Boiler Short Cycling

Short Cycling

Boiler short cycling occurs when a boiler subject to its own internal thermostat 'fires up' - starts operating when the thermostat detects that the water in the boiler has cooled down.

For example: 

When your heating system does not require the boiler to fire, the heated water in the boiler's heat exchanger will begin to loose heat to the air around the boiler's casing and through the flue. This loss of heat is not related to any loss of heat in your home.

Short cycling is simply the boiler firing up to re-heat the water in it's own heat exchanger when that water has cooled down. Because this water heats up quickly, the temperature that the thermostat is set to is also quickly achieved and when this happens the boiler is again shut down.

The boiler can continue to fire, heating the water in the heat exchanger and shutting down for a prolonged period of time without actually producing any heat for your home.

When the boiler is running and not producing heat for your heating system this 'short cycling' is:

  1. Wasting energy - increasing your fuel bill - and
  2. Damaging to the boiler's heat exchanger from constant localized boiling

An essential part of a modern efficient central heating system is the prevention of boiler short cycling.

Preventing Short Cycling

In a fully automatic central heating system the short cycling of the boiler can be prevented by using the room thermostat/programmer and hot water cylinder thermostat to switch on the electrical supply to the boiler. This wiring arrangement is called a 'boiler interlock', meaning that the boiler can only fire when there is a demand for space heating, and/or for hot water.

A boiler interlock will:

  1. Protect the life of the boiler
  2. Save you money - and
  3. Save energy
Typical heating interlock wiring control sequenceTypical heating interlock wiring control sequence

Click here to visit online store.

Top of Boiler Short Cycling page



Search this Site for all your answers




Home Heat Loss Heat Gain Radiant Heat Central Heating Radiators UFH 
Heat Pumps GSHP's WSHP's ASHP's Solar Heating PV Systems Boilers 
Water Heaters Insulation Elec-Heaters

Terms of Use      |     Privacy     |   Contact Us

As Featured On Ezine Articles

Visitors Say

Hi, My name is Shannon and I'm one of home-heating-systems-and-solutions.com readers. I'd like to thank you for the excellent information I've found on home-heating-systems-and-solutions.com, it's one of my favorite readings on the net. Warmest Regards Shannon United States

Thanks for the advice for removing an air lock from an indirect system. Had to change an inlet on my cistern. First time I have tried any home plumbing. After draining the cold tank system air locked when I refilled the tank. Garden hose and mains pressure up the tap sorted my problems. Would not have known what to do without the advice on the site. Many thanks Sean United Kingdom.

An excellent site. I have found it very usefull. I am currently in the design phase of a new house and have be pondering which heat system to use. From your site I have been able to choose the right system. Ross New Zealand

I enjoyed your site. Pat United States

Special Offer
A must have for new parents

Baby sleep

22 February 2016 New Book Launch

We're so excited to announce the launch date of our first children book 'The Special and Talented Dog Show'.
You can pre-order now by clicking here.

To read more about our children's books, click here.