Emerson Liebert iCOM Manual De Usuario

SCR reheat is a type of electric reheat that provides tighter temperature control than staged electric 

reheat. SCR reheat capacity modulation is achieved by pulsing the reheat On and Off. Full capacity is 

achieved by constantly energizing the reheat. Units equipped with SCR reheat can operate in Tight or 

Standard mode. By default, cooling units with SCR reheat are factory-set to operate in Tight mode. 

The mode of operation can be set by adjusting the SCR Control Type parameter (Service Menu, Set-

points).
Tight Mode
In Tight mode, the compressors and reheats are operated at the same time to provide maximum tem-

perature control. The temperature deadband is set to zero at the factory. In a cooling unit with SCR 

reheat and two single-step compressors, the first single-step compressor is started and full reheat 

capacity is provided at 0% calculated output from the Temperature Proportional Band. As the call for 

cooling increases from 0% to 100%, the reheat capacity is slowly reduced by pulsing the reheat. At 

100% call for cooling, the reheat is deactivated and the second single-step compressor is started. As 

the call for cooling is reduced, the reheat capacity is slowly increased. When the call for cooling 

returns to 0%, the second single-step compressor is deactivated.
If the Temperature Proportional Band calculates a call for heating from 0% to -200%, the first sin-

gle-step compressor remains activated and full reheat capacity is provided. Based on the factory 

default settings, the first single-step compressor is deactivated when the control reaches -200% call 

for heating. The compressor remains deactivated until the control calls for 0% heating. The compres-

sor activation and deactivation points can be adjusted in the Service menu under Setpoints. 

Figure 20 illustrates how a cooling unit with two single-step compressors and SCR reheat operates 

when the SCR Control Type is set to Tight mode.