Cooler not cooling much

[jabbamonkey]

So, I placed a cooler in the wall of a sealed room (with walls and doors, the room is 12x5). I have the target temperature of the cooler set to -270 degrees.... but the outside temp is about 35 degrees, and the inside temp is only  8 degrees.  The cooler is powered, and the "current power use" is marked as "high".

Is this a bug? I can't see any reason why a target temp of -270 wouldn't lower the room sufficiently.

Also, I have no mods installed that affect the cooling and temperature.

[Apophis]

Heat is getting transfered back into the room through the walls. The target temperature does not matter too much, 0 or -270, the cooler can still only cool a certain amount.
So, just install a couple of extra coolers

[FridayBiology]

make sure that your exhaust is going to an unroofed room or to outside.

[Monkfish]

Definitely not a bug. 12 x 5 is a fairly large room to cool for a single cooler, especially if the temperature outside is 35 degrees. That size room would need at least two, maybe three, coolers to maintain a somewhat steady temperature.

[Gaesatae]

Is this a bug? I can't see any reason why a target temp of -270 wouldn't lower the room sufficiently.

Not a bug. Target temperature only determines when the cooler stop cooling, not the amount of cooling the device provides. Cooling is affected by room size and "outside temperature" at the red square of the cooler. Also, keeping the doors shut helps keeping the room cooled.