Trane CGA Chiller Startup

[jogas]

I was commissioning a College Dorm job yesterday where we put in a JACE with a LON/CGA interface, and an IO-34. When it came to the CGA chiller, I found out that if the chiller sees flow before it receives a start command, it goes into alarm as it wants to control the CHW pumps. Only problem is the CGA can't do Lead/Lag/Failover for 2 pumps. Luckily I had our Electrician run 2 extra cables between the chiller and our Tridium panel. I ended up using an extra cable to bring the CGA's "Solution Pump" contact into the IO-34 as an input to enable our CHW pump logic.
I don't understand Trane's thinking, as the Solution Pump contact can be set to Run (always closed), or Auto (cycles as chiller requires). We obviously set it to Auto and the chiller startup/shutdown sequence worked fine.
Thoughts....anyone?
I forgot what Forum I was in, this post should probably be in the Commercial HVAC Forum...apologies to all.

[willf650]

The scroll chillers have been like that for several years. We always do lead/lag pumps and simply let the chiller call for the pumps. We just wire the pump contact from the chiller to the controller. My guess the main reason for that feature is the plate heat exchanger in it. Less room for error in frezzeing and rupturing the evaporator.

[jogas]

The scroll chillers have been like that for several years. We always do lead/lag pumps and simply let the chiller call for the pumps. We just wire the pump contact from the chiller to the controller. My guess the main reason for that feature is the plate heat exchanger in it. Less room for error in frezzeing and rupturing the evaporator.

Thanks for the reply.
This is the first time I've ran into having to do this.....always something
to keep you thinking.
Makes sense about the plate-frame heat exchanger.