Chillers versus packs

[Peter_1]

Hi all,

I want your comments on a subject discussed this morning.

I had a meeting wit some engineers of a multi-discipline engineering company.
We have to made an offer for the cooling of 6 switch-cupboard rooms 'with heavy frequency inverters in it) with a total capacity of 250 kW.

In the papers we got, they described 2 Carrier chillers on a water regime of 6°C/12°C. Temperature of the rooms should be +/- 24°C.

Because I don't like that much chillers because anyone can install them, even someone who never saw a chiller before in his life - in Belgium very often a plumber who only knows you if he has problems with it - i suggested that the running costs of a pack is cheaper. I had the wind complete in front of me from most of the engineers, mostly construction engineers who saw the basic principles of cooling/heating while studying.
For them cooling is just the same as heating, you have a waterflow and pumps, in the first case a burner, in the other a chiller. That's it.

I argued the following: We need +/- 45 kW/room. We did a selection for a AHU with a condition of 6/12.
So, for a condition of 6°C leaving water, we need to evaporate at 0°C.

Now, we install the same AHU but now with a direct expansion coil in it.
For the same capacity I need the cooling medium to cool down also to +/- 6°C to 5°C, so evaporating at 5°C. I gain 5K, so that's a (big) advantage (the way I see it anyway) in COP.

Any comments or other ideas?