What is the difference between switched live and open therm?

[IaninHull]

Hello all,
Apologies A) for showing my ignorance and B) possibly asking a question that has been answered elsewhere - though I have looked!
I have a problem with the heating on a pub I have taken over. The boiler has been recently overhauled and works fine, but I'm struggling to control it. Heating on the bar is controlled by a wall mounted thermostat that works as expected. But, upstairs, which includes the flat, a large landing area, a function room and toilets, all seems to be controlled from a remote / portable thermostat in the flat. This should have 4 time/temp settings per day, but whenever I try to programme it, the 3rd option will not take any input - it just stays at --|-- regardless. What's more, even if I use the manual override and set the temp to as low as 5C overnight, or simply set it to "off", I find myself being woken up by temperatures up to 23 or 24C! The bar downstairs is staying in line with it's thermostat setting when this happens.
I've attached an image of the screen on the boiler. My questions are first - has anyone got any idea what is happening, and second, what is the difference between "switched live' and "open therm"?
TIA
Ian

 

[Vee]

Depending on the type of wireless thermostat it could be weak battery or lost communication, some fail to on. It could also be a stuck open zone valve depending on the system control set up. Switched live is on/off control, open therm is modulation in accordance with external temperature, but will need some kind of external sensor fitted, depends on what is in place. There is not enough info in your post for boiler, system and controls to conclude anything definite.

 

[IaninHull]

Depending on the type of wireless thermostat it could be weak battery or lost communication, some fail to on. It could also be a stuck open zone valve depending on the system control set up. Switched live is on/off control, open therm is modulation in accordance with external temperature, but will need some kind of external sensor fitted, depends on what is in place. There is not enough info in your post for boiler, system and controls to conclude anything definite.

Cheers Vee,
I think I changed the batteries when I first moved in, but will buy new and get that again. A plumber customer pointed to one of the zone valves as potentially u/s, again when I first moved in; the company's plumbers have since said that was not a problem...
Sorry I can't tell you more about the system - I'm on here 'cos I don't know what I'm looking at. What would happen if I switched the boiler from switched live to open therm but there wasn't an external sensor fitted?
TIA