Compressor going out on thermal cut out

[halfcan]

Hi,

I look after a chiller that is comprised of two circuits, each with one hitachi screw compressor.

One of the circuits will run for hours and hours, but eventually trip out and 'comp thermal trip' is displayed on the digital interface. I've proved that it's definitely the klixon breaking to bring this error up, however I haven't witnessed it cutting out with my own eyes, I'll leave it, go and do something else, check it now and then, and sometimes it can take up to a whole day to cutout. It seems to run as well as the other circuit. Here are some circuit readings from both.

Condenser coils are clean.

Compressor 1 (no problems)

Ref - R407C
Evap pressure - 4.5 BarG
Evap temp - 5°C (approx)
Suction pipe temp - 12°C
Superheat - 7K

Entering water temp - (between 12-15°C fluctuating)
Leaving water temp - 6°C (this is setpoint - and therefore operation stops when this is satisfied).

Condensing pressure - 14.5 BarG
Cond. temp - 40°C
Discharge pipe temp - 60°
Liquid line pipe temp - 30°C
Subcooling - 30K
De-superheating - 30K

Compressor running amps - approx 20-21A

1kV winding resistance check

U to V - over 1000 Giga ohms
V to W - over 1000 Giga ohms
U to W - over 1000 Giga ohms

Earth insulation check

U to earth - 800 + mega ohms
V to earth - 800 + mega ohms
W to earth - 800 + mega ohms

Compressor 2 (thermal trip error)

Ref - R407C
Evap pressure - 4.5 BarG
Evap temp - 5°C (approx)
Suction pipe temp - 12°C
Superheat - 7K

Entering water temp - (between 12-15°C fluctuating)
Leaving water temp - 6°C (this is setpoint - and therefore operation stops when this is satisfied).

Condensing pressure - 14.5 BarG
Cond. temp - 40°C
Discharge pipe temp - 60°
Liquid line pipe temp - 30°C
Subcooling - 30K
De-superheating - 30K

Compressor running amps - approx 24-29A

1kV to earth resistance check

U to V - not going over 300 mega ohms
V to W - over 1000 MEGA ohms
U to W - over 1000 MEGA ohms

U to earth - around 280 mega ohms
V to earth - 800 + mega ohms
W to earth - around 500 mega ohms


Operation wise it seems ok, therefore I'm thinking it's likely I've got an issue with the windings on compressor two.

Thoughts??

Any checks you suggest I should carry out?

Thank you

[HVACRsaurus]

http://documentatie.hdkl.nl/Koudwatermachines/SERVICEMANUAL%20RCU()E%20RHU()E%20AG2%20WG2%20CLG2%20AG2B/SM%20Service%20Manual%20-%20Chillers%20RCUE%20%20AG1.pdf

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[chemi-cool]

Hi,

I look after a chiller that is comprised of two circuits, each with one hitachi screw compressor.

One of the circuits will run for hours and hours, but eventually trip out and 'comp thermal trip' is displayed on the digital interface. I've proved that it's definitely the klixon breaking to bring this error up, however I haven't witnessed it cutting out with my own eyes, I'll leave it, go and do something else, check it now and then, and sometimes it can take up to a whole day to cutout. It seems to run as well as the other circuit. Here are some circuit readings from both.

Condenser coils are clean.

Compressor 1 (no problems)

Ref - R407C
Evap pressure - 4.5 BarG
Evap temp - 5°C (approx)
Suction pipe temp - 12°C
Superheat - 7K

Entering water temp - (between 12-15°C fluctuating)
Leaving water temp - 6°C (this is setpoint - and therefore operation stops when this is satisfied).

Condensing pressure - 14.5 BarG
Cond. temp - 40°C
Discharge pipe temp - 60°
Liquid line pipe temp - 30°C
Subcooling - 30K
De-superheating - 30K

Compressor running amps - approx 20-21A

1kV winding resistance check

U to V - over 1000 Giga ohms
V to W - over 1000 Giga ohms
U to W - over 1000 Giga ohms

Earth insulation check

U to earth - 800 + mega ohms
V to earth - 800 + mega ohms
W to earth - 800 + mega ohms

Compressor 2 (thermal trip error)

Ref - R407C
Evap pressure - 4.5 BarG
Evap temp - 5°C (approx)
Suction pipe temp - 12°C
Superheat - 7K

Entering water temp - (between 12-15°C fluctuating)
Leaving water temp - 6°C (this is setpoint - and therefore operation stops when this is satisfied).

Condensing pressure - 14.5 BarG
Cond. temp - 40°C
Discharge pipe temp - 60°
Liquid line pipe temp - 30°C
Subcooling - 30K
De-superheating - 30K

Compressor running amps - approx 24-29A

1kV to earth resistance check

U to V - not going over 300 mega ohms
V to W - over 1000 MEGA ohms
U to W - over 1000 MEGA ohms

U to earth - around 280 mega ohms
V to earth - 800 + mega ohms
W to earth - around 500 mega ohms


Operation wise it seems ok, therefore I'm thinking it's likely I've got an issue with the windings on compressor two.

Thoughts??

Any checks you suggest I should carry out?

Thank you

In such case, there is a problem inside the windings o that compressor.
I guess it is hermetic one. Only 3 wires coming out.
Just replace it and save time and future problems.

[install monkey]

hitatchi screw chemi- prob 6 wires coming out as it will be part wind or star delta :p
but as your windings aren't balanced and 1 winding to earth is much lower than the others, also increased running current- maybe try and limit capacity to 40% to prolong having to change it(reduce the running current to prevent it going out on klixon)

[Glenn Moore]

Hi halfcan
Try replacing the liquid line filter driers and oil charge before doin anything drastic and leave it running
for a few days to see if the windings resistance improves in case the system has any moisture or acid inside which the drier with any luck with may come to your rescue.
Use a quality drier like a Danfoss DM or Sporlan HH

[mbc]

Hi
Do what Mr.gelnn told
And it better change filter with anti acid core
Also check PH of oil
And check resistance of oil by megger

[Greek_engineer]

Hi
Do what Mr.gelnn told
And it better change filter with anti acid core
Also check PH of oil
And check resistance of oil by megger

oil resistance by megger??
can you explain me that procedure?

https://www.youtube.com/watch?v=_m2vObmWVXs