Index: web/sys/SearchObject/Solr.php
===================================================================
--- web/sys/SearchObject/Solr.php	(revision 4252)
+++ web/sys/SearchObject/Solr.php	(working copy)
@@ -71,6 +71,8 @@
     protected $searchSubType  = '';
     // Used to pass hidden filter queries to Solr
     protected $hiddenFilters = array();
+    // Multiselect facets
+    protected $multiSelectFacets = array();
 
     // Spelling
     protected $spellingLimit = 3;
@@ -97,6 +99,9 @@
         $this->allFacetSettings = getExtraConfigArray('facets');
         $this->facetConfig = array();
         $facetLimit = $this->getFacetSetting('Results_Settings', 'facet_limit');
+        $this->multiSelectFacets = explode(',', $this->getFacetSetting(
+        	'Results_Settings', 'multiselect_facets'
+        ));
         if (is_numeric($facetLimit)) {
             $this->facetLimit = $facetLimit;
         }
@@ -964,18 +969,33 @@
 
         // Define Filter Query
         $filterQuery = $this->hiddenFilters;
+        $orFilterQuery = array();
         foreach ($this->filterList as $field => $filter) {
             foreach ($filter as $value) {
                 // Special case -- allow trailing wildcards and ranges:
                 if (substr($value, -1) == '*'
                     || preg_match('/\[[^\]]+\s+TO\s+[^\]]+\]/', $value)
                 ) {
-                    $filterQuery[] = "$field:$value";
+                    if (in_array($field, $this->multiSelectFacets)) {
+                        $orFilterQuery[$field][] = "$field:$value";
+                    } else {
+                        $filterQuery[] = "$field:$value";
+                    }
                 } else {
-                    $filterQuery[] = "$field:\"$value\"";
+                    if (in_array($field, $this->multiSelectFacets)) {
+                        $orFilterQuery[$field][] = "$field:\"$value\"";
+                    } else {
+                        $filterQuery[] = "$field:\"$value\"";
+                    }
                 }
             }
         }
+        if(!empty($orFilterQuery)) {
+            foreach ($orFilterQuery as $field => $filter) {
+                $filterQuery[] = '{!tag=' . $field . '_filter}' 
+                    . '('. implode(" OR ", $filter) . ')';
+            }
+        }
 
         // If we are only searching one field use the DisMax handler
         //    for that field. If left at null let solr take care of it
@@ -988,6 +1008,9 @@
         if (!empty($this->facetConfig)) {
             $facetSet['limit'] = $this->facetLimit;
             foreach ($this->facetConfig as $facetField => $facetName) {
+                if (in_array($facetField, $this->multiSelectFacets)) {
+                    $facetField = '{!ex=' . $facetField . '_filter}' . $facetField;
+                }
                 $facetSet['field'][] = $facetField;
             }
             if ($this->facetOffset != null) {
Index: web/conf/facets.ini
===================================================================
--- web/conf/facets.ini	(revision 4259)
+++ web/conf/facets.ini	(working copy)
@@ -55,6 +55,8 @@
 ; If using facets at the top of search results you have more room for text.
 [Results_Settings]
 facet_limit        = 30     ; how many values should we show for each facet?
+; Specify which facet fields are multi-select (filters are OR'ed instead of AND'ed)
+;multiselect_facets = institution,building,format
 ; Rows and columns for table used by top facets
 top_rows = 2
 top_cols = 3