Where does that heat come from? [#208689]

You have a super hot 400Kg copper piece next to that bottle.

how did it become so super hot, and what can I do against it?

You can make a sweep only copper storage outside of your base and sweep it, then empty the storage and wall the copper so they wont pick it up and bring back to your base. (or you can enable dev commands and with ALT+Q you can teleport it away)

There are several way to make super hot copper. It could be heated by lava or deconstructed a hydrogen generator. And then your dupes used that copper to construct that pump you deconstructed there.

If it came from a hydrogen generator then you have 400kg more somewhere in your storages.

EDIT: Actually higher chance you had the hydrogen generator at that spot and they carried away 400kg copper somewhere else too.

Edited March 16, 2017 by Blas88

3 hours ago, Blas88 said:

If it came from a hydrogen generator then you have 400kg more somewhere in your storages.

EDIT: Actually higher chance you had the hydrogen generator at that spot and they carried away 400kg copper somewhere else too.

That explains it. Thanks.