Is the compressor low on refrigerant gas (R-134A)?

[baghu]

Hi everyone,

I have a 0.25HP Mitsubishi Electric, hermetic compressor equipped, inline aquarium water chiller. It is only 6months old. Previously it used to cool down 1 degree C (From 26C to 25C) in just 20minutes when the ambient room temperature was as high as 36C. Also the compressor (hermetic tin can one) made a whirring sound like that of a petrol car engine or like a fridge compressor. The compressor's outer covering was very hot to touch previously. Blower blows out hot air from the condenser.


Nowadays, the compressor takes 3 full hours to cool the same amount mentioned above and also, now the ambient room temperature is only 28C.
The compressor makes little or no noise nowadays but it vibrates indicating the motor is spinning well and fast. Seems like the compressor is under very little load of gas pressure
The compressor now runs very cold (a bit warmer than the room temperature). Blower blows the same hot air as before.

I clean the condenser and air filter regularly. Condenser blower is running fine.

I have also cleaned the internal titanium evaporator coils, where the water is circulated by a pump. I used vinegar (2% acetic acid) and soaked for several hours and used high pressure water to rinse it.

What do you think is the problem? Is the compressor low on refrigerant gas or the evaporator coils are still clogged with debris creating an insulation?

Thanks everyone.

[chillerman2006]

Hi baghu

I used to look after cooling for huge aquariums for international artic research

the main issue was contamination of the heat exchangers from the salt water

I presume your aquariums are sea water and not fresh

we installed by-pass circuits so to enable the other hx

one hx could then be removed and sent away for chemical cleaning about every 3 months

R's chillerman

[baghu]

Thanks for the quick reply friend. But the water is freshwater.

[chillerman2006]

Hi

ok that rules that out then, unless hard water and scaling ?

maybe you can take some temps at diiferent points on the system to give us a better idea what it is doing

compressor in and out and after condensor

also air on and off condensor

the compressor sound could indicate its worn or your bringing liquid refrigerant back

R's chillerman

[baghu]

Hi

ok that rules that out then, unless hard water and scaling ?

maybe you can take some temps at diiferent points on the system to give us a better idea what it is doing

compressor in and out and after condensor

also air on and off condensor

the compressor sound could indicate its worn or your bringing liquid refrigerant back

R's chillerman



Thanks so much for your reply. I have noticed that the chiller brings down the first (after 2hours of rest) 0.5C in just 20mins. Then, the next 0.1C takes 30mins, the next 0.1C takes 45mins, and the next 0.1C in 1hour and so on.

I have tested the following temperatures with a digital thermometer probe.

Running time: After 30mins of continuous run from cold condition:

Air before hitting condensor: 29C
Air after hitting condensor: 43C

Compressor temp top dome: 35C (Previously when the chiller was brand new, it used to be around 65C)
Compressor temp lower dome: 31C



Running time: After 2hours of continuous run from cold condition:

Air before hitting condensor: 29C
Air after hitting condensor: 47C

Compressor temp top dome: 36C (Previously when the chiller was brand new, it used to be around 65C)
Compressor temp lower dome: 32.5C.

Thank you.

[baghu]

The water is soft here. Also it goes through demineralisation before putting in aquarium.

[chillerman2006]

Hi baghu

its hard to say without temps & pressures, was in a rush last night so was not clear

the tubes coming off the compressor is where to take temps and the tube after the condensor

really clutching at straws here, with saying either

blockage after condensor (look for temperature drop on liquid line - drier maybe)
liquid return to compressor (is there any frosting of suction line)
worn compressor

R's chillerman

[nike123]

That looks like liquid is returning from evaporator. No superheat at compressor entrance and therefore no or very little discharge superheat, and because of that, cold compressor. Someone need to take measurements of superheat and subcooling of refrigerant and some other readings (current, temperatures, pressures).
If evaporator is clean and flow is right than could be faulty TXV.


What is unit full name and model number?

[r.bartlett]

Low load/poor heat transfer/poor flow.. Check the water in/out temps it's flooding back which means you may have more dirt/scale build up than you thought..

low refrigerant or worn compressor will make the compressor run hotter not cooler.

[chillerman2006]

That looks like liquid is returning from evaporator. No superheat at compressor entrance and therefore no or very little discharge superheat, and because of that, cold compressor. Someone need to take measurements of superheat and subcooling of refrigerant and some other readings (current, temperatures, pressures).
If evaporator is clean and flow is right than could be faulty TXV.


What is unit full name and model number?


Low load/poor heat transfer/poor flow.. Check the water in/out temps it's flooding back which means you may have more dirt/scale build up than you thought..

low refrigerant or worn compressor will make the compressor run hotter not cooler.

Oh Yes !

bit slow today aren't I Gents :)

R's chillerman

[monkey spanners]

If it drops 0.5c on first 20 minutes but slows down after suspect evap is freezing up or something is happening to restrict the water flow, might be worth checking the pumps filters and pipes over incase things have started growing in there, algea, snails, little fishies etc.

Jon :)

[baghu]

Thank you chillerman
Thank you nike
Thank you r.bartlett
Thank you monkey spanners

for your fantastic advices.

All of you were right in your answers. The evaporator had indeed clogged up a lot of debris than I could ever imagine!
At first I put lots of detergent and dishwasher inside the coil. Then I let it soak for 2 hours. Then I rinsed it somewhat. Then I put 4% acetic acid in it to fully neutralize any remaining alkali. After that, I brought a 1/4th HP waterpump from my friend's house and started a huge water force through the evaporator's heat exchanger coils. Guess what? Black debris was flooding all around!
Now the chiller runs like brand new, cooling in just half an hour by a full degree and the compressor heats up to 60C max and sounds like a petrol engine! Hehe http://www.refrigeration-engineer.com/forums/images/smilies/grin.png

You all guided me, so millions of thanks to you once again! May God bless you all.

I have a question. As the compressor was flooded previously with liquid refrigerant, the lubrication may be destroyed around the cylinder and the pistons. So is the compressor going to die very soon?

[nike123]

It is probably suffered from that.

[baghu]

That looks like liquid is returning from evaporator. No superheat at compressor entrance and therefore no or very little discharge superheat, and because of that, cold compressor. Someone need to take measurements of superheat and subcooling of refrigerant and some other readings (current, temperatures, pressures).
If evaporator is clean and flow is right than could be faulty TXV.


What is unit full name and model number?

It's Resun CL-650