You can only use constants in an IF statement, no variables.
Working:
<tmpl_if name='if_condition' op='>' value='5'>
<tmpl_if name='if_condition' op='==' value='3.57'>
Not working:
<tmpl_if name='if_condition' op='>' value='{tmpl_var name='Capacity'}'>
<tmpl_if name='if_condition' op='==' value='{tmpl_var name='Capacity'}'>
I hope I could help you.
Regards,
Claus