excessive suction temp

[engiraq]

hi
Iam new
pls help me I am mechanical eng. but I am new in refrigeration system I have trouble with vilter single screw comp. work with 717R (ammonia) the suction temp in normal condtion is -30c & the pressure is 0.0 kpa. but now the suction temp is -7 c & the pressure still 0.0 kpa. there is no efficiency !!,where is the broplem?? how can I fix it?

[US Iceman]

with 717R (ammonia) the suction temp in normal condtion is -30c & the pressure is 0.0 kpa. but now the suction temp is -7 c & the pressure still 0.0 kpa.


This seems like a problem of not having enough liquid in the evaporator causing higher than normal suction superheat. I am assuming the compressor is fully loaded at 100% capacity.

[engiraq]

thanks iceman ,the capacity is 100%

[US Iceman]

If the compressor is at 100% and you high suction superheat my logic (based on a very small amount of information;)) is this: there is just enough liquid entering the evaporator to keep the suction pressure high when the compressor is fully loaded. However, if the superheat starts to increase this tells me the evaporator is not fully wet with enough liquid to keep the superheat at the normal point.

Therefore, the evaporator is evaporating what liquid is present and the resulting vapor is being superheated in the evaporator (which does very little actual cooling).

How much liquid do you have in the high pressure receiver?

[Magoo]

Hi
if system is at 100% and suction is rising, your client is overloading and system cannot cope, check motor amps, air on air off evap temperatures. Discharge pressures.
Clients have a great habit of doing that and blame the system performance.
Remember "heat in equals heat out ".
magoo

[engiraq]

if you mean high pressure reciever that one contact with liquid pump it have much liquid a bove the 75% & liquid pump pressure is 4 bar its normal !!

[mattfromthecc]

Have to agree with ICEMAN, not enough liquid in the evap, if everything else in Normal.

[desA]

What would happen if the TXV were to cut back the refrigerant flow too much?

Wouldn't the evap over evaporate & hence push up the exit superheat?

[icecube51]

not enough NH³ in system ore blocking along the way back.

Ice

[Peter_1]

What would happen if the TXV were to cut back the refrigerant flow too much?

Wouldn't the evap over evaporate & hence push up the exit superheat?
TXV on a NH3?

[icecube51]

good one peter (lol)

Ice