Emergency Mode; Figure 15: Rescue Mode Activation - Emerson Copeland EazyCool OM 501 Series Application Manuallines

2.8.4 Emergency mode

In case of controller malfunction, the unit provides an emergency operation mode. The controller
will be completely by-passed and the system will continue to run based on low pressure switch
(S7) cycling. The functionality of the high-pressure protection devices (S1 & S2) remain active for
safety.
NOTE: The low-pressure switch S7 in standard configuration is used as a safety device.
When activating the emergency running mode the cut in & cut out set points need to be
adjusted according to application requirement!
2.8.4.1 Functionality:
Rescue mode can be activated by swapping the "rescue mode switch".
There are 2 circuit breakers (S11 / S12) to activate the compressors (Digital model will perform
like fixed speed model (=100% capacity)). In emergency mode, the system operator needs to
decide if one or two compressors should be activated to provide sufficient cooling capacity.
Switching of one of the 2 compressors by help of S11 or S12 will divide in half the cooling capacity.
A time delay can be adjusted by help of relay K42 to avoid compressor cycling in rescue mode
(Factory setting = 10 minutes). If 2 compressors are activated in rescue mode (S11 & S12) both
compressors are always running in parallel. Also, the time delay is always applied to both
compressors in parallel.
The control of the compressors is done by low pressure switch S7. In standard operation mode,
the S7-switch is used as a safety device. In rescue mode, the settings must be adjusted to
installation needs. The time delay for the compressor starts as soon the cut in value of S7 is
reached. After time delay the active compressor (or both) will run with 100% cooling capacity until
low pressure cut out value S7 is reached and compressor(s) will stop.
The 2 fans are automatically activated with the rescue mode switch. A potentiometer allows
adjustment of fan speed (both in parallel). The fan adjustment must be done in a way that also
during high ambient the condensing temperature does not exceed the acceptable limits. Be careful
when reducing speed because of sound reasons. Risk of high pressure cut outs when ambient
temperature increases.

Figure 15: Rescue mode activation

2.8.4.1.1 PS1 – Setpoint adjustment low pressure switch
There is a pressure limiter for low pressure protection installed.
This device is designed per EN12263 and has an automatic reset.
In emergency mode, the PS1 is taking over the control of the suction pressure regulation. It should
be adjusted per the application needs from case to case. The factory settings of the low-pressure
limiter are defined for safety purposes, not for emergency operating conditions.
C6.1.9/0617/E 15