Boiler Short Cycling is when the boiler overheats and shuts off before reaching peak efficiency. If your boiler just recently started short cycling, there can be many different factors causing this issue.
If your thermostat is out of calibration your burner will be bouncing on and off. If your thermostat has a mercury switch first make sure the thermostat hangs level on the wall. Also look to see if the thermostat is in a cold draft area or possibly hanging on a poorly insulated wall. These could all be contributing factors to your thermostat getting incorrect readings. Then causing your boiler to fire inconsistently.
Air vents are crucial to your system running correctly. If your vents are clogged air will become trapped in your system and it will pressurize causing an air bubble which water wont pass through. Your boiler wont be cycling the water at this point and will overheat quickly causing it to shutoff before being able to distribute hot water throughout the house. Often this will be caught in a boiler maintenance and fixed before causing any issues.
Over sized Boilers
If your boiler is over sized it will satisfy the space heating demands too quickly, then shut down until heat is required again. This is bad because the longer your boiler runs the more efficient it will be. This can often happen when you have multiple zones in a home but only one of them is calling for heat. Therefore the amount of water flowing through the boiler is a fraction of what was expected. When you have an on-off boiler (no modulation) this becomes more prevalent and the more the boiler is over-sized, the more often it will occur. A modulating boiler does good in this circumstance because it will adjust the flame according to the load, rather then just shutting down on high limit from lack of flow.
Circulating pumps are used to force hot water from the boiler through the radiating devices such as hot water baseboards or radiators. The circulators are switched on as needed or in some cases they will be designed to run continuously. If your pump stops working it will no longer be able to circulate the water in the zone causing your boiler to overheat and begin short cycling.
Boiler Dry Cycling
When the boiler currently at the temperature set point and is in stand by mode as no further heat is required from the system load (no zones calling for heat). Due to the ambient radiated heat loses, together with the flue drought heat losses (standing losses) The boiler will naturally cool down over time which may cause the temperature controls to instruct the boiler to re fire and return the boiler back to the set point temperature. In this case the heat is not being used by the heating system it is only replacing the “standing heat loss” and therefore wasting energy.
Boiler short cycling is unhealthy overall for your system. If you have any heating issues in Northern Colorado, call Ace Hi Plumbing, Heating and Air Conditioning, Today and schedule an appointment with one of our heating servicespecialists.