Yes, you can claim the mortgage interest on your home as long as you are running your microfit business.
You have to reduce the CCA on the panels/installation to the amount required to take the fit income to zero and not below.
To know how much CCA to take, enter zero on the CCA summary and check your income. Then add the total remaining income as CCA provided it is lower than the actual CCA. (You can claim CCA up to the original amount)
You can not create a business loss as long as you have CCA. Taking the mortgage interest as an expenses increases how long you will have CCA to claim. (ie any expenses reduces your CCA claim)