Refinanced home acquisition debt.

Any secured debt you use to refinance home acquisition debt is treated as home acquisition debt. However, the new debt will qualify as home acquisition debt only up to the amount of the balance of the old mortgage principal just before the refinancing. Any additional debt not used to buy, build, or substantially improve a qualified home isn't home acquisition debt.

https://www.irs.gov/publications/p936#en_US_2022_publink1000229994