Is this chiller on R407C refrigerant? Are your sensors good and transducers good?
Has the refrigerant ever been removed from the system and then reused back into the system?
You mention three chillers, are they all showing the same symptoms?

 

Yes, it's R407C refrigerant, and we have three chillers "A " "B" and "C" having two circuits, system no.1 and system no.2.
Before this issue, the chiller "C" was tripping on antifreeze thermostat, as evaporator temperature was reaching 30 degree Fahrenheit, this 30 degree Fahrenheit was reaching only when system no. 2 starts. Rest of other two chillers "A" & "B" were performing well.

As I found, evaporator was scaled, I did the Descaling on the heat exchanger using rydlyme chemical by heat exchanger servicing professional, and then found the system was performing well, no more trip on antifreeze thermostat. And suction and discharge pressure was well maintaining. Delta T Between the cooler inlet and outlet was 14 degree Fahrenheit at full load conditions of chiller.

As we found, the result has been improved after descaling evaporator heat exchanger, we did the Descaling on other two chillers also, as this chillers were 16 years old and it was descaled before also three years back.

After 45 days of Descaling heat exchanger, it was observed that one of the chiller "C" system no.2, discharge pressure is 175 Psig , suction pressure going below 45 psig and now it's going up to 33 psig and tripping on low suction pressure at 29 psig after running for two hours or it trips after half an hour if ambient is 69 degree F.
And outlet of expansion valve and suction line
started icing up.

There was no leak in system, system was flushed with R141B & NITROGEN, filter drier & Txv valve of same size was replaced with new one but still same problem.

And, after this chiller "C" issue some two months passed away and the same problem started for chiller "A" & "B" also. Now, we have to kept one compressor off to prevent low suction pressure.

Note: This chiller has two compressors on system no.1 & two compressors on system no. 2.

On all three chillers "A" "B" and "C' System no.1 pressure is healthy suction pressure 60 to 70 psig.

And system no.2 is only affected on all three chillers. Why?

Chilled water line strainers cleaned, and checked water flow found normal 122 gal/min.

Now, with three compressors running Delta T is 6.5 degree F accross heat exchanger.

Superheat at system no.2 is 3 degree Fahrenheit.
And subcooling is 5 degree F.

Superheat at system no.1 is 16 degree Fahrenheit and subcooling is 10 degree F.

 

That is quite a tough question to answer without the following info.

Refrigerant type
Is there a fine mesh strainer at the entrance of the exchanger?
Entering and leaving water temp
Pressures
Superheat

If you had issue with the exchanger getting clogged I'd say follow the manufacturer recommendations and install a fine mesh strainer at the chiller entrance.
A good water treatment help a lot for plated heat exchanger

 

Yes, it's R407C refrigerant, and we have three chillers "A " "B" and "C" having two circuits, system no.1 and system no.2.
Before this issue, the chiller "C" was tripping on antifreeze thermostat, as evaporator temperature was reaching 30 degree Fahrenheit, this 30 degree Fahrenheit was reaching only when system no. 2 starts. Rest of other two chillers "A" & "B" were performing well.

As I found, evaporator was scaled, I did the Descaling on the heat exchanger using rydlyme chemical by heat exchanger servicing professional, and then found the system was performing well, no more trip on antifreeze thermostat. And suction and discharge pressure was well maintaining. Delta T Between the cooler inlet and outlet was 14 degree Fahrenheit at full load conditions of chiller.

As we found, the result has been improved after descaling evaporator heat exchanger, we did the Descaling on other two chillers also, as this chillers were 16 years old and it was descaled before also three years back.

After 45 days of Descaling heat exchanger, it was observed that one of the chiller "C" system no.2, discharge pressure is 175 Psig , suction pressure going below 45 psig and now it's going up to 33 psig and tripping on low suction pressure at 29 psig after running for two hours or it trips after half an hour if ambient is 69 degree F.
And outlet of expansion valve and suction line
started icing up.

There was no leak in system, system was flushed with R141B & NITROGEN, filter drier & Txv valve of same size was replaced with new one but still same problem.

And, after this chiller "C" issue some two months passed away and the same problem started for chiller "A" & "B" also. Now, we have to kept one compressor off to prevent low suction pressure.

Note: This chiller has two compressors on system no.1 & two compressors on system no. 2.

On all three chillers "A" "B" and "C' System no.1 pressure is healthy suction pressure 60 to 70 psig.

And system no.2 is only affected on all three chillers. Why?

Chilled water line strainers cleaned, and checked water flow found normal 122 gal/min.

Now, with three compressors running Delta T is 6.5 degree F accross heat exchanger.

Superheat at system no.2 is 3 degree Fahrenheit.
And subcooling is 5 degree F.

Superheat at system no.1 is 16 degree Fahrenheit and subcooling is 10 degree F.

Water treatment done by our mechanical department and found pH level above 6.

 

If the problem is found on all three chiller I'd say it might be a water loop problem.

When you say that you have 122 gal/min, is flow per chiller or for all three chiller?

How do you measure the flow?
If it's a gmp meter is it accurate?

Like I said in the previous reply, plated heat exchanger are really sensible to clogging if the manufacturer reccomandations are not followed.
The ask for some specific parameters to be maintained on the water side.
It is mandatory to have a fine mesh filter at the chiller entrance.

You can try to do a counterflow flush at the heat exchanger to remove any trapped particules.

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Hi Patpinet,

The problem is solved by replacing all the 3 BPHE COOLERS, and the chillers are performing well. Looks like coolers were internally clogged and loose efficiency due to ageing. Thanks all for exchanging your ideas and efforts.

 

Counterflow flush at the heat exchanger was done during descaling by heat exchanger service professionals by fresh water.

 

FLOW meter is checked by instrument department and found ok.

 

Evaporator approach?

 

Evaporator approach is 5 degree F with 75 % load. Only three compressor kept running. Compressor no.4 kept off to maintain suction pressure on system no. 2, if we run compressor no. 4 , system no. 2 trips on low suction immediately.

 

Evaporator approach is 5 degree F with 75 % load. Only three compressor kept running. Compressor no.4 kept off to maintain suction pressure on system no. 2, if we run compressor no. 4 , system no. 2 trips on low suction immediately.

 

Water or glycol?

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Can you fill a complete log sheet with pressure and everything.

I believe a YLAA log sheet can work out for you.
Take the flow measure at the chiller with pressure drop.

I'm not familiar with your specific chiller but I'm on jci site looking for info


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Please check the attachment for chiller readings received on site.

 

Glycol

 

What is the type and concentration?

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Ethylene

 

If you can measure concentration with a refractometer it will help a lot.

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Here's is a link to YLAA log sheet

https://drive.google.com/file/d/1YGyRkYKA63R2ha3uLJPtlaSrWQ3lwOsp/view?usp=drivesdk

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Ethylene

 

Has the R407C been removed from the affected systems and then re-charged back into the same system?

 

Yes, recharged, newly.

 

If all three chillers are experiencing the same fault, the problem is with the system that is common to all machines.

make sure your glycol solution is the correct concentration. if it's too strong (thick) you will not get the proper flow, due to lack of available pump HP.

also, might be a good idea to inspect your glycol pumps for wear.


not knowing your system, we can just speculate.......

you may have a valve that is not opening, even though you think it is, could have a plugged pump strainer, could have an inline pump failed, etc. etc.

 

Real quick like that I'd say your missing some refrigerant on the circuit 2.
Or its not the right refrigerant.

Do you have a sight glass and can you confirm that it's clear (free of bubble)

If not a clogged heat exchanger is a possibility, but only half of it doesn't make sense

 

circuit 2 gas was charged as per name plate, weight 18 kg for circuit 2, but still same problem, and liquid line sight glass with 18kg charge was found very white, & foamy.

 

Could also be an oil logged evaporator.

Or devider gasket blown out