mqquay screw LOW DISCHARGE superheat fault

[sweimaker]

ok

gas charge of system is unknown. r134a, it does run and cool (perhaps not efficently) but it works.

from time to time its constantly tripping on the above fault. ive slowed down fan motor speeds to raise head pressure, did seem to work, but any ambient above 21c she fails on me.

if i am completly honest the fault baffles me to what its saying..

any advice or comments on similar issues appreciated. lotsss

[RANGER1]

sweimaker could be something to do with oil temp/discharge temp being to close to saturated condensing pressure.
Normally oil/discharge temp, say on a Bitzer recommend 15 C above SCT to keep refrigerant diluting oil.

What type of oil cooling does it have, if any?

[sweimaker]

thanks fgor your reply.

both cirucits are running high oil pressures (oil and filters have been changed a month ago)

mcqauy say it should run between 1 -1.5 bar

we are running 2-2.5 (cut outs at 2.5.

if this helps

[RANGER1]

Could it be flooding back causing low discharge temps?

Have you checked superheat at compressor?

[sweimaker]

hey thanks for response guys...ok

2 circuit son chiller. circuit 1 is ok..

circuit 2 has the low discharge super heat fault

this is how far ive got

discharge leaving compressor is 55 degrees (at full duty) circuit 1 is 85

suction is 7 degress on both circuits.

whats happening is the exv is fully openning!!! 2000 pulses where as on circuit 1 full load is 0800


if any1 has an answer to why the microtech 2 aka carell controller is demanding the exv to fully open would help.. it was replaced 2 months ago possibly the computer has malfunctioned.?

same suction temps as the working circuit 1, but liquid is flooding back. i havent actually checked the suction sensor although its reading spot on with circuit 1, even though still no answer for the exv openning to completly open.,

any help i would love to hear your views

[tonybechara]

Low suction super heat fault occur whenever you have a low super heat temperature, at 100% load your discharge temperature should be arround 85c, and superheat between 30 and 35 degree, lack of rfrigerant can cause a low super heat, also liquid flooding back can cause the low superheat on mcquay chillers with screw compressors. evaporator freezing also cause oil to flood back and cause a low super heat temprature.

[Grizzly]

Tony.
Welcome to the forum, Sadly your first post may be up to 4 months to late.
It is well worth checking the date the post is added.
But good luck for the future all the same.
Grizzly.

[AlexG]

Do u have economizer or liquid injection. If yes check them.

[Sardinha]

Also check your EXV, improper setting of EXV can also cause this issues tipically from units with thermostatic EXpansion Valves.

[sinnedobi]

Hello, have you resolve that problem? What it was? I have getting the same problem. Thanks

[sinnedobi]

i resolve it , it was the exv sensor on suction pipe :-)