Hi 

just moved into a property which has this alarm

previous owner never used it so has no idea 

I was cleaning and the box it felt warm on one side I was rather concerned about that

so I unscrewed the unit wow! The alarm went off and wouldn’t stop no matter what I tried 

I tried the master code still didn’t stop I’ve had to isolate the alarm from main power 

I’ve got the user manual but it seems I need the code and no one knows what it is 

any help out there please??my goodness it was so loud 

Not much you can do as an end user if you don't know the code.

Removing the mains should have made it run on batteries and then trigger the outside siren if it's completely dead.

If not of that happened then something is broken.

Alarms need servicing regularly this may not have been done and other things maybe faulty.

Either leave it powered down or call an alarm company/engineer to service and reset everything.