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Shinaolord
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We have two airconditioning systems in the office. For the sake of this question, let us assume the following current conditions:

• AC1 (old) outputs air of 26°C
• AC2 (new) outputs air of 18°C
• Office temperature is currently 23°C
• outside temperature is 35°C

Now as far as I know, air conditioning systems are a kind of heat pump; they transport energy through the temperature gradients $$office air > cooling coils$$$$\text{office air }> \text{cooling coils}$$ and $$outside coils > outside ambient$$$$\text{outside coils} > \text{outside ambient}$$.

Now obviously the first one doesn't hold for AC1, and as such I would say it is working in reverse: pumping energy from outside to inside the building. So for my intuition it would be better to switch off the old one until office temperature reaches 26°C, if the objective is the keep the office as cool as possible.

Is this intuition right and can it be backed up by a bit more physics calculations? My intuition says that it is the same as opening a window (and letting the warmer air in) or letting sunlight into the office by lifting the outside sunshades.

Note: I am ignoring the fact that we have a fresh air heat exchange system since that should in theory not bring any substantial energy inside.

PlasmaHH
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# Should the weaker of two air conditions be switched off?

We have two airconditioning systems in the office. For the sake of this question, let us assume the following current conditions:

• AC1 (old) outputs air of 26°C
• AC2 (new) outputs air of 18°C
• Office temperature is currently 23°C
• outside temperature is 35°C

Now as far as I know, air conditioning systems are a kind of heat pump; they transport energy through the temperature gradients $$office air > cooling coils$$ and $$outside coils > outside ambient$$.

Now obviously the first one doesn't hold for AC1, and as such I would say it is working in reverse: pumping energy from outside to inside the building. So for my intuition it would be better to switch off the old one until office temperature reaches 26°C, if the objective is the keep the office as cool as possible.

Is this intuition right and can it be backed up by a bit more physics calculations? My intuition says that it is the same as opening a window (and letting the warmer air in) or letting sunlight into the office by lifting the outside sunshades.

Note: I am ignoring the fact that we have a fresh air heat exchange system since that should in theory not bring any substantial energy inside.