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.}

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 $\text{office air }> \text{cooling coils}$ and $\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.}