What is the temperature range between EWT and LWT in a Chiller?

Normally Range difference is5.5 to6 dec C

12.2 -6.7 (approximately) Dec C

4to6 degree temperature difference

Eg.... Let EWT 12 then LWT should be 8 degree. Is good. 

ewt - entering water temperature  50 -55 Fahrenheit lwt - leaving water temperature-42 -45 Fahrenheit.

Generally its6.7 to12 deg C. But if designer wants to decrease the air side load, it can be adjusted to5.5 to12 deg C. These two are the most common practices.