chiller energy

[oly77]

Hi' guys What is the more important thing to conserve energy in a Chiller,100ton or 500ton THANK

[Randy S.]

Various ways to do that, based on outside temp, AHU load, system load, or manually run it up a few degrees in low load conditions. Get to know your whole system and find the times when you can carry the load with warmer chilled water.

Another issue is on start-up. Here again, know your system
and how long it takes to pull down to desired temps on start up, and don't bring on more capacity than you have to. Don't let that second machine come on line for a while to give you time to pull the loop down to temp. If you only have one machine in the circuit, sometimes you can limit capacity for a while on start up.

[RichardL]

Tower Water-Tower Water-Tower Water.
Assuming evrything else is in proper order, Ref. Charge, tube condition etc., The Condenser water temperature can increase the chiller load requirements by as much as 600%!!!
Running the tower water temperature as low as possible without suffering from oil migration or starving the evaporator of refrigerant is by far and away the most economical way of reducing the energy input to "Any" chiller..
With low tower water temperatures, several of us have documented with precision Watt-meters, that in several cases a condenser water pump was consuming more power that a given chiller, even tho' the chiller was producing 80% of its rated tonnage.
Understand that the condenser water pump is normally about 10% the Horsepower of the Chiller in question and you should understand that this is one helluva' savings...
Also understand that most makes and models cannot & will not tolerate low condenser water temperatures..
I'm beginning to sound like some sort of pencil necked sales weasel now.....
I ain't....Neither pencil necked nor a salesman.

[no8no3]

Richard...Once again you have pulled my tail feathers from the flame. I now have written proof from a viable source that lower condenser water temps actually do reduce loads.

My only problem with this is the particular location has a new RTWB beside an older carrier recip rack. If i drop the CWT, the rack does great, but the B compressor on the RTWB will drop out on low evap refg temp.

So my question to you is how to best optimize the rack without nuisance trips on the newer machine?

I would also like to know if since retirement is imminent, would you be available to my lawyers as an expert witness?
Ok, i,ve made some mistakes....

[acjourneyman]

Put lift control on it and the money will stack up instead of the refrigerant.

[RichardL]

no8no3,
I would advise a "Johnson Control" head-pressure controller to tie into your "Johnson Control" butterfly valve thru a "Johnson Control" pnuematic operator mounted to the entering condenser water valve with a "Johnson Control" mounting kit installed on the RTHB and set to whatever the minimum head pressure the B compressor will safely run at...
It's costing someone mucho' rubles to have the tower supply set so high on the Carrier compressors just to satisfy the RTHB.
Remember the basics for all time...
1- Work...T^he act of lifting "X" amount of weight an "X" amount of distance in an "X" amount of time.
2- Discharge Pressure minus Suction Pressure equals "Lift".

Lets "Assume" a given load on a given unit using R-22...
60PSIG Suction & 160# Discharge.
Lift equals 100#....
Same unit/load
Suction Pressure 60# and a Discharge Pressure of 260#.
Lift equals 200#..
It will now take "Twice" as much energy on the compressor to achieve the same amount of cooling...(minus the bare shaft current of course)
Regardless...The "Compressor Must" do twice the work to achieve stated results...
As I stated earlier, some units can & do operate safely with 55°f tower water....do the lift calculations and you can see how the condenser water temp. can effect the work by the compressor up to "600%"!!!

[hvac-tech-lane]

By Richardl

Lets "Assume" a given load on a given unit using R-22...
60PSIG Suction & 160# Discharge.
Lift equals 100#....
Same unit/load
Suction Pressure 60# and a Discharge Pressure of 260#.
Lift equals 200#..
It will now take "Twice" as much energy on the compressor to achieve the same amount of cooling...(minus the bare shaft current of course)
Regardless...The "Compressor Must" do twice the work to achieve stated results...

That would be absolute pressures, gauge + 14.7 PSI at sea level, correct?

[Randy S.]

But, of course, the added effort from the tower fans and water/chemical consumption has to be figured in. In other words you will save a lot of money, just not quite as much as the salesman would like you to believe.

[RichardL]

Originally posted by hvac-tech-lane
By Richardl

That would be absolute pressures, gauge + 14.7 PSI at sea level, correct?

You may use absolute pressure in the "Lift" equation if you so desire, but regardless if it it absolute pressure or PSIG, the results will always be the same.
As long as "Both" pressures are read the same, the results are always the same.
We were not discussing "Compression Ratio's"..

[chiller mekanik]

I agree, lowering the tower water as low as your machine can stand it is a very good way to reduce energy consumption.
Another thing that we've been doing is helping customers get the most out of one chiller before bringing on the next one.
I've found plants that bring on the second chiller ( add additional chillers ) when the first one is @ 80%, and then they won't shed the second chiller until the machines are less than 50%.
I've also seen the same logic applied with delta t in cases where there is no kw meter, if the delta t is more than 80% of the design delta t, you get the picture.
This method consumes a pile of energy as well.
Bringing on a second machine if you don't need it also increases energy consumption because of the extra circ pumps.
Unless you need more flow you don't need another chiller until the first one is wound out.
Another thing that helps is to make sure the machines are at design conditions.
Make sure the operators know what the delta t & p is suppose to be at all times so that changes in operation can be detected asap.
I see energy consumption evaluations as a very good tool for finding business oportunities.

[gmcd]

And start with the chiller that is used the most, and use some of the above noted advice re: condenser water temperature control. Also check chilled water temperature reset depending on load conditions - the higher the CHWS temp can be allowed to run, the more efficient the chiller operates compared to peak conditions.

[hvac-tech-lane]

Originally posted by RichardL

Originally posted by hvac-tech-lane
By Richardl

That would be absolute pressures, gauge + 14.7 PSI at sea level, correct?

You may use absolute pressure in the "Lift" equation if you so desire, but regardless if it it absolute pressure or PSIG, the results will always be the same.
As long as "Both" pressures are read the same, the results are always the same.
We were not discussing "Compression Ratio's"..

Interesting, thanks for the reply.