Question
QUESTION: I need to wire up a 10 hp 240 volt single phase pump that the
name plate says 45 Amp. will this require a pump controller or will a pump start relay do the same job

ANSWER: Thats quite a lot of amperage, so if it were me, I would use a pump controller with the relay in it.

---------- FOLLOW-UP ----------

QUESTION: What is the advantage of a pump controller? They cost a lot more money and I am not sure why one is needed. Someone told me that they don't stress the motor windings as much. If this is true I would like to know why.
Thanks for your help   Mike

Answer
My knowledge of the design and electrical engineering regarding pumps is limited.  I was really referring to installations that I have seen in the field, and those which I have experienced as less costly and trouble to maintain.  The pump controllers seem to work better on larger pumps (more than 5 HP) in our installations.  The pumps last longer because the electrical demand and supply are more regulated.  However, I have seen installations where there is just a relay, and they have worked, but it seems we have more trouble keeping them online.