Emerson VH User Manual

The control system monitors both compressors and prevents each from turning on within a 3 minute 

period of being turned off. If this (on, off, on) occurs too often, ten (10) times in a one hour period, a 

Short Cycle alarm could occur.

The control allows only one load output to be energized at a time on a restoration of power or micro-

controller reset. Each additional load output will be activated at one second intervals until desired 

operating conditions have been met.

The lead compressor is the first one to be turned on when compressor operation is required. The lag 

compressor is turned on second if both compressors are required. The control monitors the operating 

time of both compressors and will automatically switch lead/lag compressor operation to maintain 

less than eight hours difference between the running times of two compressors.
When the operating hours on the lead compressor become eight hours greater than on the lag com-

pressor, the lead/lag operation is automatically switched. If the lead compressor is operating by itself 

at that time, it will be turned off, the lead/lag operation will be changed, and the new lead compressor 

will be turned on.

NOTE
If the hot gas reheat option has been selected, compressor 2 is always the lead compressor.