/compressors or not.
 
Little Bill said:
Is MCC the same as MOCP?
If that's the case then looks like the wire size for 19.9A would be #12 and max breaker on 27.8A would be either 25 or 30A. I don't know if you're allowed the "next size up" on motors/compressors or not.
Click to expand...

MCC = maximum continuous current. The compressor is tested by lowering the supply voltage in steps. The motor will experience an increase in load amperes as the compressor load will demand higher amps as the voltage is lowered. The MCC is the value of the motor amps when the motor control trips out!
To add:
You will get the
RLA (rated load amperes) by dividing the MCC by 1.4 per UL 1995.
27.8/1.4 = 19.9A! See UL 1995 section 23.11 Here
 
Last edited:
topgone said:
MCC = maximum continuous current. The compressor is tested by lowering the supply voltage in steps. The motor will experience an increase in load amperes as the compressor load will demand higher amps as the voltage is lowered. The MCC is the value of the motor amps when the motor control trips out!
To add:
You will get the
RLA (rated load amperes) by dividing the MCC by 1.4 per UL 1995.
27.8/1.4 = 19.9A! See UL 1995 section 23.11 Here
Click to expand...

So how would you size the MOCP and MCA using the MCC=27.8 & RLA=19.9?
 
ramsy said:
Whats wrong with using 440.22(A) 175% of RLA
Click to expand...

I knew that much but the legend I saw said RLA=running load amps
440.22(A) says "rated-load current" and I didn't know if the two meant the same.
Too much confusing terminology between different mfgs and code.
 
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