Calculating Tonnage of refrigeration machine

[batmon18]

Hello all, i'm an engineering intern trying to calculate the tonnage of an electric brine refrigeration machine. I read the info on the motor and it's a: 223 amp motor, 2300 volts, 900 HP. Anyone know how to calculate tonnage?

[US Iceman]

That will not work. You need to find the operating conditions of the refrigeration system and a copy f the compressor manufacturers performance data.

Anything else is just a wild guess.

[batmon18]

I have a list of real-time operating conditions:

Comp TEJ Bearing Temp Comp SEJ Bearing Temp Comp Thrust Bearing Temp Comp Oil Reservoir Press Comp Oil Temp Comp BRG Oil Supply Comp Back of Seal Oil Press Comp Oil Diff. Press Comp Discharge Gas Temp Comp Bearing Oil Supply Temp Gear/Motor Oil Supply Temp Motor Amps Cond. Enter Water Temp Cond. Exit Water Temp Cond Refrigerant Temp Cond Refrig. Press Evap Refrig. Press Brine Entering Temp Brine Leaving Temp Main Brine Loop Temp Evap Refrig. Temp Economizer Refrig. Temp Control Air Press Local Temp Set Pt. PID Out
I'm wondering if I can use the motor amps and voltage to get HP and use that to calculate tonnage..

[batmon18]

Sorry, here it is in list form:

Comp TEJ Bearing Temp
Comp SEJ Bearing Temp
Comp Thrust Bearing Temp
Comp Oil Reservoir Pressure
Comp Oil Temp
Comp BRG Oil Supply
Comp Back of Seal Oil Press
Comp Oil Diff. Press
Comp Discharge Gas Temp
Comp Bearing Oil Supply Temp
Gear/Motor Oil Supply Temp
Motor Amps
Cond. Enter Water Temp
Cond. Exit Water Temp
Cond Refrigerant Temp
Cond Refrig. Press
Evap Refrig. Press
Brine Entering Temp
Brine Leaving Temp
Main Brine Loop Temp
Evap Refrig. Temp
Economizer Refrig. Temp
Control Air Press
Local Temp Set Pt.
PID Out

I'm wondering if I can use the motor amps and voltage to get HP and use that to calculate tonnage..

[US Iceman]

all you need are these:
Cond Refrig. Press
Evap Refrig. Press

Convert the pressures to the saturation temperatures for the specific refrigerant used in the compressor. Now look these temperatures up on the compressor manufacturers performance charts. They list the compressor performance based on saturated inlet (suction) and condensing temperatures.

[batmon18]

all you need are these:
Cond Refrig. Press
Evap Refrig. Press

Convert the pressures to the saturation temperatures for the specific refrigerant used in the compressor. Now look these temperatures up on the compressor manufacturers performance charts. They list the compressor performance based on saturated inlet (suction) and condensing temperatures.

Great! Thanks so much for the help

[MeanMack]

Here is what I do. First you need to have the manufactures performance data at 25 different Suction and discharge temperatures. These are laid out in a matrix. 5 suction by 5 discharge. These will be shown as Tons of refrigeration and Brake Horse Power. By running these numbers through a nasty equation you can come out with that compressors performance at any given suction and discharge temperature. If the compressor has a VFD just use the speed as a direct multiplier. If the compressor is a screw and is running at a part load it is not a linear conversion. You would need to find out how the slide valve affects capacity at different positions. So 90% slide valve does not mean 90% capacity. There is a nasty equation for that too. Recips are linear.