As a result of developments in VE 2015 and the enhanced options provided the ability define the sequence in which chillers will switch on has been temporarily removed. Systems with chiller sequence ranks >1 will be reduced to 1 if the model is upgraded to VE2015.
If you wish to continue the project with the defined sequence then you can do so using the model backup which can be found in the project backups folder and can be extracted and opened in VE 2014.2.1.0. The current alternative within VE2015 is to place the sequenced chillers in separate load ranges in order to specify their operation since they can be specified to run for different load ranges and will share the load up to their individual capacities.
This is a limitation of the VE2015 version, and will be subsequently addressed. We apologise for any disruption to projects this causes an dhope the solutions provided will be adequate.