Baxi Combi 630 - Central Heating and Domestic Hot Water Production; Central Heating Mode; Domestic Hot Water Mode

4.2.3 Central heating and domestic hot water production
In boilers used for heating and for producing domestic hot water, an inte
grated plate heat exchanger heats the domestic water. The heated water
is then channelled to the heating installation or to the plate heat exchanger
via a diverter valve. A flow sensor detects that a hot water tap has been
turned on and communicates this to the printed circuit board (PCB), which
switches the diverter valve to the hot water position and activates the
pump. The diverter valve is spring-loaded but only consumes electricity
when switching from one position to another. Priority is given to domestic
hot water.
4.2.4 Central heating mode
With a demand for heating the pump circulates water through the primary
circuit.
Once the main burner ignites the fan speed controls the gas rate to main
tain the heating temperature measured by the temperature sensor.
When the flow temperature exceeds the set temperature, a 3 minute delay
occurs before the burner relights automatically (anti-cycling). The pump
continues to run during this period.
When the demand is satisfied the burner is extinguished and the pump
continues to run for a period of 3 minutes (Pump Overrun).
Key to components
1. Pump with automatic air vent
2. Boiler drain tap
3. Pressure gauge
4. Safety pressure relief valve
5. DHW flow sensor / filter / restrictor
6. DHW priority sensor
7. DHW NTC sensor
8. Hydraulic pressure switch
9. Diverter valve and motor
10. Plate heat exchanger
11. Gas valve
12. Safety thermostat
13. Heating flow sensor
14. Flue sensor
15. Flue adaptor
16. Primary heat exchanger
17. Burner / door assembly
18. Electrode
19. Air / gas collector
20. Heating return sensor
21. Fan
22. Air / gas venturi
23. Expansion vessel
Key to connections
A
Condensate drain
B
Heating flow
C
DHW outlet
D
Gas inlet
E
Cold water inlet on/off valve and filter
F
Heating return
4.2.5 Domestic hot water mode
Priority is given to the domestic hot water supply. A demand at a tap or
shower will override any central heating requirement.
The flow of water will operate the Hall Effect Sensor which requests the
diverter valve to change position. This will allow the pump to circulate the
primary water through the DHW plate heat exchanger.
Fig.6
Operating scheme (combi)
PN-0000309
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B
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4 Description of the product
20 7679306 - 1 - 10082017