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Fig.7
Operating schematic (system)
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PN-0000310
4.2.3
Heating and domestic hot water production
System boilers can provide both heating and domestic hot water.
Domestic hot water will be heated in a separate cylinder or tank by the
system primary water via a submerged coil or similar. The system controls
will prioritise the production of either heating or domestic hot water by the
operation of a diverter valve in the primary circuit.
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
maintain 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. Hydraulic pressure switch
6. Gas valve
7. Safety thermostat
8. Heating flow sensor
9. Flue sensor
10. Flue adaptor
11. Primary heat exchanger
12. Electrode
13. Air / gas collector
14. Heating return sensor
15. Burner / door assembly
16. Air / gas venturi
17. Expansion vessel
18. Fan
Key to connections
A
Condensate drain
B
Heating flow
C
Gas inlet
D
Heating return
4.2.5
Frost protection mode
Where the boiler is sited in an unheated enclosure and during periods
when the heating system is to be unused it is recommended that the
permanent live is left on to give boiler frost protection.
When the boiler temperature falls below 5° C, the boiler will fire until a
temperature of 30° C is reached.
Important
This will not protect the system !
Further protection can be incorporated by using a system frost thermostat.
4.2.6
Pump protection
If the boiler has been inactive for a period of 24 hours the pump will
automatically operate for 1 minute to prevent sticking.
4 Description of the product
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