high coldroom temperature

[kerrcell]

Hi Guys,

I have a 2 forced fan evaporator.Client stopped equipment for a month and when started up did not go down to -18 degrees celcius but remained to -2 degrees.I asked to turn off,and started it myself again.R404A.I read the following.

Ambient temperature 22.3 celcius.
Suction pressure 22 psig/ 1.5B
Discharge pressure 175psig/11.9B
Liquid line pressure 175 psig/11.9B

Thermometre readings.

After half hour running with sight glass clear and same pressures.
Suction temp 3.8 celc
Discharge temp 65.6 celc
Liquid line temp 38.5 celc.

Air off condenser fans 26.4 celc,entering 22.3 celc.
Air off evaporator fan/s -1 deg celc.
Room temperature -1 celc.
Inspection of txv having apartial frosting of evaporator.


What can be the reason of not getting the temperature down.I asked client to await till tomoroow morning and recheck temperature.

[Brian_UK]

How long does the room normally take to pull down to temperature?

[chemi-cool]

Replace the refrigerant with a virgin one.
I have seen this hapening a few times. The best is to use 507.

[kerrcell]

This is the first time being on this plant,but left it working for 2 hours and did not drop below -2 celc from +8 celc.

[rasper]

if u have a back pressure of 1.5 Bar thats very low pressure whats is your coil temp?

[nike123]

Suction pressure of 1,5 bar is -25°C
Suction temperature is 3,8°C! Where is it measured?
At -2°C coldroom temperature evaporation temperature should be -12°C to -17°C.

Liqud line pressure 11,9 is 26°C condensation. Entering air is 22,3°C. Condensation should be at least 32-35°C.
Liquid line temperature is 38,5°C. That mean no subcooling.
You are probably short of gas!

[Sandro Baptista]

Suction pressure of 1,5 bar is -25°C
Suction temperature is 3,8°C! Where is it measured?
At -2°C coldroom temperature evaporation temperature should be -12°C to -17°C.

Liqud line pressure 11,9 is 26°C condensation. Entering air is 22,3°C. Condensation should be at least 32-35°C.
Liquid line temperature is 38,5°C. That mean no subcooling.
You are probably short of gas!

If you are short of gas so probably the compressor or the group of compressors is working at low partial capacity. Kerrcell do you confirm that?
OR only remains the two low pressure components of blend refrigerant (the R134a and the R143a) the high pressure component (R125) was gone.

[kerrcell]

Hi guys,

I read suction temperature at close to compressor,not in the evaporator.Did not take the reading inside the evaporator! I did suspect that charge is low but obviously one cannot just start filling up with gas and then will find that has to take agaain part of it away if not in full ! This morning called the client and he said that during the night temperature dropped to -5,not more.The fact that the evaporator is partially frosted,drives me to lach of charge.Will recheck with client later today,if temperature,still the same,will collect what is in system.Then evacuate and refill by new gas R404A.

[Sandro Baptista]

What's the % compressor capacity? Also if there is some kind of obstruction on the suction pipe (suction filter dirty or a valve partially close) then that will cause the present effect because the evaporating temperature would be much higher and consequently less capacity.

[baycuclaudyu]

The cold room was empty when is start to work ?

[kerrcell]

Yes the cold room was empty.I think it takes longer to drop down the temperature.Could not get in touch with client to confirm temperature but will update tomorrow.Thanks for now

[kerrcell]

Guys last night we had a total power cut whole country,will update tomorrow with temperature.

[nike123]

At -2°C coldroom temperature evaporation temperature should be -12°C to -17°C.


I made mistake here, it should be -7°C to -12°C.

[Sandro Baptista]

I made mistake here, it should be -7°C to -12°C.


...But if with a so big DT1 the suction pressure is so lower with a high superheat that really could mean short of refrigerant or other causes already pointed.

[kerrcell]

Morning Guys,

It seems all getting to the better,reading a temperature of -9 celcius.Cannot figure out what happened.I called on phone,did not visit back.I will leave it as it is for the moment and recheck.
Thanks for now.

[Sandro Baptista]

If the cold store is empty, no in/out of product it is strange that the cold store takes to long down the temperature.

How much m3 have the cold store? What kind of insulation is applied on the cold store?

[kerrcell]

The cold room is small.Measuring 8 by 8 by 7 feet high.Now temperature is -14 degrees celcius.It is old and so the insulation been never changed since.Coldroom been running around 9 years.But the compressor was changed around 4 years ago.The condenser coil has an area that is very corroded,as they washing it with tap water frequently to cool down in summer peaks !! Best thing to leave it running and see to what temperature it can drop best ! I thing there was a messup in this coldroom.

[Sandro Baptista]

hmm...when the cold room be working normally with inlets and outlets of product I doubt it will do a good job. Let see what it happen and then keep us informed.

[Peter_1]

Very important parameter you didn't gave us: SH of evaporator

[kerrcell]

Hi peter1,

Yes unfortunately did not take it.To tell you the truth,client did not bother as temperature got down more ,now reading -14 degrees celcius.He also started filling it up.He installed also plastic curtain as there not.He prefered to leave it as it is,so happy him,happy me.By the way he did not ask for bill !!!!!!!! So better keep expenses to the minimum.

[nike123]

Why would he ask for a bill? It is your work and money and you need to give him a bill, if you wish to collect money for your service.

[kerrcell]

Yep,but it looks as if I did nothing to solve his problem ! Temperature gradually went down.So best thing is to add a little extra next time I visit on something.That's better.

[Sandro Baptista]

yes, I agree we must know I to deal with the Clients...specially the one that are very "complicated".

[cold.man]

i would just for argument sakes recover refrigerant replace liquid line drier, obviously pull full vac and recharge with virgin refrigerant.
at least this will rule out if you have lost part of refrigerant blend.

then start again if problem does persist at least you have ruled out a major possible fault.

[D.D.KORANNE]

All clients are complicated .................