Trane RTHD

RTHD-SVX01D-EN 69
Installation Electrical
Condenser Water Pump Prestart time has been added to help with cold con-
denser water problems. In very cold outdoor ambients, the cooling towers
sump cold water would reach the chiller some time after the low system dif-
ferential pressure protection had run through its ignore time, and result in an
immediate shutdown and latching diagnostic. By simply starting the pump
earlier, and allowing mixing of the warmer indoor loop with the cooling
tower's sump, this problem can be avoided.
Condenser Water Flow Interlock
The CH530 shall accept an isolated contact closure input from a customer
installed proof-of-flow device such as a flow switch and customer provided
pump starter auxiliary contact for interlocking with condenser water flow.
The input shall be filtered to allow momentary openings and closings of the
switch due to turbulent water flow, etc. This shall be accomplished with a 6
seconds filtering time. The sensing voltage for the condenser water flow
switch is 115/240 VAC.
On a call for cooling after the restart inhibit timer has timed out, the CH530
shall energize the condenser water pump relay and then check the condenser
water flow switch and pump starter interlock input for flow confirmation.
Startup of the compressor will not be allowed until flow has proven.
If flow is not initially established within 1200 seconds (20 minutes) of the con-
denser pump relay energizing, an automatically resetting diagnostic "Con-
denser Water Flow Overdue" shall be generated which terminates the
prestart mode and de-energizes the condenser water pump relay This diag-
nostic is automatically reset if flow is established at any later time.
Note: This diagnostic would never automatically reset if CH530 was in con-
trol of the condenser pump through its condenser pump relay since it is com-
manded off at the time of the diagnostic. It could however reset and allow
normal chiller operation if the pump was controlled from some external
source.
Chilled Water Reset (CWR)
The MP will reset the chilled water temperature setpoint based on either
return water temperature, or outdoor air temperature. The Return Reset
option is standard, Outdoor Reset is optional.
The following is selectable:
• RESET TYPE Setpoint.
This can be set to: NO CWR, OUTDOOR AIR TEMPERATURE RESET,
RETURN WATER TEMPERATURE RESET, or CONSTANT RETURN
WATER TEMPERATURE RESET. The MP shall not permit more than one
type of reset to be selected.
• RESET RATIO Setpoints.
For outdoor air temp. reset, both positive and negative reset ratios will be
allowed.
• START RESET Setpoints.
• MAXIMUM RESET Setpoints.
The maximum resets shall be with respect to the chilled water setpoint.
When the chiller is running, if any type of CWR is enabled, the MP will step
the CWS toward the desired CWS' (based on the below equations and setup
parameters) at a rate of 1 degree F every 5 minutes until the Active CWS
equals the desired CWS'. When the chiller is not running the CWS will be