I have a small colony, all enclosed with walls and a single exit door. I have plenty of power and batteries and 5 heaters.
All my prisons freeze to death. What am I not understanding about heaters?
I have tried setting target temps to anything from 20 C to 40 C.
Ensure the room is actually enclosed. That means the roof too!
Ya, I double checked that. Is a floor required?
No floor needed.
When you mouse over the room, does it say 'indoor' in the bottom right of the screen?
Here's a more advanced building I have going: http://imgur.com/a/kHNMr
From the look of it, that interior space should be enclosed.
You might want to equip each bedroom with a heater as well.
For a room that size I had to use around 10 heaters to keep it stable and warm. Just add more heaters to see if that works.
I understand its a large room but he has three heaters and a cooler that has heat pumping into the same room. There is no way that room should be -2 degrees...
The main room shouldn't be -2, but I can't see where the mouse is. Those sub rooms have no heaters and are closed off, they could be -2.