It seems to me that it’s part of the contract between the hotel and the guest. There is a fee for certain things like staying past the checkout time, taking a towel, breaking something or bypassing the AC controls.
We stayed in a hotel a couple of weeks ago where the thermostat was set uncomfortably high, especially in a small room with two adults and a kid. It was only going to get warmer. The thermostat controls were locked and the window couldn’t open enough to make a difference.
We called the front desk and asked if the temperature could be lowered. They said yes and programmed it from their end. The room cooled down reasonably quickly and we had a good night’s sleep.
Easy peasy.
I can understand why hotels would limit how high or low guests could set the thermostat. Otherwise, they’d have people cranking it way up or way down and then going off and leaving it that way, either because they forgot or just didn’t care or were deliberately being dicks, resulting in higher energy bills for the hotel and possibly a room that couldn’t be restored to a comfortable temperature in time for the next guest.
It seems doubtful to that any significant number of people would even want to go outside the temperature range the hotel sets. Or that they would know how to, or be sufficiently motivated to find out. I can tell you I don’t want my room below 68, so whatever.
For the few who take it as a challenge, I imagine the hotel would be happy to impose the add-on charge. They’re surely setting that amount high enough so they’re not losing money dealing with whatever they have to do afterward to get it back where it was. The miscreants can’t say they weren’t warned.
At best. Beyond extra wear and tear running an AC too low for too long invites other mechanical issues. It’s very much in the hotel’s interest that the units cycle on and off rather than running indefinitely.
One thing that can happen when the AC runs a long time is that ice can form on the coils. If the AC runs continually, the ice may completely cover the coils and block any air flow. This leads to service calls as the room gets hotter and hotter. The drain hose under the coils can also freeze up. This can cause the condensation to overflow the drain pan, which causes water damage around the pan. If someone sets the AC temp very low, it will just run continually trying to reach a temperature which is below the cooling ability. If instead the temp is set above that lower limit, the AC will cycle on and off, which gives time for the ice to melt and flow away.
And when I awoke
I was alone
This bird had flown
So, I lit a fire
Wasn’t it good, Norwegian Wood?
I worked for a district where they were tired of spending money on keeping the rooms at a comfortable temperature so they set it and put a physical shield in front of it. However, you could slide a paper clip in there and move the settings. One teacher got written up for that for violating district policy.
In my current district, it’s the same thinking however the temperature is controlled from the central office. I guaranty there would be consequences if someone hacked around it.
Heat lamp on an extension cord. All sorts of ways to spoof a school thermostat without opening the cage.
Nope. District comes down on you because like having a coffee maker or minifridge or microwave in your room, you are stealing electricity from the district.
To the OP: you couldn’t get the hotel to comp you 5 or 10 degrees? A high-roller like you?
It’s almost as if…
Play stupid games, win stupid expensive prizes …
Though I gotta confess, my college roommate and I and a couple of friends threw a beach party in our dorm room.
In January.
In Maine.
Each room had their own thermostat that had a locked but ventilated plastic box over it. This was in 1980/81 so it was a very simple unit. We just kept wrapping the box in icy cold towels and got that small corner room (with windows on two walls) to 80+ degrees! We had a great time and no expensive repercussion 
Unauthorized tampering with HVAC sounds to me like a polite hotel charge, and when you call to find out what it is for, “well, we had two guest rooms where they puked out the window!”
Just pay the bill.
It’s unclear to me too, but I’m no thermostat expert: I was just quoting the article I linked that mentioned hotel management complaining about damage caused by thermostat hackers.
While I don’t discount the possibility that hotel management may well be lying about that, I also found this explanation of potential hazards of setting a thermostat too low in an AC system:
[ETA: Oh, Johnny_Bravo and filmore already mentioned these issues.]
It wasn’t in the rules…
Who says this is illegal?
Defcon fucking rocks!
Are you certain that it wasn’t mentioned in the agreement or document you signed when you checked in?
It didn’t need to be in the rules. The fact that you could not get the thermostat below there their set minimum without tampering with it told you were not allowed to do it.