Neo-pentane is not freezing in your chiller. Methanol does not stop hydrocarbons from freezing. The methanol will mix in the water phase and keep the water phase from freezing. Now lets see what could be happening.
If the chiller is not getting colder than 17, you are most likely out of refrigeration or,
you are loseing heat transfer because of tube fouling.
If your refrigeration compressor is at maximum load you need more compression. There are several indications, is the load control system either at maximum speed, the suction valve or control activated, are all the valve unloaders closed. Lots of things dependind on what type compressor you have. What is the temperature of the refrigerant leaving the chiller?
The number one fouling point is compressor oils coating and "FREEZING" on the refrigerant side. If there are heavy waxes coming in or lube oil on the gas side.
Finally, the most likely, level covering the tubes in the chiller is low or you have contaninates, like butanes, building up in the chiller.
Look at all the ins and outs (temp, flow, press, composition) to the chiller and see if they are making sense. You may want to post that information and we can check the similation. Also, what type of compressor and chiller (BKU?)
