# Thread: kw per ton w/vsd

1. EFFICIENCY
In the English l‑P system, chiller efficiency is measured
in kW / ton:
kW / ton = kW input
tons refrigerant effect
In the Sl Metric system, chiller efficiency is measured
in Coefficient of Performance (COP).
COP = kW refrigeration effect
kW input
kW / ton and COP are related as follows:
kW/ton = 3.516
COP
COP = 3.516
kW/ton

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EFFICIENCY
In the English l‑P system, chiller efficiency is measured
in kW / ton:
kW / ton = kW input
tons refrigerant effect
In the Sl Metric system, chiller efficiency is measured
in Coefficient of Performance (COP).
COP = kW refrigeration effect
kW input
kW / ton and COP are related as follows:
kW/ton = 3.516
COP
COP = 3.516
kW/ton
I think kw/ton and COP are two ways of describing the same thing only inverse of each other. kw/ton is" motor kw divided by tonnes of refrigeration."
Where as COP is" kw refrigeration divided by motor kw."
kw Refrigeration is tonnes x 12/3.41

Jay, most 19XR's or YK with VSD will show power factors of 0.95-0.98.
A power factor of 1.0 or greater will damage a motor windings. It wont matter much to the calculations.

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Power Factor can "Never" be greater than 1.
A power factor of 1 indicates a purely resistive load.
The power factor we always see would properly be stated as .95lag-.98lag ect.
Going beyond a unity power factor of 1 results in the forbidden realm of "Leading power factor",(Capacitive load) again always less than 1, and would be stated as .95lead-.98 lead.(example)
Please...No more references to "Greater than 1 power factor"...It just ain't there...

4. GREAT!!!!!!!!!!!!!!!!!!!

Originally Posted by jayguy

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Are the power factors of these devices close enough to 1.0 that a capacitor is not needed on the secondary of the contactor? I would expect to find a power factor improvement capacitor on every device but I haven't seen a single one. Also, since it would only be active when the device was running and would be on the 240 VAC line with the rest of the branch circuits, I don't see any detriment to installing one at each chiller.

Thoughts?

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Originally Posted by jayguy
Damn Jay, you got me sidetracked and I forgot what this thread is about!!!

7. Originally Posted by R123
Damn Jay, you got me sidetracked and I forgot what this thread is about!!!
i forgot i did that too!

8. Originally Posted by Priya1956
Are the power factors of these devices close enough to 1.0 that a capacitor is not needed on the secondary of the contactor?...
if you are talking about a vfd/vsd type of system, then you generally don't need or want a Power Factor Correction Capacitor between the line side of the drive and the utility. you definitely don't want any PFCC's between the drive and the motor.

Originally Posted by Priya1956
...I would expect to find a power factor improvement capacitor on every device but I haven't seen a single one....
PFCC's have a lot of great things going for them, however, they are generally misunderstood and/or misapplied. PFCC's can cause a harmonic resonance in the power wiring of the system if they are not engineered properly...this generally doesn't happen, but it can.

Originally Posted by Priya1956
...Also, since it would only be active when the device was running and would be on the 240 VAC line with the rest of the branch circuits, I don't see any detriment to installing one at each chiller....
i have seen many instances where they were sized for the chiller, installed AT the chiller but on the wrong side of the contactors (in a non-vfd chiller). this allowed for Power Factor Correction for the whole plant when the chiller wasn't running. every once in a while....BOOOOM.... and then every maintenance person running around like crazy. there are generally 2 different ways to install PFCC's and a 3rd hybrid which is what i like.

1. install a big power factor bank at the utility entrance...the good: corrects for the whole building to 95% or so...the bad: only helps the utility, the building doesn't get any benefit except for a lower utility bill (which is nice, but there are other benefits that are missing)

2. install a PFCC at every end device...the good: allows for better voltage regulation throughout the facility and a lower utility bill....the bad: high install cost and higher maintenance costs.

3. install a PFCC at all of the non-vfd major loads (chillers, pumps, fans) and install a smaller PFCC bank at the enterance...the good: better voltage regulation throughout the facility, lower utility bills, lower overall costs, the PFCC bank can still be used to perform a final correction to 95% or better...the bad: still has a high cost per device but not as bad as Option #2.

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The hybrid approach seems best especially as it improves power factor only on demand without the risk of overcompensation. Sounds like the big hurdle is quantifying the benefits beyond a reduction on the utility bill. How to put a \$ value to better voltage regulation?

Assuming that the capital cost of the PFCC is recovered only from a utility bill reduction, what is the typical payoff period for a device installed PFCC? Perhaps it is too long for owners to spend the capital up front??

10. the benefits are difficult to quantify. like you said, you are helping them with 'savings' which is a negative cost and very difficult to prove. you are usually going to find the only customers who want this are large users, people who understand the benefits and those that are already having problems.

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