HR92 "OFF" mode - does it work?

[Caesium]

Hey folks.

Well as per title really, I have an HR92 in a distant badly insulated utility room that I don't really want to be on, the temperature in there more or less follows the outdoor temperature so its just wasted energy to heat it up.

Ideally I'd want it set to about 2c just to stop the pipes freezing, but you can't do that. So I'll turn it on manually when it gets that cold, I think.

So I set it to OFF, thinking that would do the job. Not so. It still acts like its set to 5c and warms the radiator up. Surely OFF should mean OFF?

[paulockenden]

I think that's just frost protection. At 2 degrees there's still scope for the pies to freeze. (I'm sure you've seen a frozen windscreen when the car says it's 2 degrees).

P.

[DBMandrake]

"OFF" on an HR92 is still 5 degree frost protection - this is documented in the manual.

The difference between setting it to OFF and setting it to 5.0 degrees is that in OFF mode the HR92 will ignore any set point changes sent it from the main controller either by schedule or manually, it will remain set to 5 degrees at all times, whereas setting it to 5.0 degrees would allow it to be overridden by the controller.

I have to agree with Paul - setting a thermostat to 2 degrees and expecting to be protected from freezing pipes is taking a big chance. Sure it might be above 2 degrees in the room where the radiator is, but what about where the pipes run below the room ? Depending on where your pipes run they may be colder than the radiator. 5 degrees is the typically used frost protection temperature on most devices so that there is a small safety margin.

If you really don't want the HR92 opening the valve under any conditions, click the locking latch underneath across to the "open" position after you have set it to OFF mode and the motor has had time to fully close the valve. The motor will never turn when the latch is not locked and thus won't open the valve. I am not sure whether it would still call for heat wirelessly from the boiler in this condition as I have not tested that, but I suspect it won't.

I certainly don't recommend doing this though due to the risk of frozen pipes. Maintaining a room at 5 degrees doesn't use that much energy. Heat loss depends on temperature differential so maintaining a room at 5 degrees when its 0 degrees outside uses only 1/4 of the energy that maintaining it at 20 degrees would.

[Caesium]

Thanks folks, that does make sense. I'll leave it set at 5 then, so I don't lose the ability to control it remotely. OFF doesn't do what I thought it did