Radiator

"The radiator was set at maximum."

"The radiator was set to the maximum setting."

"The radiator was set at the highest level."

"The radiator was cranked up to the highest level."

"The radiator was set at 5 so we turned it down to 2." (I'd like to use the numbers but this doesn't seem quite right.)

"The TRV (If I wanted to be more specific, I'd mention the valve.) was set to its highest heat.

I came across these on the Internet but I'm not sure if all of them are grammatical.

Could you skim these sentences and tell me if they're correct and natural?

Thank you.