View Full Version : How to Correctly Size Condensing Unit and Evaporator

09-06-2005, 08:56 PM
Ive worked out a cooling load for two Chiller rooms
The first one , the duty required is 4.32 Kw
The second is 6.29 Kw

What is the correct way to to size the condensing unit and evaporator coil using the wholesalers charts.

This has always been a grey area for me, and Im determined to get it right and learn the proper way to do it.

The third question is, how to I accurately select the orifice for the expansion valve

Thank you in advance

10-06-2005, 07:16 AM
What brand you're used to work with for the compressors and evaporators?
Brand for the TEV?

11-06-2005, 01:10 PM
For the evaporator the first question is what kind of thing are stored.
IE for unpakked meat you need a high relative humidity.
For other things a low as possible relative humidity.
For high relative hunidity you wil need a evaporator witch wil have high overheat and "high" evaporator temperature.
So you must select a bigger evaporator with bigger airflow.
on low humidities a smaller evaporator is selected to obtain lower evaporator temperatures with lower airflow.

For the compressor condensing unit rule of thumb select the desired operating evaporator pressure select the next bigger size close to what you need in total heat displacement.

Selecting a orifice is simple.
You now the total capacity, the desired range of evaporating pressure, check the orifice selecting chart op the expansionvalve manufacturer.
If you use danfoss, the selectingchart is printed on the inside of the box.


11-06-2005, 01:16 PM
What brand you're used to work with for the compressors and evaporators?
Brand for the TEV?

Hello Peter,

Condensing Unit are always Le Unite Hermetique
Expansion Valves danfoss
evaporators Friga Bohn

Product is cake mix..............in liquid form, contains flour and egg , other ingredients.........I think am looking to maintain temp of around 2Celcius in room

11-06-2005, 03:21 PM
I suppose you calculated the needed capacity.

A FHS4531 ZHR gives 4,8 kW at -7C evaporating and ambient 32C, connected to an SD062R with orifice 3 in a TES2.

A FHS4540 ZHR gives 6,08 kW at -7C evaporating and ambient 32C, connected to an SD082R with orifice 4 in a TES2.

Did the calculation for UH with their selection software, the evaporators via the catalogs I have here and the Danfoss selection also with the catalog. Danfoss also has a small software program for this.

You said you wants to maintain 2C, so assume +/- 7 to 10 K DT so evaporating at -5C to -7C. Max ambient = 32C.

We discussed this also in the past in another thread: you can make 100 calculations but will never find a condensing unit that precisely matches the evaporator and vice versa. And the given capacities are only valid as long load in the room remains the same, the ambient remains the same, the humidity doesn't change too much...in fact all parameters which changes continuous without the possibility to counteract these.

For the above proposal, it took some minutes to make the calculation. It's not worth to calculate it realy much deeper then I did, at least... that's my opinion.

11-06-2005, 07:32 PM
Thx Peter.. I appreciate yur help.
I shall cross reference, and yes I think I get the hang of it.

21-06-2005, 04:26 PM
My suggestion ( maybe common sense !) is always to get the load right to the best estimate - then do as Coolman suggests then do as Peter as put forward.....should be fine !