Do we need two charge controllers

[mtoffgrid]

We have 28 panels and the original installer only installed one MidNite 150 which works just fine until below zero in winter at which time the voltage in goes above 150 and so the controller shuts off.  A new installer wants to exchange out the single 150 controller (which has been working just fine for like 10 years with the above exception) for TWO charge controllers (a 200 and a 250).  Do we need two charge controllers or can he just switch out the 150 for a single 250?  Thank you for any professional advice you can offer.

[Wizbandit]

If it were me I would look at a Hawkes Bay 90 or 120 instead of 2 Classics.  It is a newer design using newer transistors call SICFETS (Silicon Carbide).  Since you will have to rearrange the PV might as well do 2 strings of 14 modules if the VOC can be calculated to be under 600V during the winter with 14.  You may even capture more power with the newer design.  Post the info on your PV modules so we can see it is is possible.