Originally Posted by
littledan
The instructions state not to use extension cord for 2 main reasons.
1. If you undersize the extension cord you can overload it and cause a fire. The breaker must match the size of extension cord used.
2. Even if you size the cord correctly, there is a risk that the cord at some point gets pulled, yanked, moved, etc. This can cause a high resistance connection at the appliance cord to extension cord interface. This high resistance connection can cause a fire and your breaker wont do shit to protect you from this.
Source: electrical engineer/fire investigator
(Investigated this exact scenario with a small chest freezer in garage plugged in via extension cord)