How come these units’ nameplates will ALWAYS quote the fan(s) hp on the nameplate, but never the compressor(s) motor hp?
Usually states the minimum circuit ampacity for the entire chiller - don’t know why you’d want the compressor HP, you’re going to size your electrical feed based on the MCA.
Oh, one other reason - you can replace each fan motor individually if you need to. Not something you will do with a hermetically sealed compressor.
That makes sense, but for a field survey, i was looking for all motors’ hp data on the unit’s nameplate. Perhaps what you say is really why. So, if they were made to be interchangeable, like a pump’s motor, then you’d WAG it would be stated on the nameplate, at least some of the time? More importantly, will the unit’s model number or serial number help me get at this info?
It (the model number) should, if you can get the manufacturer information. You’d think this would be easy to get, but not always - I’d tend to spec Trane equipment because they made their information so easily accessible. . I’m sure Carrier makes good stuff but I never spec’ed it because I couldn’t get the data easily. Trane puts it all on their website.
On the other hand, consider what data you want on a field survey. The maximum load the chiller can present or the actual load it is at a particular time? Flow rates, Delta T, and circuit transducers can give a better idea of the real load. A chiller may or may not run at full capacity most of the time - what exactly are you trying to find out? That’s the question you should be asking yourself.
The FLA or RLA of the compressor motor is on the nameplate, yes?
Use that and the rated voltage to calculate kw. Convert to horsepower if you feel the need to be all 19th century.
KW=V x A x PF
Unless power factor is also specified as 1.0 then
KW =/= V x A
And given that refrigeration equipment often is designed toward commodity pricing, PF is often below .8 and I have seen really cheesy chinese bottom dollar stuff down around .6. Large, heavy, commercial, three phase stuff typically has better (higher) power factor.
Beyond power factor, motor and compressor efficiency will vary considerably, which you can’t see from electrical power calculations. Using KW for electrical power, and HP for mechanical power may be so two centuries ago, but it is a useful distinction to maintain.
For a chiller, you’d want to compare overall efficiency in terms of BTU/WH, or refrigeration tons/KW. Note that the first is in units of work/work, the second power/power. In refrigeration work it is easy to get crossed up between work units and power units…I frequently see equipment advertised with BTU ratings when BTU/H is what is meant.
That said, you can’t get to the shaft of a hermetic or semi-hermetic compressor unit, so if you know the electrical input requirements, and the ton rating on the refrigerant side, you don’t really need to know how much mechanical power is being moved from the motor to the compressor. A quality manufacturer might prefer not to spec this, because if their compressor is more efficient, then the HP number could well lower for the better unit. A crappy manufacturer, with an inefficient compressor design might well tout their HP number.
Note that in the above paragraph, I am using the term “compressor unit” for the combination of a compressor and motor, while this would normally just be called a "compressor " in the (non automotive) refrigeration trade.
I have never seen fan name plate data on a chiller. Don’t know why it would be there? Usually a chiller name plate will have the voltage and the amps. Also the hp of the compressor would mean little to the man in the field, he will want the tonnage of the compressor.