Bitzer Compressor

[Stretch79]

Hello guys,

Need some help please from yourselves who have experience on a CSH7573-90Y Bitzer compressors controlled by am inverter.

Have attended a site where they are suffering from high discharge temperatures. Recently carried out a coil clean to which they dropped around 20 degrees less than normal.

However, after this they started to go above 85 degrees, aware Bitzer state higher degrees but looks like compressor keeps tripping on high temperature sensor, has a new temp sensor and motor protection module when installed, these units do suffer air recirc but only bad in the summertime, oil level is good ok. Bit lost atm.

Looking into liquid injection for these, wondered if anyone had any opinions on this?

[Stretch79]

Thought I'd add the noted running conditions.

Discharge temp - 69.4
Condensing pressure - 16.2B
Evap temperature - 13.1
Evap pressure - 4.8B
Liquid line temp 36.3
Air on condenser - 14.3
Air off condenser - 24.6

[Tycho]

Does it have an oil cooler?

I've commissioned a similar one a couple of years ago and I think we ran with 18bar discharge, no issues with the discharge temp.

[Stretch79]

Does it have an oil cooler?

I've commissioned a similar one a couple of years ago and I think we ran with 18bar discharge, no issues with the discharge temp.

Thanks Tycho, there is no liquid cooling, have plotted our readings onto a enthalpy diagram, would appear its lacking on sub cooling, so may have to adjust controls as necessary to compensate for this.

Housing of the compressor appears to be very hot to touch

[mbc]

Hi
You can go to liquid cooling or ECO .System
Both helps you to bring discharge temp down
But ECO. much better than liquid Injection

[RANGER1]

Thought I'd add the noted running conditions.

Discharge temp - 69.4
Condensing pressure - 16.2B
Evap temperature - 13.1
Evap pressure - 4.8B
Liquid line temp 36.3
Air on condenser - 14.3
Air off condenser - 24.6

Stretch,
Had a look but could not find, but discharge temperature cut out I think is 105 deg C.
Suction superheat might increase a little bit, but 69.4 degC sounds good.

Not sure what refrigerant you are using though.

Consider changing oil filter if you have not done already & if has extended pump down period can get hot.
Oil temperatures usually up to 70 deg C with or without oil cooling.

[Josip]

Thought I'd add the noted running conditions.

Discharge temp - 69.4
Condensing pressure - 16.2B
Evap temperature - 13.1
Evap pressure - 4.8B
Liquid line temp 36.3
Air on condenser - 14.3
Air off condenser - 24.6

Hi, Stretch,

this discharge temp sounds good ... which refrigerant is inside?

Condensing pressure looks high but ....
At what capacity you noticed running conditions?

Best regards, Josip

[Stretch79]

Morning all,

Sorry should of mentioned the fridge type. Appreciate all your input

It is running on R407C.

The discharge temps have crept up to 70 odd degrees C which is not bad but the housing is very hot to touch.

This is running at 100% for the compressor, the secondary compressor has failed so only one operational, have changed recirc. time to 720 secs from 360 to help limit the starts.

This suffers as most probably do at this time of year, due to lack of heat load.

New compressors, new oil charge and new filters, re manufactured by Bitzer units.

Will have to look into the ECO side of things, only looked at the injection part.

[RANGER1]

Thought I'd add the noted running conditions.

Discharge temp - 69.4
Condensing pressure - 16.2B
Evap temperature - 13.1
Evap pressure - 4.8B
Liquid line temp 36.3
Air on condenser - 14.3
Air off condenser - 24.6

Stretch,
You must have written incorrectly, as R407c more like 1.8 b low pressure.
As Josip mentioned discharge pressure high for low ambient.
Discharge temperature fine, but would be lower if discharge pressure lowered.
SCT 45 deg C in 14 deg C ambient.
I don’t think economiser would really help on low load, only if compressor 80-100 % loaded.
you do not mention room temperature or whatever this unit is cooling, which is also important.
You do not want sustain pressure any lower than necessary.
What is minimum load for compressor, 50%?
Units have worked on in the past have 7 minute LST, but your 12 minute better.

[Stretch79]

Hello Ranger,

Isn't that rather low 1.8B for R407c, would expect that pressure from R134A?

This chiller is feeding fan coil units within apartments, water cooled.

Compressor is on an inverter, used to be staged but that has been changed, believe minimum is 33% not 100% sure on this.

[RANGER1]

Hello Ranger,

Isn't that rather low 1.8B for R407c, would expect that pressure from R134A?

This chiller is feeding fan coil units within apartments, water cooled.

Compressor is on an inverter, used to be staged but that has been changed, believe minimum is 33% not 100% sure on this.

sorry Stretch, me thinking you wrote minus 13 deg C evaporator.
But now knowing water chiller, that was what We didn’t know.
Same with inverter.

14 deg C ambient, why would they need air conditioning to cool?

[Stretch79]

This is a big block of flats that is mainly glass panels so cooling is required albeit low loads high starts for the chiller.

[RANGER1]

This is a big block of flats that is mainly glass panels so cooling is required albeit low loads high starts for the chiller.

No buffer tank?
Nowhere to put one no doubt.
Crazy world, used to open a window for cooling, but to dangerous now, might fall out

[Stretch79]

No buffer tank?
Nowhere to put one no doubt.
Crazy world, used to open a window for cooling, but to dangerous now, might fall out

I know tell me about it, bloody people lol mind you have AC myself so can't complain.