Oil separator blocked

[chillyblue]

Hi

i have a Fujitsu 3 pipe heat recovery unit Ao90TPAMF
I have been advised the oil separators may be blocked, anyone witnessed this before?

[chemi-cool]

What went wrong with the unit?
What part of the oil separator you think is blocked?

[mbc]

Hi

if your system were dirty it is possible the drain is blocked
I saw it several times

[chillyblue]

Basically i have changed a compressor (there is three in total on the system) when i restarted the system all three compressor discharge lines were getting extremely hot, which i now believe to be caused by the internal relief valves in the compressors opening and the discharge gas going round in circles.
I then fitted an adaptor in one of the discharge lines to be able to fit a high pressure gauge line, when i started the compressor the discharge pressure went up to 500psi and then drop drown.
I have been advised the oil separators are a mesh type separator and they can block.

[mbc]

hi

you quite right
some of them has mesh
if you oil is poor quality and your head of compressor get too hot ( suction presure low = room temp. low)
you have mass burned oil on mesh
also I saw it maybe 3 or 4 times

[RANGER1]

You would think high pressure safety would/should shut machine down before 500psi???

[Glenn Moore]

Agree with Ranger the HP safety should shut the machines down well below 500 psi .If the impingement mesh tubes in the seperator became blocked to that degree they most likely would have disintegrated subjected to that pressure and unlikely to cause a blockage. Maybe the oil float assembly in the seperator is damaged or blocked causing oil to fill the separator. Check the oil return line and or fit a sight glass to prove oil is returning to the compressors from the separator,also check discharge pipework to see if there are check valves fitted which may be failing to open per compressor.

[Grizzly]

Agree with Ranger the HP safety should shut the machines down well below 500 psi[]

But not if the blockage is before the HP switch!

What is in between the discharge outlet and before the switch?
(Which is what the guys above are saying actually!)

I am assuming from what you are saying guys its the Oil Separator?
Chilly you say that you had to change a comp!
What did it fail on Mechanical or Electrical?

Has anyone ever known a small comp like this throw bracken components down the discharge line?
Only on the bigger stuff I am more used to working on, it's not unknown for a valve plate or similar to be ejected down the discharge line.
Just thinking out loud Guys!
Good Luck Chillyblue an interesting post thanks.

Grizzly

[mbc]

Hi

for action of HP it needs short time
if it blocked during this time our head pressure goes up
I saw about 400 psi .
most Chinese oil separator have a same cases

[Grizzly]

Just out of interest.
What refrigerant is the unit running on?
Grizzly

[nike123]

High pressure protection:




2. High pressure protection
When the discharge pressure increases to a high pressure (Cooling: 3.0MPa, Heating: 2.8MPa), the solenoidal valve SV4 opens to perform hot gas bypass. The opened solenoidal valve closes when the discharge pressure decreases to 2.7MPa for cooling operation and 2.3MPa for heating operation.
When the discharge pressure increases to 3.3MPa or above, All the compressors are stopped owing to the high pressure protection. In order to re-start the compressor, the discharge pressure should become low than 2.3MPa


Remove high pressure sensor (after oil separator) from pipe and check pressure at that point with your gauge.

Refrigerant diagram:
https://www.dropbox.com/s/y2odkcv71tkm4di/diagram.pdf?dl=1
(https://www.dropbox.com/s/y2odkcv71tkm4di/diagram.pdf?dl=1)
Presuming that you speak about starting unit in cooling operation!
If pressure at that point is also higher than 30 Bar ( 435 PSIG or 450 PSIA) , than both electronic expansion valves EEV1 and EEV2 are closed or Filter drier is blocked.
If not, than oil separator is blocked!

Since, as you described, bypass is working (SW4 is opening on command from HP sensor) I place my bet on drier!

If it is in heating operation, than either all indoor units EEV-s are closed or SV5 is closed or ball valve on outdoor unit pipe connection is closed.



@Grizzly
It is 407C!

[chillyblue]

Hi All

Thanks for your replies, the refrigerant is R407C. The compressor failed with a short to earth (electrical fault)
There are three compressors and the pipe flow is as follows, the smaller two compressors discharge into one oil seperator (no float, oil return is via soleniod valves which are controlled via the pcb to feed back at a controlled rate/time)
The large compressor discharges into another oil seperator (oil return via a soleniod valve which is controlled via the pcb to feed back at a controlled rate/time)
After the small oil seperators both discharge lines go into non-return valves, joining into one main discharge line, then it discharges into another main oil seperator, after this there is a hp switch, (each compressor i believe has an internal pressure relief valve.
The only reason i found the pressure was going so high was because i fitted a access port to the discharge line which revealed everything.

I was told the oil seperators are mesh type and they block, its going to be a big job to change all three seperators (as i've been advised to change all three)

Probably be advisable to fit two way drier to the liquid line.

Thanks CB

[chillyblue]

High pressure protection:




Remove high pressure sensor (after oil separator) from pipe and check pressure at that point with your gauge.

Refrigerant diagram:
https://www.dropbox.com/s/y2odkcv71tkm4di/diagram.pdf?dl=1
(https://www.dropbox.com/s/y2odkcv71tkm4di/diagram.pdf?dl=1)
Presuming that you speak about starting unit in cooling operation!
If pressure at that point is also higher than 30 Bar ( 435 PSIG or 450 PSIA) , than both electronic expansion valves EEV1 and EEV2 are closed or Filter drier is blocked.
If not, than oil separator is blocked!

Since, as you described, bypass is working (SW4 is opening on command from HP sensor) I place my bet on drier!

If it is in heating operation, than either all indoor units EEV-s are closed or SV5 is closed or ball valve on outdoor unit pipe connection is closed.



@Grizzly
It is 407C!

Hi Nike

It happens in both heating and cooling.
Good idea re removing the pressure sensor, have you changed the separators on these? do you think i need to change all three or just the two small ones? i would have thought if the two small ones are capturing everything it would struggle to get through to the main separator, the main separator looks a pig to change, i think iv'e got to take compressors out to even get to it.

Regards
CB