anybody pls urgent

[balaji]

Hi friends,
Currently iam facing a problem in Chiller the supply chilled water temperature measured near the AHU is 16 degree celcius ( which should be 7 )the return is 20, the chiller was mainted by subcontracter and AHU belongs to me. I said the problem is in the chiller, but the subcon refused to agree and said the chiller is working properly, The problem may in the AHU as the return air temperature is high the chilled water supply temperature is also high is it true? if so how the delta T is 4 degree celcius ( i hope normally it should be 5.5 degree celsius )

my question is if the return air temperature is high is it possible to raise the CHWT to 16 degree celcius

if the subcon statement is correct as there are no proper airflow then there is no proper heat transfer also how come the CHWT rise then

anybody can fix this problem pls with proper justification

regards,
Balaji

[nike123]

What is AHU air temperature and RH% (or DB and WB) in and out?
What is AHU air flow?

[nike123]

my question is if the return air temperature is high is it possible to raise the CHWT to 16 degree celcius

Yes it is! Chiller could only maintain temperature difference! If flow is unchanged, temperature deference will be according to produced chiller power.
So, if you have same power output at 7°C water in and at 12°C water in, then acordingly, water out will be, say 11°C (4K delta) and 16°C.


if the subcon statement is correct as there are no proper airflow then there is no proper heat transfer also how come the CHWT rise then

If you don't have proper air flow then heat is not transferred from air to water in quantities to make bigger delta T of water in and out. Therefore your lower delta T than you expect (you expected 5.5K) but it could be also indication that you have too much water flow.


anybody can fix this problem pls with proper justification


Check airflow and air temperatures and RH for evaluation on AHU performance.

[Slatts]

Hi friends,
Currently iam facing a problem in Chiller the supply chilled water temperature measured near the AHU is 16 degree celcius ( which should be 7 )the return is 20, the chiller was mainted by subcontracter and AHU belongs to me. I said the problem is in the chiller, but the subcon refused to agree and said the chiller is working properly, The problem may in the AHU as the return air temperature is high the chilled water supply temperature is also high is it true? if so how the delta T is 4 degree celcius ( i hope normally it should be 5.5 degree celsius )

my question is if the return air temperature is high is it possible to raise the CHWT to 16 degree celcius

if the subcon statement is correct as there are no proper airflow then there is no proper heat transfer also how come the CHWT rise then

anybody can fix this problem pls with proper justification

regards,
Balaji
Balaji, if your chilled water supply temp is 16C, you're not going to get much cooling out of it. I would put the problem back on the chiller.
If it can't give you your 7C supply, the problem is not at your end.

[nike123]

Balaji, if your chilled water supply temp is 16C, you're not going to get much cooling out of it. I would put the problem back on the chiller.
If it can't give you your 7C supply, the problem is not at your end.

If problem is exclusively at chiller side than Chiller water temperature difference will be lower than 4°C.

[shamsheer]

how maney problems? the chiller compressor runs after 10 minits cut off again run again cut off why this problem coming reciprocating,100ton
compressor

[nicolacozma]

If water delta is 4K means the water flow is more than nominal flow and this is still ok.
If the chiller can`t go down more than 16 degree means the cooling heat exchanger from AHU absorb too much heat.
The chiller could be undersized or the return air temperature of AHU is to high.

regards

[nike123]

Water flow could be measured and actual cooling capacity calculated from that. Also, air flow at condenser could be measured and corresponding condenser actual capacity could be measured from that to establish is the chiller a problem.

[balaji]

Also, air flow at condenser could be measured and corresponding condenser actual capacity could be measured from that to establish is the chiller a problem.
How to measure and calculate can you brief me pls

[nike123]

Also, air flow at condenser could be measured and corresponding condenser actual capacity could be measured from that to establish is the chiller a problem.
How to measure and calculate can you brief me pls


By using anemometer and measuring air speed across condenser fins in few points and average speed is calculated. Then calculating area of condenser fins by measuring with and length of condenser . From that measured data you then calculate air flow by multiplying speed with area.
Or, you could use data about air flow from technical data of chiller if you are sure that fan is OK and at full speed and that condenser is clean.

Now you need to measure delta T of air at condenser and insert that in this handy software (http://hvac.507.com1.ru/chillers.ru/htdocs/download/programms/SIahuCalc3.zip) from our member Marc L O'Brien.
Lot of calculations could be done directly on his site:
http://fridgetech.com/calculators/

[yousufrafi]

I think your AHU inlet liquid tempreture is high. So i think your chiller is not pull down the temprature below 16 degree C .Or poor insulation on your hydronic cycle.

[HVAC Master]

Balagi, I would recommend analysis of design values, It should not be a single AHU there. Try to look what are Heat loads, chiller capacity, CHW flow rate through the pumps, cooling tower or ambient air temperature etc. With out it your question is not answerable