TD-5 Short Cycle Timer (delay on break)
If the condensing unit is not equipped with short cycle protection, a TD-5 short cycle timer should be installed. It can be located either at the condensing unit or at the furnace. The TD-5 should be wired in series with the "Y" wire (cooling control circuit). Short cycle protection is especially important for HVAC systems with zone control, since it is possible for the compressor to be cycled off by one zone and immediately cycled back on by another.