Reasons for High Suction super heat and low Discharge superheat

[Ashok2005]

Hi friends, We are having Macuay Chiler PEH 100 using refrigerant 134a
Please advise me the probable reasons for:-
1) High Suction Super heat.
2) Low Discharge Super heat.
Thanks.

[The Viking]

At the same time?
Poor performance of the comressor?

Care to elaborate a bit more?
Pressures/temperatures would be handy...

:cool:

P.S. One thread is plenty.

[Ashok2005]

Thanks for responding Viking. . . .no no both the problems will rarely occur simultaneously. . .I am not having any problem with the chiller Unit. . . .I have asked the question for fetching some knowledge from you guys which will help me understand a little basics. . .I have started looking these chillers recently. ..

[The Viking]

OK,

1) Poorly adjusted/functioning TEV/EEV or high heat load (=very warm water)

2) Poorly adjusted/functioning TEV/EEV, basically a low suction super heat giving too much liquid back to the compressor. OR, the discharge pressure is too low.

The normal fault on the discharge super heat is the reversed, HIGH discharge superheat which normally means that either you got a lack of refrigerant (or at least a lack of refrigerant flowing through the evaporator) or a high head pressure (for example due to a dirty condenser)

:cool:

[setrite]

+1 to The Viking.
But, In a McQuay Centrifugal the discharge superheat will mostly be low all the time as they use the liquid injection system to reduce sound level, liquid is picked up from the condenser and sprayed just behind the Impeller helping in sound reduction.

[Ashok2005]

Thanks Viking and Setrite. . .
What I understand that. . .
1) In case of High suction super heat. . .the refrigerant charge may be less or the expansion valve might be malfunctioning or the Chilled water load is more(Temp high or flow high) . . .
2) In case of Low discharge superheat. ..the refrigerant charge may be excess or the expansion valve might be malfunctioning or condenser pressure is high due to low cooling water flow or dirty condenser tubes.
Please let me know if I have understood correctly. .

[PRESS]

evrything else you said is correct except that if your water flow is low or condenser is fouled your discharge superheat goes up as well.

[mbc]

any thing can effect to evaporator capacity as same as you told about TX valve also evaporator fans - air flows from evaporator -
Also in condenser air inside system effect to our condenser capacity and it is more common problem when we repair system.

[Ashok2005]

Thanks PRESS and mbc. . . .:)