As Rossko said there seems to be some irritations.
The item String BoilerStatus_str which you described above has no channel to receive a state, as far as I can see.
Is there a Rule which updates the state ? Or are you talking about two different Items ?
So what you can do to test your item and the corresponding map is:
Login to the shell (via Putty) and then go to the karaf-console. Then enter the following command:
smarthome:send BoilerStatus_str 500_9
This will change the items state and the result will look like in my screenshot (basic ui) above.
[17:30:38] openhabian@openHABPi:~$ openhab-cli console
Logging in as openhab
__ _____ ____
____ ____ ___ ____ / / / / | / __ )
/ __ \/ __ \/ _ \/ __ \/ /_/ / /| | / __ |
/ /_/ / /_/ / __/ / / / __ / ___ |/ /_/ /
\____/ .___/\___/_/ /_/_/ /_/_/ |_/_____/
Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit '<ctrl-d>' or type 'system:shutdown' or 'logout' to shutdown openHAB.
openhab> smarthome:send BoilerStatus_str 500_9
Command has been sent successfully.