chiller not performing R410a

[nike123]

c is specific heat in W/kg for water. And yes, it will be different for glycol.

[frank]

C = Specific Heat Capacity = 4.18kj/kg for pure water. Have a read up here
With glycol/water mix , the Specific Heat Capacity would alter depending on the concentration.

[Gingerair]

Specific Heat Capacity of Water ??

Moondawn, don't forget to insulate your temperature probes when taking readings..

That's my tupence )

.....Missed second page of thread...dooh !

[Gary]

A engineer attended today and the weather was not as hot as when i was last there, this is the details he gave me:

arrived on site found both compressors running with a chilled water flow temp of 14C and a return of 19.5C.

Carried out non condensables test and confirmed none were present.

Cleaned Condensor Coil Checked pressure before and after But no difference.

Discharge pressure with 1 compressor running was 22 bar (R410a) and with 2 compressors increased to 25bar.

Discharge temp way 61C
Liquid temp before expansion valve 34C
Liquid temp after expansion valve 22C
Suction temp 13.6C

Liquid pressure before expansion valve 23bar
Liquid pressure after expansion valve 16bar
Suction pressure 9.3bar

Air in to condenser 15C
Air out of condenser 35C

35C - 15C = 20K dT. This should be no more than 16K and preferably less. Clean or not, the condenser is not getting enough airflow.

Make sure the blade is clean, turning in the right direction, scooping the air and not backhanding it, the right motor and fan blade, etc.

[moondawn]

think it may be worth jet washing the condensor to try to totally eliminate bad airflow on condensor the unit is outside in a compound so this would be easily done.

cheers gary.

[mad fridgie]

Been away in Aus for a few days.
I think a bit of design knowledge is required (i do not know the plant )
Firstly FLI 75Kw, more than likely means Full Load Input
This equates to 2 Copeland ZB 385 (or equivilent)
The Duty of 155KW indicates that the design SST would be around 1C and SCT woukd be around 47C (15C split at 32 ambient) all within a couple of %
Your SST is some what higher, so your actual cooling duty is greater than the 155Kw, just short of double if SCT remained constant! But your condensor will have been sized for design heat of rejection, so the SCT will rise, and reducing the capacity at your present SSTs (but still greater than the design duty) You are greating large fluctuations in duty because you are getting large swings in air "on" ambients temps.
Depending upon the make and style of your PHE you can have an internal distributor, hence giving this elevated pressure and temp after the EEV but before the evap.
All data indicates that the machine is doing what it should for the conditions it has.
Maybe you could give us some data on the load "what is the final thing it is cooling"

[mad fridgie]

think it may be worth jet washing the condensor to try to totally eliminate bad airflow on condensor the unit is outside in a compound so this would be easily done.

cheers gary.

Not the problem

[mad fridgie]

What is the chiller water cooling.

[moondawn]

hi mad fridgie thank u for your replies, the other engineer has given this extra data for you:

It is cooling data rooms in a college but also possibly classrooms as well (although the site staff aren't too sure)

Do the design operating parameters depend on the duty of the load? Or for all high temp applications is the SST around 0/1°C and the condensing temp the maximum ambient air expected i.e 35°C.

It makes sense that there is an internal distributor fitted to the PHE but i'm not sure there is.

I've looked in the manual and it doesn't mention anything about the PHE

[mad fridgie]

Hi, I do not know your partcular machine and how it was designed, but if this is designed as standard air cond chiller, it is likely rated at 12C water on and 6C water off. The SST needs to be less than 6C.
I do have data on copeland compressors, so taking into account all the data you have given me, i am able determine some sort of basic design conditions.
Remember a nominal design duty, is just that "nominal" and is given at fixed steady state condition. If your condtions change so will your machine performance.
Your load, has there been any extra equipment installled in the data rooms, or extra air handles installed.
How old is the application, how many years have they had of trouble free cooling.
Is there a new control system or a new person managing the control system.
"Example only of what could be happaning", maybe the client is turning of all the air handles at night, (data transfer is minimal) during the night the data rooms build up some residual heat. When it is fired up in the morning a large load now exists.

[moondawn]

hi mad fridgie, the site is fairly new to us and therefore we are unsure what areas the chiller is feeding, also no one has been back to site since so will have to update at a later time


cheers lee