The amount of refiners you can define in SharePoint online is limited. You basicaly need to link a property to a predefined managed property and set an alias.
Found an overview of the predefined managed properties here:
http://technet.microsoft.com/en-us/library/jj219667(v=office.15).aspx#DefaultUnusedMPs
| Managed property type | Count | Managed property characteristics | Managed property name range |
|---|---|---|---|
|
Date |
10 |
Queryable |
Date00 to Date09 |
|
Date |
20 |
Multivalued, Queryable, Refinable, Sortable, Retrievable |
RefinableDate00 to RefinableDate19 |
|
Decimal |
10 |
Queryable |
Decimal00 to Decimal09 |
|
Decimal |
10 |
Multivalued, Queryable, Refinable, Sortable, Retrievable |
RefinableDecimal00 to RefinableDecimal09 |
|
Double |
10 |
Queryable |
Double00 to Double09 |
|
Double |
10 |
Multivalued, Queryable, Refinable, Sortable, Retrievable |
RefinableDouble00 to RefinableDouble09 |
|
Integer |
50 |
Queryable |
Int00 to Int49 |
|
Integer |
50 |
Multivalued, Queryable, Refinable, Sortable, Retrievable |
RefinableInt00 to RefinableInt49 |
|
String |
100 |
Multivalued, Queryable, Refinable, Sortable, Retrievable |
RefinableString00 to RefinableString99 |
