This agreement is void if the buyer permits any persons other than our employees to render service to their heating equipment. This agreement does not cover parts damaged by water, fire, act of God, accident, tampering, or abuse. This agreement does not cover oil tank freeze-ups or liability for injury or damage resulting from the same. Our obligation to furnish any parts is subject to their availability through normal sources of supply. This agreement includes only the repair and replacement of parts specifically listed which are defective due to normal wear and may include the use of new, used, or reconditioned parts.