Top-Heavy Safe-Harbor

Would a top-heavy Safe-Harbor plan have to make a top-heavy minimum contribution if they only made profit-sharing contributions to non-key participants? My thoughts are no because the highest profit-sharing contribution received by a Key employee would be 0%.

Did any key employees do salary deferrals? That will trigger top heavy minimums. 

Yes a key employee did make salary deferrals as well as safe-harbor match

The Top Heavy Minimum is not determined by Nonelective Contributions alone.  As Bill Presson notes, even employee deferrals from an HCE will trigger a Top Heavy Minimum.

Isn't the top-heavy minimum covered by the safe harbor contribution?

Those eligible participants who didn't defer, and didn't therefore receive the match, would be entitled to the Top Heavy Minimum.  So have to ensure they get the PS allocation that meets the minimum.

A plan which consists solely of deferrals and safe harbor contributions is deemed not top-heavy. As soon as a dollar of profit sharing goes in to the plan - regardless of whether it goes to a key or non-key employee - the exemption is lost. Now the plan must provide the top heavy minimum.

First check the highest allocation rate to any key employee, including deferrals. If that's greater than 3%, then the top heavy minimum is 3%.

Then look at each of the non-key employees, and see how much they received in safe harbor matching contributions. If they deferred at least 3% (or 5% if a QACA), then their safe harbor match would be at least 3% and they would not need any additional employer contribution.

Then you have to give a profit sharing allocation to each of the other non-key employees who were employed on the last day of the year. If they received any match at all, then the profit sharing just has to be enough to get them to 3% match + profit sharing.

If there are any non-key HCEs that received profit sharing, then you have to test the profit sharing allocation for coverage and non-discrimination.

All of this is assuming that it agrees with your plan document. This is what the plan documents that I use say, but you have to read yours to make sure it's the same. For example, yours might give the top heavy minimum to all employees as opposed to just non-keys, or it might not have the last day requirement, or something else entirely.

I would add one thing to C.B. Zeller's comment. To be deemed not top-heavy, the plan must consist solely of deferrals and safe harbor contribution AND the eligibility requirements for both deferrals and the safe harbor contribution must be the same.