In using a LA4DT4U with a LC1D09B7 why do you need a 21V coil on the contactor instead of the normal 24v?
The Electronic Serial Timer has an internal voltage drop of around 3 volts. If the control voltage is 24V, the contactor coil will only see about 21 volts. This is a 12.5% drop so any small decrease in control voltage will take the coil out of the normal operating range. So to compensate we recommend the use of a 21 Volt coil. The voltage code is Z for 21 volt coils