Basic Combination Boiler Operation
This is an extract from our Combination Boiler Handbook.
Hot Water Mode
Combination boilers work on the principle of hot water priority whereby the demand
at the tap is immediately satisfied.
Upon turning on a hot water tap the subsequent flow of water through the secondary
circuit within the boiler causes two things to occur.
- The diverter valve closes the central heating port and opens the hot water port
which provides a pathway for the primary water to be pumped to the calorifier via
the main heat exchanger.
- The secondary flow switch located on the diverter valve (this may vary depending
on combi type), is activated thus informing the boiler (electrically) that there
is a demand for hot water.
Immediately after these two actions the pump will operate producing a flow of primary
water within the boiler through the calorifier and main heat exchanger. The ignition
sequence operates next with maximum gas flow to the burner in order to fulfill the
instantaneous demand for hot water. The primary hot water now heats the secondary
water flowing through the calorifier.
Temperature control is achieved via a hot water thermistor situated on the secondary
outlet and a modulating gas valve. Water temperature is either pre-set or adjusted
by the user.