What is Short-Cyling and Why is it Bad for My Equipment?

Short-Cycling is a condition where equipment goes on and off more than is optimal. Each time it goes on and off is called a cycle. When it comes to hot water and HVAC systems, we should aim to keep run times long and cycles to a minimum. Sometimes short-cycling occurs due to a system fault or due a mismatch between the system capacity and load.

Short-cycling when it comes to HVAC equipment is a problem for many reasons including temperature control, inadequate humidification, rapid component failure and the list goes on. Short-cycling is especially damaging to motors.

Here are some of the common conditions that can cause short-cycling:

• Safeties, Limits & Pressure Switches - safety switches provide for gap between the on and off points and this helps to prevent rapid short-cycling. A failure of one of these switches can result in the equipment burning out or failing all together

• Loss of Power - Sudden loss of power events can be very hard on motors and controls. They can even cause compressors to run backwards

• Oversizing/Low Load - Shortened run times when the heat load is low can cause a unit to short-cycle.

• Controls & Design - Controls play a big part in run times. Controls are needed to manage the gap between on and off to balance comfort and short cycling

In Summary - the best designed systems are the ones that never shuts of f- never shutting off is a good thing for system longevity and power consumption!