refrigeration unit cooling capacity

[nestor_greg1220]

Hi everyone,

we have one refrigeration cabinet unit to be install and has to operate on minus (-) 25'C,cabinet temperature, it has a semi hermetic Bitzer comp.Based on the design and equipment selection the maximum distance for the unit should not exceed 20 meters length distance between the indoor and outdoor unit. but our client have changed the location and they want that the condensing unit location will be at around 45 meters.

Can you please advise, if we install the same unit in the new location,will the performance of the unit will be satisfactory??? Do you have any better suggestions???

Thank you guys in advance

Nestor_greg1220

[taz24]

Hi everyone,

it has a semi hermetic Bitzer comp.Based on the design and equipment selection the maximum distance for the unit should not exceed 20 meters length distance between the indoor and outdoor unit. but our client have changed the location and they want that the condensing unit location will be at around 45 meters.



Thank you guys in advance

Nestor_greg1220

What design and equipment selection guide?
If it is Bitzer's recommendation that the unit is less than 20mtrs distance then in my oppinion it would be foolhardy to instal it much further than that.
You need to redesign the system to alow for the added preasure drop of the extra 25mtrs or so.

Cheers taz.

[Samarjit Sen]

Generally the increase in distance would not create any problem. The only thing that has to be seen is the pipe lines should be properly laid and sized to meet the pressure drop.

[afak]

You can mount the condenser at this distance in one case : if you put the condenser at 45 m distance but install th comp separately in in a distance no more than 20 m. But you can do so to the condenser with out comp and made the discharge line and the liquid line at 45 distance using slightly wider pipes dimension for discharge and liquid line and need some arrangement for this extra discharge line .

[nestor_greg1220]

Thank you taz24
thank you Samarjit Sen
thank you afak

the compressor will not allowed by the client to be located near the indoor unit due to the heat dissipation of it.

can it be possible to reduce the pipe size of the suction line in the same 45 meters location?without changing the unit specs?

Thanks again,

nestor_greg1220

[Samarjit Sen]

Dear nestor_greg1220,

Could you please let me know the model of the Bitzer Compressor, the refrigerant being used, the capacity of the system, water cooled or air cooled, in case there is a vertical pipe then the height or a sort of stating about the pipe line layout. On the basis of this I shall be able to tell you as to the sizes and the layout you should follow to have a proper system with the proper oil return.

[PoodleHeadMikey]

The biggest problem at that low suction will be gas density - you will not be able to tolerate additional suction line pressure drop easily.

The ideal way is to arrange the suction line for 'sewer-flow' oil return. That way you can make it even larger than needed and still have good oil return without taking concern for gas velocity.

If this is impossible and you can't get both (pressure drop and gas velocity) to balance well, first; start with using a good oil separator at the compressor to keep the oil content of the liquid to the very smallest amount.

You really should be doing that anyway to keep your condenser performance at it maximum.

Either curve the line sizes yourself (which would be more satisfying - but don't forget your bends and 90's) or have Bitzer work them out for you.

PHM
--------

[TXiceman]

You will need to check the size on the liquid line and the suction line. Excess line length can lead to excessive pressure drop and reduced capacity. On the liquid line, you need to make sure you have ample subcooling to over come the line loss. On the suction line, you extra losses will really hurt capacity on low temps units, BUT if you go too large on the line, you can have oil return problems as the velocity may not be sufficient to carry the oil, especially on vertical runs.

Ken

[Samarjit Sen]

There is a very good manual on Installation and Operation of Refrigeration System by Heatcraft. The name of the manual is H-IM-64K. You can download the same from www.heatcraftrpd.com . This will help you.