Suction Line Freezes Compressor

You said it yourself, the problem is the replaced compressor has less capacity. You need to right size the compressor to the system.

The compressor should run about 20 to 30 min. per hour, not all night long.

I can guess as to why the suction line is freezing, but I'm not 100% sure, but I think it's because your undersized compressor is not able to move the refrigerant at a quick enough rate to avoid the build up of condensation on the suction line. Try to insulate that line to improve performance.

The suction line/compressor could freez (a) if liquid flood back is there due to over charged refrigerant/over sized expansion valve (b) due to room temperature temperature is below freeing point. From what you have said, it is clear that the compressor replaced is not matching with the load, load is being over sized and it should not freez but should be over super heated provided the refrigerant charge is proper. As it is freezing, it is evident that refrigerant is over charged. I suggest you remove the refrigerant till only sweating is observed till the end of suction at compressor entering. Ofcourse then the inside temperature will not be maintained since the compressor is undersized to the load.

If i will change the expansion valve with lesser size,will it work. yes you are right compressor is over charged refrigerant is R22 i have kept suction pressur is 40psi but during day time it goes upto 45psi & dicharge pressure is 230psi & day time it goes up 275psi.can we do something to come out the problem but i can't the compressor.thanks & regards manish

Increase your superheat! First check and see if the expansion bulb is tight on the suction line! You want 10-15 degrees of superheat (on the closed swing of the valve) on the TXV. Shut the TXV down it is flooding through! Look for the suction line to sweat at the compressor not freeze. Do you have a inline receiver in the system? Do not bleed off any gas. Head pressure does not indicate you have a over charge. Do you have a sight glass in the liquid line?

You did not answer my Question on the motor amps?

Del

Respected Sir,

This is for kind information

1. Compressor details which we have right now

Make :Maneurop Recprocating Compressor,Model : MT40JH4E, serial no: TE105003886

thermally protected 380-400v 3phase 50hz Total amps 10A MAX,LR 38A and Running amps is 6.2amps

PS 18.4bar

TS Max 50c

LP Side TS Min. -35c

Refrigerant R22 , Danfoss,now days ambient temp. is morning time 40 to 42.c & noon time 47 to 50c.

2. The compressor before we had details are given below.

DWM Copeland

DLLE-301-EWL

Max oper. press H/L 28/22,5bar

Test Press. H/L 30,8/24,7bar

thanks & regards manish

Manish, I am unable to get information on your Compressor. Is it Belt driven?

If so is the running amps 6.2 and the name plate on the motor 10 amps?

Sight glass question?

Did you close down on the TXV ?

Del

Respected Sir,

Sir,this is not Belt driven compressor.On name plate mentioned is like that 10amps Max.Yes sight glass is there(Sorry i didn't mention in last post).

Please Could you tell me what is TXV? I am unable to understand.

thanks & regards manish

TXV = Thermostatic Expansion Valve, located on inlet to evaporator has temperature bulb attached to bellows on top of valve, remove nut on bottom to adjust , turn in to close valve and increase the super heat (source of your problem) 1/2 turn at a time . Wait one hour between adjustments and target is to get suction line to sweat @ compressor NOT FREEZE.

Del

ic ex

Respected Sir,

Thanks lot giving the solution i hope should work.Sir, could you tell me how

superheat is increased by closing the valve. Sir its suction pressure is 40psi & increased upto 45psi during day time.Dicharge pressure is 220psi goes upto 250psi.Shoud i do any changes with pressure i mean to say to incrase or decrease the pressure. thanks & regards Manish

FM: PENINSULA MARITIME - CHENNAI,INDIA.

SUB : REQUIRED PRICE FOR BELOW MENTIONED ITEM:

DEAR SIR,

PLEASE BE INFORM YOUR GOODSELVES THAT KINDLY GIVE US A PRICES FOR BELOW MENTIONED ITS VERRY URGENT URGENT URGENT.

AIRCONDITION COMPRESSOR DETAILS:
DANFOSS MANEUROP
RECIPROCATING COMPRESSORS
MODEL:MT40JH4E
SERIAL:NK 10 3667802
THERMAL PROTECTED:460V 3 - 60 HZ 10A MAX.
380-400V 3 - 50 HZ LR 38A
LP SIDE: PS 18.4 BAR.
PS MAX. 50 DEG. CENT
TS MIN. -35 DEG CENT.

YOUR PROMPT REPLY WILL BE MUCH APPRECIATED

TKS BRGDS / PENINSULA MARITIME,

ILYAS AHMED.( MOBILE : +91 98404 21397.) E-MAIL : penin@vsnl.net

Could we do something to come out the problem & achieve the temp. between 0 to 4c.but i can't the change the compressor.thanks & regards manish

Manish, the pressures have nothing or little to do with superheat.

By closing down on the adjustment. you are increasing the internal spring force so that the bulb that senses the suction line temperature will need go higher before it can build up the required pressure that will opens the TXV. This is your superheat setting. This, you need to do to get the max. BTU rating from the evaporator .

Del

1. Manish, More information is needed to confirm your problem.
2. What refrigerant?
3. Pressure's in PSI please, low side psi high side psi
4. Motor full load amps and running amps
5. Water cooled condenser or air cooled give condensing temp.
6. Give me these and I will tell you what your problem is.

Del

All that the presence of frost means is that the suction line or compressor is below freezing, and the moisture in the air has reached its dewpoint temperature and condensed. This condensed moisture has then frozen to ice because the temperature in the suction line is below 32°F.

I see 2 problems

1. The compressor is to small for the load and the TXV is over feeding and possibly slugging the compressor and diluting the oil. Check the superheat at the compressor suction inlet say 6 inchs from the inlet. It should be about 60 *F

hi Manish

Your old compressor has a capacity of 4000watts at 50 deg condensing and -20 evaporating.

The maneurop compressor has a capacity of 2000watts at the same conditions of 50 deg condensing and -20 evaporating.

the compressor iyou installed is half the capacity of the old one

If you fit a MT072 it will match your old one!!

A MT065 is slightly smaller than the old one and will possibly work and could save a buck$$ but i recomend matching as close to the old one as possible.

regards Ed

Dear,

B4 replacing the compressor with an undersized one, the system suppose holding a total 4Kg refrigerant. The same was recirculated @ x kg/m. Now with undersized compressor, the recirculation has comdown to x-y kg/m. The orifice of the TXV is constant n feeds same quntity of refrigerant which floods the suction and maintains a higher suction pressure which means higher room temperaure. U check what is the maximum RPM limit of the compressor and increase the rpm of the same by increasing the size of motor drive pulley by 0.5 to 0.75" dia if at present not running at its maximum rpm recommondd by the OEM at that particular tempreature and pressure. Watch your motor current against over loading. Dont try to fiddle with TXV. Otherwise there is no alternative to replace compressor of original capacity.

This subject has beeb discussed at this site several times. In cold stores & Air conditioners the cause of suction line freezing is due to flooding back of raw liquid refrigerant from evaporator either due to over charge, too over sized TXV or high speed of compressor. From what you described it seems that the compressor is not balanced to TXV. For walk in coolers, inside tem should be 4 C and for that the evaporator should operate at 8 to 12 lbs suction pressure with R 12 refrigerant. Before replacing the burnt compressor, the cause of its burnt out should have been found out.