What happens if house prices go down after HELOC appraisal?

[Harman N.]

Hi all,

Let's say you get an appraisal and open a HELOC, and some time later house prices in your market come down. What happens if:

1) You've already taken a draw from the line of credit

2) You haven't drawn on it

I'm guessing in case of #1, the lender doesn't do anything (unless there's an option similar to a margin call for stocks)?

But for #2, does the lender re-appraise and lower the amount you can borrow?