I feel silly for asking this...but I just need to be sure of myself.
We have a refinance - original loan was to purchase a mobile home (that is used at a campground on weekends), and we took a second mortgage on their primary residence.

Is it HMDA reportable?

I think it is reportable as a refi as long as you take the home again on the new loan. The new loan and the old loan must be dwelling secured in order to be reported as a refi under HMDA. Note HMDA definition of dwelling pasted in: Dwelling means a residential structure (whether or not attached to real property) located in a state of the United States of America, the District of Columbia, or the Commonwealth of Puerto Rico. The term includes an individual condominium unit, cooperative unit, or mobile or manufactured home.

Agree. If the old loan was secured by the mobile home (or another dwelling) and the new loan is secured by a dwelling and the loan is to the same borrower and the loan is not for temporary financing it would be HMDA reportable.

Both Tom and Cowboy Fan are correct. Some lenders think that the loan must be secured by the same dwelling that is being refinanced. This is not the case, if ANY dwelling secures the loan for a purchase, refinance or improvement transaction the loan is reportable.