You will need to have the second mortgage execute a subordination agreement to refinance the first fha. The helpful part is that the second mortgage can be in outer space and the fha first mortgage can be within fha lending limits for teh county. The homeowner will have a lower payment after the refinance of the old first to a new fha with the second subordinating at a CLTV that is higher than 100% CLTV.
Two improtant fha rules to consider are the fha refinancing above 100% and the CLTV limit FHA with a second mortgage.
More infor on CLTV FHA MAX