Layer.php中不支持集合

I have written a magento query,

 $productCollection = Mage::getResourceModel('reports/product_collection')
        ->addCategoryFilter($category)
        ->addOrderedQty($from, $to)
        ->addAttributeToSelect('*')
        ->setStoreId($storeId)
        ->addStoreFilter($storeId)
        ->setOrder('ordered_qty', 'desc');
        $productCollection->getSelect()->limit( $limit );

This works perfectly and gives me required result, but when used in Catalog/Model/Layer.php, I'm getting an error. I think it supports only Mage::getModel('catalog/product')

How to rewrite this query and make it work in Layer.php. Any help would be great.