Chart with multiple zwave items auto created

I’d like to have a chart in my sitemap with multiple temperature inputs.
All z-wave devices are detected and items are automatically created.
I’ve created a group in my item file to be used as the chart item.
However I’m unable to add this group to the temperature items auto created.
The group shows up in habmin as a group to add but I can’t save it.
Is there any other way of doing this?
Thanks in advance