energy consumption is very high-centrifugal chiller

[moideen]

Our two buildings, assume building A and B. equipped Mitsubishi centrifugal chiller. The electrical consumption in 2015 as below mentioned. Capacity is approximately same. Now I am taking details to analyze the reason the huge consumption for building A. I already conducted the primary survey on building A. I found the building automation is out of order. Chilled water delta t is not maintained as design. (In building B also, the automation system is out of order). Now I am collecting all details to find out the cause. The problem is the same operation quality follows for two building. Except the condenser pump is placed in building in ground floor.so its power is high compare to building B. I will update more details. Your any comments on this really appreciated.

thanks
moideen-dubai

 

[moideen]

 

[EnergyProfessional]

how did you measure energy consumption? does it include pump, or just chiller, or the entire building?
I didn't double-check your numbers, but there is a 960 ton chiller plant with 960 gpm, how do you get 2 gpm/ton?
what are actual dT?

You say controls are bad.. i'd say fix that and ensure chiller operates as designed to begin with. then think of improvements.

 

[LittleInch]

Is this a reverse cycle system?

Is the hot (red) side for heat in winter and the green side for cooling in summer??

My comment is that we have virtually nothing to go on.

Is building A in the sun more?
Did the residents have the AC on for longer?
Did they have it cooler than building B?

There must be something major between the operation of the two buildings to be approx. 3times as much power.

What are you using for tonnes to kw consumed?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[willard3]

What are the uses/occupancies of the two buildings?

 

[317069]

What are the name plat capacity of the chillers compressors?
what are the numbers, 2708333, 879167, 14423077, 152243549 and what are the units (dollars, KW/H, ..etc.)

 

[moideen]

EnergyProfessional:960-ton total is capacity.960 gpm with two pumps. I have attached chiller and cooling tower details that copied from as built drawings.in, Dubai, ambient temperature will reach to 48c, wet bulb mat reach 93F.
Now winter started here, chiller works now in part load, delta t is 3.7f in chiller and CT range is 3.7F.

 

[moideen]

LittleInch : This centrifugal water-cooled chiller, red is water-cooled condenser. Both buildings are in same orientation. Both are five-year-old building. “ What are you using for tonnes to kw consumed?”-what you mean?

 

[moideen]

willard3 : both are fully occupied.

 

[BronYrAur]

You listed design Delta-Ts but what are the actual Delta-Ts? Also, does one system have glycol and the other not? What about set point temperatures, are they both the same?

 

[moideen]

Now the building load is low, the system works in part load. Actual delta T is 3.5F.i have planned to check the actual water flow rate in all pumps. also send the enquiry to carrier, train for submitting theier proposal for a chiller plant manager.

 

[BronYrAur]

Do you have any idea what the actual delta-Ts are on a design summer day? Given that the two chillers were designed at different temperature differences, the energy consumption may be able to be explained justdue to poor delta-T. Building A was designed for higher but may in fact be getting a lower temperature change than Building B.

Are these systems primary secondary, and if so, how do you maintain the primary secondary flow relationship?

 

[moideen]

BronYrAur: I am still waiting for the log sheet in summer (august) from my contractor. they would provide me soon. now the contractor fitting water meter in make up and blow down line to understand the actual water consumtion and performance of the ct.

 

[moideen]

i have a related question, that the pump name plate head is 70meter(233 ft). i checked the pressure gauge, discharge pressure is 215 psi and suction is 160 psi. so the total head is 127 feet, less than 103 feet from name plate. do you think any abnormality or over sized the pump?

 

[EnergyProfessional]

Pump has a flow/pressure curve, not a single pressure point. Depending on your system curve, flow and head will adjust along the pump curve (riding the curve).
The 70 m likely is the pressure at no or minimal flow.

 

[moideen]

EnergyProfessional: then what is the best method to understand whether the pump is over sized. next week ,i am goin to check real water flow rate. pump name plate flow rate is 1522 gpm and design flow rate is 960gpm. .i gooled to get the performace -cure sheet, but no available, i have requested to pump manufacture to get the performace sheet.

 

[EnergyProfessional]

If a pump is over-sized is hard to tell, depends on the design and how known the system pressure drops were, how conservative and good the engineer was etc. and what changed since then? Maybe they oversized for future expansion?
and are you operating as intended? for example maybe only two pumps should ever run and 3rd is reserve (N+1)? how do you know 575 gpm is the right number?
and again, in a 2-valve system flow will vary depending on load.

how do you intend to check the flowrate? What pump is it that the manufacturer doesn't have curves on their website?

too little information for us to judge, and i still think your schematic is incomplete, or that is a weird setup.

 

[lilliput1]

Check electrical diagrams to confirm which equipment is on which meter. Part of equipment for plant B could be on meter for plan A. Compare full load hours for each plant. They should be close to each other.
Full load hours = Annual kwh/(kw of chiller and auxiliaries)
Approx kw of chillers & auxiliaries = .5 for chiller + .1 for pumps + .1 for cooling tower = .7 kw/ton