Oa Reset; Rh Cooling Reset; Power Failure Recovery; Cool Enable - Carrier 30MP Installation And Startup Manual

Multi-chiller

Table of Contents

Sequence of Operation

OA reset

You can raise the water temperature setpoint as a function of the outdoor air temperature. If you set Cooling

Setpoint OA Reset to Enable, then as the OA temperature drops below the OAT CHW Supply Reset High Limit, the

water temperature setpoint increases proportionally between OAT CHW Supply Reset High Limit and OAT CHW

Supply Reset Low Limit. At OAT CHW Supply Reset Low Limit, the maximum reset amount, Maximum OA CHW

Reset, is added to the configured water temperature setpoint.

If Cooling Setpoint OA Reset is set to Disable, then the configured water temperature setpoint is used.

The 30MP Multi-chiller can reduce any calculated OA reset, if the sensed relative humidity is above the control

setpoint. If you set RH Cooling Setpoint Reset to Enable, as the RH increases above the Occ Relative Humidity

Setpoint, a PID calculates the amount of reduction in the OA reset value. RH Cooling Setpoint Reset is only

applicable if the OA reset is active, since it can only reduce what is calculated by that algorithm. RH Cooling

Setpoint Reset will NOT lower the water temperature setpoint below the user-defined Chilled Water Setpoint

value.

If you set RH Cooling Setpoint Reset to Disable, then the configured Chilled Water Setpoint, plus any calculated

OA reset, is the controlling setpoint.

The controller has a Power Fail Restart Delay after a power loss. You can configure the amount of time in

seconds, up to 600. When the power returns, the controller prevents operating and starting any chillers for that

amount of time.

The controller can also immediately restart the prior number of operating chillers in their previous capacity, if the

duration of a power outage was less than the configured Immediate Restart Time in minutes. The plant returns to

capacity quickly if there is a short outage and prevents waiting to load the plant at the ACR rate. This feature adds

stages every 30 seconds until the previously operating plant capacity is reached.

The controller can prevent chiller operation if the OAT is below an adjustable OA temperature. If Cool Enable is set

to Enable and there is a valid OA temperature and if the OA temperature is greater than the Cooling Lockout

Temperature, the controller actively controls the chillers as required. If the OA temperature falls below the

configured lockout value minus 2°, then all chillers are disabled.

30MP Multi-chiller

Installation and Start-up Guide

Table of Contents