When deep frying frozen french fries it takes around 4 to 5 minutes to deep fry frozen french fries.
When deep frying frozen french fries add the frozen french fries to the fryer basket while getting the temperature of the cooking oil up and then slowly lower the deep fryer basket into the cooking oil.
If you do it too fast then it may cause a splash back of the hot cooking oil so you want to lower the frozen french fries in the basket slowly into the hot cooking oil.
Then allow the french fries to deep fry for 4 to 5 minutes.
Keep an eye on them and lift the basket up and check them to see if they look done.
If they are not done enough to your liking then deep fry the french fries for another minute or so.
But most french fries are fully cooked at around 4 to 5 minutes.