When warranty is provided on a "parts and labour" basis a refundable deposit will be required to be paid by the customer prior to an engineer attending site to fix the item. This is to cover the cost of an engineer call out where the item is deemed to be at fault due to miss use, general wear and tear, not being maintained or the ambient temperature is of an unreasonable height.
Before paying the deposit, please make sure regular cleaning and maintenance is up to date and your unit is set at the appropriate levels to avoid the deposit becoming invalid for a refund.