Operating Principle; Central Heating Mode; Domestic Hot Water Mode; Boiler Frost Protection Mode - Baxi EcoBlue Plus Combi 28 Installation And Service Manual

4 Description of the Product
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A
B C
Boiler Schematic
Layout
Key
1. Pump with Automatic Air Vent
2. Diverter Valve Assembly
3. Diverter Valve motor
4. CH System Pressure Gauge
5. Central Heating Filter
6. Domestic Hot Water Filter
7. Domestic Hot Water Priority Sensor
('Hall Effect' Sensor)
8. Domestic Hot Water NTC sensor
9. Non-return Valve
10. Hydraulic Pressure Sensor
11. Boiler Drain Tap
12. Safety Pressure Relief Valve
13. Plate Heat Exchanger
Connections:-
A – Condensate Drain
B – Heating Flow
C – Domestic Hot Water Outlet
D – Gas Inlet
E – Cold Water Inlet On/Off Valve and filter
F – Heating Return
20 EcoBlue Plus Combi
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27
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F
D
E
14. Condensate Trap
15. Gas Valve
16. Safety Thermostat (105°C)
17. Heating Flow Sensor
18. Flue Sensor
19. Boiler Adaptor
20. Primary Heat Exchanger
21. Spark Ignition Electrode
22. Burner
23. Flame Sensing Electrode
24. Air/Gas Collector
25. Return Heating Sensor
26. Fan
27. Air/Gas Venturi
28. Expansion Vessel
4.2

Operating Principle

The boiler can be set in 3 operating modes:- 'Summer'
(DHW only), 'Winter' (CH & DHW) or 'Heating Only' (CH only) by
use of the
4.2.1

Central Heating Mode

1. With a demand for heating, the pump circulates water through
the primary circuit.
2. Once the burner ignites the fan speed controls the gas rate to
maintain the heating temperature measured by the temperature
sensor.
3. When the flow temperature exceeds the setting temperature,
a 3 minute delay occurs before the burner relights automatically
(anti-cycling). The pump continues to run during this period.
4. When the demand is satisfied the burner is extinguished and
the pump continues to run for a period of 3 minutes (pump
overrun).
4.2.2

Domestic Hot Water Mode

1. Priority is given to the domestic hot water supply. A demand
at a tap or shower will override any central heating requirement.
2. The flow of water will operate the DHW Sensor (Hall Effect
1
Sensor) which requests the 3 way valve to change position. This
will allow the pump to circulate the primary water through the
3
DHW plate heat exchanger.
M
3. The burner will light automatically and the temperature of the
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domestic hot water is controlled by the temperature sensor.
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4. When the domestic hot water demand ceases the burner will
extinguish and the diverter valve will remain in the domestic hot
water mode, unless there is a demand for central heating.
4.2.3

Boiler Frost Protection Mode

1. The frost protection mode is integral to the appliance and
functions as long as there is power to the boiler, as indicated by
the standby signal
2. With CH & DHW or CH only selected, when the boiler
temperature falls below 5°C the boiler will fire until a
temperature of 30°C is reached.
3. If DHW only is selected, when the boiler CH temperature falls
below 5°C the boiler will fire until a temperature of 30°C is
reached. When the boiler DHW temperature falls below 5°C the
boiler will fire until a temperature of 7°C is reached.
4. Further protection can be incorporated by using a system
frost thermostat.
4.2.4

Pump Protection

1. This activates once a week if there has been no demand. The
pump runs for 30 seconds to prevent sticking.
button.
.
7219706 - 01 (04/15)